Schizophrenia
Overview
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucination
Auditory hallucination
An auditory hallucination, or paracusia, is a form of hallucination that involves perceiving sounds without auditory stimulus. A common form involves hearing one or more talking voices...

s, paranoid
Paranoia
Paranoia [] is a thought process believed to be heavily influenced by anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs, or beliefs of conspiracy concerning a perceived threat towards oneself...

 or bizarre delusion
Delusion
A delusion is a false belief held with absolute conviction despite superior evidence. Unlike hallucinations, delusions are always pathological...

s, or disorganized speech and thinking
Thought disorder
In psychiatry, thought disorder or formal thought disorder is a term used to describe incomprehensible language, either speech or writing, that is presumed to reflect thinking. There are different types...

, and it is accompanied by significant social or occupational dysfunction. The onset of symptoms typically occurs in young adulthood, with a global lifetime prevalence
Prevalence
In epidemiology, the prevalence of a health-related state in a statistical population is defined as the total number of cases of the risk factor in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population...

 of about 0.3–0.7%. Diagnosis is based on observed behavior and the patient's reported experiences.
Genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

, early environment, neurobiology, and psychological
Psychology
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

 and social processes appear to be important contributory factors; some recreational and prescription drugs appear to cause or worsen symptoms. Current research is focused on the role of neurobiology, although no single isolated organic cause has been found.
Encyclopedia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucination
Auditory hallucination
An auditory hallucination, or paracusia, is a form of hallucination that involves perceiving sounds without auditory stimulus. A common form involves hearing one or more talking voices...

s, paranoid
Paranoia
Paranoia [] is a thought process believed to be heavily influenced by anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs, or beliefs of conspiracy concerning a perceived threat towards oneself...

 or bizarre delusion
Delusion
A delusion is a false belief held with absolute conviction despite superior evidence. Unlike hallucinations, delusions are always pathological...

s, or disorganized speech and thinking
Thought disorder
In psychiatry, thought disorder or formal thought disorder is a term used to describe incomprehensible language, either speech or writing, that is presumed to reflect thinking. There are different types...

, and it is accompanied by significant social or occupational dysfunction. The onset of symptoms typically occurs in young adulthood, with a global lifetime prevalence
Prevalence
In epidemiology, the prevalence of a health-related state in a statistical population is defined as the total number of cases of the risk factor in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population...

 of about 0.3–0.7%. Diagnosis is based on observed behavior and the patient's reported experiences.
Genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

, early environment, neurobiology, and psychological
Psychology
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

 and social processes appear to be important contributory factors; some recreational and prescription drugs appear to cause or worsen symptoms. Current research is focused on the role of neurobiology, although no single isolated organic cause has been found. The many possible combinations of symptoms have triggered debate about whether the diagnosis represents a single disorder or a number of discrete syndromes. Despite the etymology
Etymology
Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time.For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during...

 of the term from the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 roots skhizein (σχίζειν, "to split") and phrēn, phren- (φρήν, φρεν-; "mind"), schizophrenia does not imply a "split mind" and it is not the same as dissociative identity disorder
Dissociative identity disorder
Dissociative identity disorder is a psychiatric diagnosis and describes a condition in which a person displays multiple distinct identities , each with its own pattern of perceiving and interacting with the environment....

—also known as "multiple personality disorder" or "split personality"—a condition with which it is often confused in public perception.
The mainstay of treatment is antipsychotic
Antipsychotic
An antipsychotic is a tranquilizing psychiatric medication primarily used to manage psychosis , particularly in schizophrenia and bipolar disorder. A first generation of antipsychotics, known as typical antipsychotics, was discovered in the 1950s...

 medication, which primarily suppresses dopamine
Dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...

 (and sometimes serotonin
Serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...

) receptor
Receptor (biochemistry)
In biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...

 activity. Psychotherapy
Psychotherapy
Psychotherapy is a general term referring to any form of therapeutic interaction or treatment contracted between a trained professional and a client or patient; family, couple or group...

 and vocational and social rehabilitation are also important in treatment. In more serious cases—where there is risk to self and others—involuntary hospitalization may be necessary, although hospital stays are now shorter and less frequent than they once were.
The disorder is thought mainly to affect cognition
Cognition
In science, cognition refers to mental processes. These processes include attention, remembering, producing and understanding language, solving problems, and making decisions. Cognition is studied in various disciplines such as psychology, philosophy, linguistics, and computer science...

, but it also usually contributes to chronic problems with behavior and emotion. People with schizophrenia are likely to have additional (comorbid
Comorbidity
In medicine, comorbidity is either the presence of one or more disorders in addition to a primary disease or disorder, or the effect of such additional disorders or diseases.- In medicine :...

) conditions, including major depression and anxiety disorder
Anxiety disorder
Anxiety disorder is a blanket term covering several different forms of abnormal and pathological fear and anxiety. Conditions now considered anxiety disorders only came under the aegis of psychiatry at the end of the 19th century. Gelder, Mayou & Geddes explains that anxiety disorders are...

s; the lifetime occurrence of substance abuse
Substance abuse
A substance-related disorder is an umbrella term used to describe several different conditions associated with several different substances .A substance related disorder is a condition in which an individual uses or abuses a...

 is almost 50%. Social problems, such as long-term unemployment, poverty and homelessness, are common. The average life expectancy
Life expectancy
Life expectancy is the expected number of years of life remaining at a given age. It is denoted by ex, which means the average number of subsequent years of life for someone now aged x, according to a particular mortality experience...

 of people with the disorder is 12 to 15 years less than those without, the result of increased physical health problems and a higher suicide
Suicide
Suicide is the act of intentionally causing one's own death. Suicide is often committed out of despair or attributed to some underlying mental disorder, such as depression, bipolar disorder, schizophrenia, alcoholism, or drug abuse...

 rate (about 5%).

Symptoms

A person diagnosed with schizophrenia may experience hallucination
Hallucination
A hallucination, in the broadest sense of the word, is a perception in the absence of a stimulus. In a stricter sense, hallucinations are defined as perceptions in a conscious and awake state in the absence of external stimuli which have qualities of real perception, in that they are vivid,...

s (most reported are hearing voices
Auditory hallucination
An auditory hallucination, or paracusia, is a form of hallucination that involves perceiving sounds without auditory stimulus. A common form involves hearing one or more talking voices...

), delusion
Delusion
A delusion is a false belief held with absolute conviction despite superior evidence. Unlike hallucinations, delusions are always pathological...

s (often bizarre or persecutory
Persecutory delusions
Persecutory delusions are a delusional condition in which the affected person believes they are being persecuted...

 in nature), and disorganized thinking and speech
Thought disorder
In psychiatry, thought disorder or formal thought disorder is a term used to describe incomprehensible language, either speech or writing, that is presumed to reflect thinking. There are different types...

. The latter may range from loss of train of thought, to sentences only loosely connected in meaning, to incoherence known as word salad in severe cases. Social withdrawal, sloppiness of dress and hygiene, and loss of motivation and judgment are all common in schizophrenia.
There is often an observable pattern of emotional difficulty, for example lack of responsiveness. Impairment in social cognition
Social cognition
Social cognition is the encoding, storage, retrieval, and processing, in the brain, of information relating to conspecifics, or members of the same species. At one time social cognition referred specifically to an approach to social psychology in which these processes were studied according to the...

 is associated with schizophrenia, as are symptoms of paranoia
Paranoia
Paranoia [] is a thought process believed to be heavily influenced by anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs, or beliefs of conspiracy concerning a perceived threat towards oneself...

; social isolation
Social isolation
Social isolation refers to a lack of contact with society for members of social species. There may be many causes and individuals in numerous generally social species are isolated at times, it need not be a pathological condition. In human society, in those cases where it is viewed as a pathology,...

 commonly occurs. In one uncommon subtype, the person may be largely mute, remain motionless in bizarre postures, or exhibit purposeless agitation, all signs of catatonia
Catatonia
Catatonia is a state of neurogenic motor immobility, and behavioral abnormality manifested by stupor. It was first described in 1874: Die Katatonie oder das Spannungsirresein ....

.

Late adolescence and early adulthood are peak periods for the onset of schizophrenia, critical years in a young adult's social and vocational development. In 40% of men and 23% of women diagnosed with schizophrenia the condition manifested itself before the age of 19. To minimize the developmental disruption associated with schizophrenia, much work has recently been done to identify and treat the prodromal (pre-onset)
Prodrome
In medicine, a prodrome is an early symptom that might indicate the start of a disease before specific symptoms occur. It is derived from the Greek word prodromos or precursor...

 phase of the illness, which has been detected up to 30 months before the onset of symptoms. Those who go on to develop schizophrenia may experience transient or self-limiting psychotic symptoms and the non-specific symptoms of social withdrawal, irritability, dysphoria
Dysphoria
Dysphoria is medically recognized as a mental and emotional condition in which a person experiences intense feelings of depression, discontent and indifference to the world around them.Mood disorders can induce dysphoria, often with a heightened risk of suicide, especially in...

, and clumsiness during the prodromal phase.

Schneiderian classification

The psychiatrist Kurt Schneider
Kurt Schneider
Kurt Schneider was a German psychiatrist known largely for his writing on the diagnosis and understanding of schizophrenia.-Biography:...

 (1887–1967) listed the forms of psychotic symptoms that he thought distinguished schizophrenia from other psychotic disorders. These are called first-rank symptoms or Schneider's first-rank symptoms. They include delusions of being controlled by an external force; the belief that thoughts are being inserted into or withdrawn from one's conscious mind; the belief that one's thoughts are being broadcast to other people; and hearing hallucinatory voices that comment on one's thoughts or actions or that have a conversation with other hallucinated voices. Although they have significantly contributed to the current diagnostic criteria, the specificity
Sensitivity and specificity
Sensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...

 of first-rank symptoms has been questioned. A review of the diagnostic studies conducted between 1970 and 2005 found that they allow neither a reconfirmation nor a rejection of Schneider's claims, and suggested that first-rank symptoms be de-emphasized in future revisions of diagnostic systems.

Positive and negative symptoms

Schizophrenia is often described in terms of positive and negative (or deficit) symptoms. Positive symptoms are those that most individuals do not normally experience but are present in people with schizophrenia. They can include delusions, disordered thoughts and speech, and tactile, auditory
Auditory hallucination
An auditory hallucination, or paracusia, is a form of hallucination that involves perceiving sounds without auditory stimulus. A common form involves hearing one or more talking voices...

, visual, olfactory and gustatory hallucinations, typically regarded as manifestations of psychosis. Hallucinations are also typically related to the content of the delusional theme. Positive symptoms generally respond well to medication.
Negative symptoms are deficits of normal emotional responses or of other thought processes, and respond less well to medication. They commonly include flat or blunted affect
Blunted affect
Blunted affect is the scientific term describing a lack of emotional reactivity on the part of an individual. It is manifest as a failure to express feelings either verbally or non-verbally, even when talking about issues that would normally be expected to engage the emotions...

 and emotion, poverty of speech (alogia
Alogia
In psychology, alogia , or poverty of speech, is a general lack of additional, unprompted content seen in normal speech. As a symptom, it is commonly seen in patients suffering from schizophrenia, and is considered as a negative symptom...

), inability to experience pleasure (anhedonia
Anhedonia
In psychology and psychiatry, anhedonia is defined as the inability to experience pleasure from activities usually found enjoyable, e.g. hobbies, exercise, social interaction or sexual activity....

), lack of desire to form relationships (asociality
Asociality
Asociality is a symptom frequently observed in schizophrenia patients. It is characterised by an inability to 'empathise', to feel intimacy with, or to form close relationships with others ....

), and lack of motivation (avolition
Avolition
Avolition is a psychological state characterized by general lack of drive, or motivation to pursue meaningful goals. A person may show little participation in work or have little interest in socializing. They may sit still for long periods of time...

). Research suggests that negative symptoms contribute more to poor quality of life, functional disability, and the burden on others than do positive symptoms. People with prominent negative symptoms often have a history of poor adjustment before the onset of illness, and response to medication is often limited.

Causes

A combination of genetic and environmental factor
Environmental factor
Environmental factor or ecological factor or ecofactor is any factor, abiotic or biotic, that influences living organisms.- Environmental factors inducing diseases :...

s play a role in the development of schizophrenia. People with a family history of schizophrenia who suffer a transient or self-limiting psychosis have a 20–40% chance of being diagnosed one year later.

Genetic

Estimates of heritability
Heritability
The Heritability of a population is the proportion of observable differences between individuals that is due to genetic differences. Factors including genetics, environment and random chance can all contribute to the variation between individuals in their observable characteristics...

 vary because of the difficulty in separating the effects of genetics and the environment. The greatest risk for developing schizophrenia is having a first-degree relative with the disease (risk is 6.5%); more than 40% of monozygotic twins of those with schizophrenia are also affected. It is likely that many genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...

 are involved, each of small effect. Many possible candidates have been proposed, including specific copy number variations, NOTCH4
NOTCH4
Neurogenic locus notch homolog protein 4 is a protein that in humans is encoded by the NOTCH4 gene.-Further reading:...

 and histone protein loci. A number of genome-wide associations
Genome-wide association study
In genetic epidemiology, a genome-wide association study , also known as whole genome association study , is an examination of many common genetic variants in different individuals to see if any variant is associated with a trait...

 such as zinc finger protein 804A
Zinc finger protein 804A
Zinc finger protein 804A or ZNF804A is a human protein that has a zinc finger in its structure.-Clinical significance:In a genome-wide study conducted in 2008, the rs1344706 SNP of the gene was shown to associate with schizophrenia...

 have also been linked. There appears to be significant overlap in the genetics of schizophrenia and bipolar disorder
Bipolar disorder
Bipolar disorder or bipolar affective disorder, historically known as manic–depressive disorder, is a psychiatric diagnosis that describes a category of mood disorders defined by the presence of one or more episodes of abnormally elevated energy levels, cognition, and mood with or without one or...

.

Assuming a hereditary basis, one question from evolutionary psychology
Evolutionary psychology
Evolutionary psychology is an approach in the social and natural sciences that examines psychological traits such as memory, perception, and language from a modern evolutionary perspective. It seeks to identify which human psychological traits are evolved adaptations, that is, the functional...

 is why genes that increase the likelihood of psychosis evolved, assuming the condition would have been maladaptive from an evolutionary point of view. One theory implicates genes involved in the evolution of language and human nature
Human nature
Human nature refers to the distinguishing characteristics, including ways of thinking, feeling and acting, that humans tend to have naturally....

, but so far all theories have been disproved or remain unsubstantiated.

Environment

Environmental factors associated with the development of schizophrenia include the living environment, drug use and prenatal stressors. Parenting style seems to have no effect, although people with supportive parents do better than those with critical parents. Living in an urban environment during childhood or as an adult has consistently been found to increase the risk of schizophrenia by a factor of two, even after taking into account drug use
Recreational drug use
Recreational drug use is the use of a drug, usually psychoactive, with the intention of creating or enhancing recreational experience. Such use is controversial, however, often being considered to be also drug abuse, and it is often illegal...

, ethnic group
Ethnic group
An ethnic group is a group of people whose members identify with each other, through a common heritage, often consisting of a common language, a common culture and/or an ideology that stresses common ancestry or endogamy...

, and size of social group. Other factors that play an important role include social isolation
Social isolation
Social isolation refers to a lack of contact with society for members of social species. There may be many causes and individuals in numerous generally social species are isolated at times, it need not be a pathological condition. In human society, in those cases where it is viewed as a pathology,...

 and immigration related to social adversity, racial discrimination, family dysfunction, unemployment, and poor housing conditions. There is evidence that childhood experiences of abuse or trauma are risk factors for a diagnosis of schizophrenia later in life.

Substance abuse

A number of drugs have been associated with the development of schizophrenia, including cannabis
Cannabis
Cannabis is a genus of flowering plants that includes three putative species, Cannabis sativa, Cannabis indica, and Cannabis ruderalis. These three taxa are indigenous to Central Asia, and South Asia. Cannabis has long been used for fibre , for seed and seed oils, for medicinal purposes, and as a...

, cocaine
Cocaine
Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...

, and amphetamines. About half of those with schizophrenia use drugs and/or alcohol excessively. The role of cannabis could be causal, but other drugs may be used only as coping mechanisms to deal with depression, anxiety, boredom, and loneliness.

Cannabis is associated
Association (statistics)
In statistics, an association is any relationship between two measured quantities that renders them statistically dependent. The term "association" refers broadly to any such relationship, whereas the narrower term "correlation" refers to a linear relationship between two quantities.There are many...

 with a dose-dependent
Dose-response relationship
The dose-response relationship, or exposure-response relationship, describes the change in effect on an organism caused by differing levels of exposure to a stressor after a certain exposure time...

 increase in the risk of developing a psychotic disorder. Frequent use has been correlated with twice the risk of psychosis and schizophrenia; however, the causality of this link has been questioned, and it remains controversial. Amphetamine, cocaine, and to a lesser extent alcohol, can result in psychosis that presents very similarly to schizophrenia. Although not generally believed to be a cause of schizophrenia, schizophrenics as a group use nicotine
Nicotine
Nicotine is an alkaloid found in the nightshade family of plants that constitutes approximately 0.6–3.0% of the dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves...

 at much greater rates than the general population.

Prenatal

Factors such as hypoxia and infection, or stress and malnutrition in the mother during fetal development
Fetal development
Prenatal or antenatal development is the process in which a human embryo or fetus gestates during pregnancy, from fertilization until birth. Often, the terms fetal development, foetal development, or embryology are used in a similar sense.After fertilization the embryogenesis starts...

, may result in a slight increase in the risk of schizophrenia later in life. People diagnosed with schizophrenia are more likely to have been born in winter or spring (at least in the northern hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

), which may be a result of increased rates of viral exposures in utero
In utero
In utero is a Latin term literally meaning "in the womb". In biology, the phrase describes the state of an embryo or fetus. In legal contexts, the phrase is used to refer to unborn children. Under common law, unborn children are still considered to exist for property transfer purposes.-See also:*...

. This difference is about 5 to 8%.

Mechanisms

A number of attempts have been made to explain the link between altered brain function and schizophrenia. One of the most common is the dopamine hypothesis
Dopamine hypothesis of schizophrenia
The dopamine hypothesis of schizophrenia or the dopamine hypothesis of psychosis is a model attributing symptoms of schizophrenia to a disturbed and hyperactive dopaminergic signal transduction. The model draws evidence from the observation that a large number of antipsychotics have...

, which attributes psychosis to the mind's faulty interpretation of the misfiring of dopaminergic neurons
Dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...

.

Psychological

Many psychological mechanisms have been implicated in the development and maintenance of schizophrenia. Cognitive bias
Cognitive bias
A cognitive bias is a pattern of deviation in judgment that occurs in particular situations. Implicit in the concept of a "pattern of deviation" is a standard of comparison; this may be the judgment of people outside those particular situations, or may be a set of independently verifiable...

es have been identified in those with the diagnosis or those at risk, especially when under stress or in confusing situations. Some cognitive features may reflect global neurocognitive deficits such as memory loss, while others may be related to particular issues and experiences.

Despite a demonstrated appearance of "blunted affect", recent findings indicate that many individuals diagnosed with schizophrenia are emotionally responsive, particularly to stressful or negative stimuli, and that such sensitivity may cause vulnerability to symptoms or to the disorder. Some evidence suggests that the content of delusional beliefs and psychotic experiences can reflect emotional causes of the disorder, and that how a person interprets such experiences can influence symptomatology. The use of "safety behaviors
Safety
Safety is the state of being "safe" , the condition of being protected against physical, social, spiritual, financial, political, emotional, occupational, psychological, educational or other types or consequences of failure, damage, error, accidents, harm or any other event which could be...

" to avoid imagined threats may contribute to the chronicity
Chronic (medicine)
A chronic disease is a disease or other human health condition that is persistent or long-lasting in nature. The term chronic is usually applied when the course of the disease lasts for more than three months. Common chronic diseases include asthma, cancer, diabetes and HIV/AIDS.In medicine, the...

 of delusions. Further evidence for the role of psychological mechanisms comes from the effects of psychotherapies on symptoms of schizophrenia.

Neurological

Those with a diagnosis of schizophrenia have changes in both brain structure and chemistry. Studies using neuropsychological test
Neuropsychological test
Neuropsychological tests are specifically designed tasks used to measure a psychological function known to be linked to a particular brain structure or pathway. Tests are used for research into brain function and in a clinical setting for the diagnosis of deficits. They usually involve the...

s and brain imaging technologies such as fMRI
Functional magnetic resonance imaging
Functional magnetic resonance imaging or functional MRI is a type of specialized MRI scan used to measure the hemodynamic response related to neural activity in the brain or spinal cord of humans or other animals. It is one of the most recently developed forms of neuroimaging...

 and PET
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...

 to examine functional differences in brain activity have shown that differences seem to most commonly occur in the frontal lobe
Frontal lobe
The frontal lobe is an area in the brain of humans and other mammals, located at the front of each cerebral hemisphere and positioned anterior to the parietal lobe and superior and anterior to the temporal lobes...

s, hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...

 and temporal lobe
Temporal lobe
The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....

s. Reductions in brain volume, smaller than those found in Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...

, have been reported in areas of the frontal cortex and temporal lobes. It is uncertain whether these volumetric changes are progressive or preexist prior to the onset of the disease. These differences have been linked to the neurocognitive deficits often associated with schizophrenia. Because neural circuits are altered, it has alternatively been suggested that schizophrenia should be thought of as a collection of neurodevelopmental disorders.

Particular attention has been paid to the function of dopamine in the mesolimbic pathway
Mesolimbic pathway
The mesolimbic pathway is one of the dopaminergic pathways in the brain. The pathway begins in the ventral tegmental area of the midbrain and connects to the limbic system via the nucleus accumbens, the amygdala, and the hippocampus as well as to the medial prefrontal cortex...

 of the brain. This focus largely resulted from the accidental finding that phenothiazine
Phenothiazine
Phenothiazine is an organic compound that occurs in various antipsychotic and antihistaminic drugs. It has the formula S2NH. This yellow tricyclic compound is soluble in acetic acid, benzene, and ether. The compound is related to the thiazine-class of heterocyclic compounds...

 drugs, which block dopamine function, could reduce psychotic symptoms. It is also supported by the fact that amphetamines, which trigger the release of dopamine, may exacerbate the psychotic symptoms in schizophrenia. The influential dopamine hypothesis of schizophrenia proposed that excessive activation of D2 receptors
Dopamine receptor D2
Dopamine receptor D2, also known as D2R, is a protein that, in humans, is encoded by the DRD2 gene.- Function :This gene encodes the D2 subtype of the dopamine receptor. This G protein-coupled receptor inhibits adenylyl cyclase activity...

 was the cause of (the positive symptoms of) schizophrenia. Although postulated for about 20 years based on the D2 blockade effect common to all antipsychotics, it was not until the mid-1990s that PET
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...

 and SPET imaging studies provided supporting evidence. The dopamine hypothesis is now thought to be simplistic, partly because newer antipsychotic medication (atypical antipsychotic
Atypical antipsychotic
The atypical antipsychotics are a group of antipsychotic tranquilizing drugs used to treat psychiatric conditions. Some atypical antipsychotics are FDA approved for use in the treatment of schizophrenia...

 medication) can be just as effective as older medication (typical antipsychotic
Typical antipsychotic
Typical antipsychotics are a class of antipsychotic drugs first developed in the 1950s and used to treat psychosis...

 medication), but also affects serotonin
Serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...

 function and may have slightly less of a dopamine blocking effect.

Interest has also focused on the neurotransmitter glutamate and the reduced function of the NMDA glutamate receptor
NMDA receptor
The NMDA receptor , a glutamate receptor, is the predominant molecular device for controlling synaptic plasticity and memory function....

 in schizophrenia, largely because of the abnormally low levels of glutamate receptor
Glutamate receptor
Glutamate receptors are synaptic receptors located primarily on the membranes of neuronal cells. Glutamate is one of the 20 amino acids used to assemble proteins and as a result is abundant in many areas of the body, but it also functions as a neurotransmitter and is particularly abundant in the...

s found in the postmortem brains of those diagnosed with schizophrenia, and the discovery that glutamate-blocking drugs such as phencyclidine
Phencyclidine
Phencyclidine , commonly initialized as PCP and known colloquially as angel dust, is a recreational dissociative drug...

 and ketamine
Ketamine
Ketamine is a drug used in human and veterinary medicine. Its hydrochloride salt is sold as Ketanest, Ketaset, and Ketalar. Pharmacologically, ketamine is classified as an NMDA receptor antagonist...

 can mimic the symptoms and cognitive problems associated with the condition. Reduced glutamate function is linked to poor performance on tests requiring frontal lobe and hippocampal function, and glutamate can affect dopamine function, both of which have been implicated in schizophrenia, have suggested an important mediating (and possibly causal) role of glutamate pathways in the condition. But positive symptoms fail to respond to glutamatergic medication.

Diagnosis

Schizophrenia is diagnosed based on criteria in either the American Psychiatric Association
American Psychiatric Association
The American Psychiatric Association is the main professional organization of psychiatrists and trainee psychiatrists in the United States, and the most influential worldwide. Its some 38,000 members are mainly American but some are international...

's Diagnostic and Statistical Manual of Mental Disorders
Diagnostic and Statistical Manual of Mental Disorders
The Diagnostic and Statistical Manual of Mental Disorders is published by the American Psychiatric Association and provides a common language and standard criteria for the classification of mental disorders...

, version DSM-IV-TR, or the World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

's International Statistical Classification of Diseases and Related Health Problems
ICD
The International Statistical Classification of Diseases and Related Health Problems is a medical classification that provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances, and external causes of injury or disease...

, the ICD-10. These criteria use the self-reported experiences of the person and reported abnormalities in behavior, followed by a clinical assessment by a mental health professional
Mental health professional
A mental health professional is a health care practitioner who offers services for the purpose of improving an individual's mental health or to treat mental illness. This broad category includes psychiatrists, clinical psychologists, clinical social workers, psychiatric nurses, mental health...

. Symptoms associated with schizophrenia occur along a continuum in the population and must reach a certain severity before a diagnosis is made. As of 2009 there is no objective test.

Criteria

The ICD-10 criteria are typically used in European countries, while the DSM-IV-TR criteria are used in the United States and the rest of the world, and are prevailing in research studies. The ICD-10 criteria put more emphasis on Schneiderian first-rank symptoms. In practice, agreement between the two systems is high.

According to the revised fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR), to be diagnosed with schizophrenia, three diagnostic criteria must be met:
  1. Characteristic symptoms: Two or more of the following, each present for much of the time during a one-month period (or less, if symptoms remitted with treatment).
    • Delusions
    • Hallucinations
    • Disorganized speech, which is a manifestation of formal thought disorder
      Thought disorder
      In psychiatry, thought disorder or formal thought disorder is a term used to describe incomprehensible language, either speech or writing, that is presumed to reflect thinking. There are different types...

    • Grossly disorganized behavior (e.g. dressing inappropriately, crying frequently) or catatonic behavior
    • Negative symptoms: Blunted affect (lack or decline in emotional response), alogia (lack or decline in speech), or avolition (lack or decline in motivation)
    If the delusions are judged to be bizarre, or hallucinations consist of hearing one voice participating in a running commentary of the patient's actions or of hearing two or more voices conversing with each other, only that symptom is required above. The speech disorganization criterion is only met if it is severe enough to substantially impair communication.
  2. Social or occupational dysfunction: For a significant portion of the time since the onset of the disturbance, one or more major areas of functioning such as work, interpersonal relations, or self-care, are markedly below the level achieved prior to the onset.
  3. Significant duration: Continuous signs of the disturbance persist for at least six months. This six-month period must include at least one month of symptoms (or less, if symptoms remitted with treatment).


If signs of disturbance are present for more than a month but less than six months, the diagnosis of schizophreniform disorder
Schizophreniform disorder
Schizophreniform disorder is a mental disorder diagnosed when symptoms of schizophrenia are present for a significant portion of the time within a one-month period, but signs of disruption are not present for the full six months required for the diagnosis of schizophrenia.The symptoms of both...

 is applied. Psychotic symptoms lasting less than a month may be diagnosed as brief psychotic disorder
Brief psychotic disorder
Brief psychotic disorder is a period of psychosis whose duration is generally shorter, non re-occurring, and not better accounted for by another condition....

, and various conditions may be classed as psychotic disorder not otherwise specified. Schizophrenia cannot be diagnosed if symptoms of mood disorder
Mood disorder
Mood disorder is the term designating a group of diagnoses in the Diagnostic and Statistical Manual of Mental Disorders classification system where a disturbance in the person's mood is hypothesized to be the main underlying feature...

 are substantially present (although schizoaffective disorder
Schizoaffective disorder
Schizoaffective disorder is a psychiatric diagnosis that describes a mental disorder characterized by recurring episodes of elevated or depressed mood, or of simultaneously elevated and depressed mood, that alternate with, or occur together with, distortions in perception.Schizoaffective disorder...

 could be diagnosed), or if symptoms of pervasive developmental disorder
Pervasive developmental disorder
Pervasive developmental disorders is a diagnostic category refers to a group of disorders characterized by delays or impairments in communication, social behaviors, and cognitive development.Pervasive developmental disorders include Autism, Asperger's syndrome, Rett's syndrome, Childhood...

 are present unless prominent delusions or hallucinations are also present, or if the symptoms are the direct physiological result of a general medical condition or a substance, such as abuse of a drug or medication.

Subtypes

The DSM-IV-TR contains five sub-classifications of schizophrenia, although the developers of DSM-5
DSM-5
The next edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders , commonly called DSM-5 , is currently in consultation, planning and preparation...

 are recommending they be dropped from the new classification:
  • Paranoid type: Delusions or auditory hallucinations are present, but thought disorder, disorganized behavior, or affective flattening are not. Delusions are persecutory and/or grandiose, but in addition to these, other themes such as jealousy, religiosity, or somatization
    Somatization
    Somatization is currently defined as "a tendency to experience and communicate somatic distress in response to psychosocial stress and to seek medical help for it".This can be, but not always, related to a psychological condition:...

     may also be present. (DSM code 295.3/ICD code F20.0)
  • Disorganized type
    Disorganized schizophrenia
    Disorganized schizophrenia, also known as hebephrenia is a subtype of schizophrenia as defined in the Diagnostic and Statistical Manual of Mental Disorders, DSM-IV code 295.10....

    : Named hebephrenic schizophrenia in the ICD. Where thought disorder and flat affect are present together. (DSM code 295.1/ICD code F20.1)
  • Catatonic type
    Catatonia
    Catatonia is a state of neurogenic motor immobility, and behavioral abnormality manifested by stupor. It was first described in 1874: Die Katatonie oder das Spannungsirresein ....

    : The subject may be almost immobile or exhibit agitated, purposeless movement. Symptoms can include catatonic stupor and waxy flexibility
    Waxy flexibility
    Waxy flexibility is a psychomotor symptom of catatonic schizophrenia which leads to a decreased response to stimuli and a tendency to remain in an immobile posture....

    . (DSM code 295.2/ICD code F20.2)
  • Undifferentiated type: Psychotic symptoms are present but the criteria for paranoid, disorganized, or catatonic types have not been met. (DSM code 295.9/ICD code F20.3)
  • Residual type: Where positive symptoms are present at a low intensity only. (DSM code 295.6/ICD code F20.5)


The ICD-10 defines two additional subtypes:
  • Post-schizophrenic depression: A depressive episode arising in the aftermath of a schizophrenic illness where some low-level schizophrenic symptoms may still be present. (ICD code F20.4)
  • Simple schizophrenia: Insidious and progressive development of prominent negative symptoms with no history of psychotic episodes. (ICD code F20.6)

Differential

Psychotic symptoms may be present in several other mental disorders, including bipolar disorder
Bipolar disorder
Bipolar disorder or bipolar affective disorder, historically known as manic–depressive disorder, is a psychiatric diagnosis that describes a category of mood disorders defined by the presence of one or more episodes of abnormally elevated energy levels, cognition, and mood with or without one or...

, borderline personality disorder
Borderline personality disorder
Borderline personality disorder is a personality disorder described as a prolonged disturbance of personality function in a person , characterized by depth and variability of moods.The disorder typically involves unusual levels of instability in mood; black and white thinking, or splitting; the...

, drug intoxication and drug-induced psychosis
Substance-induced psychosis
Substance-induced psychosis is a form of substance-related disorder where psychosis can be attributed to substance use.Various psychoactive substances have been implicated in causing, exacerbating, and/or precipitating psychotic states and/or disorders in users...

. Delusions ("non-bizarre") are also present in delusional disorder
Delusional disorder
Delusional disorder is an uncommon psychiatric condition in which patients present with circumscribed symptoms of non-bizarre delusions, but with the absence of prominent hallucinations and no thought disorder, mood disorder, or significant flattening of affect...

, and social withdrawal in social anxiety disorder
Social anxiety disorder
Social anxiety disorder , also known as social phobia, is an anxiety disorder characterized by intense fear in social situations causing considerable distress and impaired ability to function in at least some parts of daily life...

, avoidant personality disorder
Avoidant personality disorder
Avoidant personality disorder is a personality disorder recognized in the Diagnostic and Statistical Manual of Mental Disorders handbook in a person characterized by a pervasive pattern of social inhibition, feelings of inadequacy, extreme sensitivity to negative evaluation, and avoidance of...

 and schizotypal personality disorder
Schizotypal personality disorder
Schizotypal personality disorder, or simply schizotypal disorder, is a personality disorder that is characterized by a need for social isolation, anxiety in social situations, odd behavior and thinking, and often unconventional beliefs.-Genetic:...

. Schizophrenia is comorbid with obsessive-compulsive disorder
Obsessive-compulsive disorder
Obsessive–compulsive disorder is an anxiety disorder characterized by intrusive thoughts that produce uneasiness, apprehension, fear, or worry, by repetitive behaviors aimed at reducing the associated anxiety, or by a combination of such obsessions and compulsions...

 (OCD) considerably more often than could be explained by pure chance, although it can be difficult to distinguish obsessions that occur in OCD from the delusions of schizophrenia.

A more general medical and neurological examination may be needed to rule out medical illnesses which may rarely produce psychotic schizophrenia-like symptoms, such as metabolic disturbance, systemic infection, syphilis
Syphilis
Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...

, HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

 infection, epilepsy
Epilepsy
Epilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...

, and brain lesions. It may be necessary to rule out a delirium
Delirium
Delirium or acute confusional state is a common and severe neuropsychiatric syndrome with core features of acute onset and fluctuating course, attentional deficits and generalized severe disorganization of behavior...

, which can be distinguished by visual hallucinations, acute onset and fluctuating level of consciousness, and indicates an underlying medical illness. Investigations are not generally repeated for relapse unless there is a specific medical indication or possible adverse effects from antipsychotic medication.

Prevention

Evidence for the effectiveness of early intervention is inconclusive. While there is some evidence that early intervention in those with a psychotic episode may improve short term outcomes, there is little benefit from these measures after five years. Attempting to prevent schizophrenia in the prodrome phase is of uncertain benefit and therefore as of 2009 is not recommended. Prevention is difficult as there are no reliable markers for the later development of the disease.

Management

The primary treatment of schizophrenia is antipsychotic medications, often in combination with psychological and social supports. Hospitalization may occur for severe episodes either voluntarily or (if mental health legislation allows it) involuntarily
Involuntary commitment
Involuntary commitment or civil commitment is a legal process through which an individual with symptoms of severe mental illness is court-ordered into treatment in a hospital or in the community ....

. Long-term hospitalization is uncommon since deinstitutionalization beginning in the 1950s, although still occurs. Community support services including drop-in centers, visits by members of a community mental health team
Community mental health service
Community mental health services , also known as Community Mental Health Teams in the United Kingdom, support or treat people with mental disorders in a domiciliary setting, instead of a psychiatric hospital . The array of community mental health services vary depending on the country in which...

, supported employment and support groups are common. Some evidence indicates that regular exercise has a positive effect on the physical and mental health of those with schizophrenia.

Medication

The first-line psychiatric treatment for schizophrenia is antipsychotic medication, which can reduce the positive symptoms of psychosis in about 7–14 days. Antipsychotics, however, fail to significantly ameliorate the negative symptoms and cognitive dysfunction.

The choice of which antipsychotic to use is based on benefits, risks, and costs. It is debatable whether, as a class, typical or atypical antipsychotics are better. Both have equal drop-out and symptom relapse rates when typicals are used at low to moderate dosages. There is a good response in 40–50%, a partial response in 30–40%, and treatment resistance (failure of symptoms to respond satisfactorily after six weeks to two of three different antipsychotics) in 20% of people. Clozapine
Clozapine
Clozapine is an antipsychotic medication used in the treatment of schizophrenia, and is also used off-label in the treatment of bipolar disorder. Wyatt. R and Chew...

 is an effective treatment for those who respond poorly to other drugs, but it has the potentially serious side effect of agranulocytosis
Agranulocytosis
Granulopenia, also known as Agranulosis or Agranulocytosis, is an acute condition involving a severe and dangerous leukopenia , most commonly of neutrophils causing a neutropenia in the circulating blood. It represents a severe lack of one major class of infection-fighting white blood cells...

 (lowered white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...

 count) in 1–4%.

With respect to side effects typical antipsychotics are associated with a higher rate of extrapyramidal side effects while atypicals are associated with considerable weight gain, diabetes and risk of metabolic syndrome
Metabolic syndrome
Metabolic syndrome is a combination of medical disorders that, when occurring together, increase the risk of developing cardiovascular disease and diabetes. It affects one in five people in the United States and prevalence increases with age...

. While atypicals have fewer extrapyramidal side effects these differences are modest. Some atypicals such as quetiapine
Quetiapine
Quetiapine , is an atypical antipsychotic approved for the treatment of schizophrenia, and bipolar disorder....

 and risperidone
Risperidone
Risperidone is a second generation or atypical antipsychotic, sold under the trade name . It is used to treat schizophrenia , schizoaffective disorder, the mixed and manic states associated with bipolar disorder, and irritability in people with autism...

 are associated with a higher risk of death compared to the atypical perphenazine
Perphenazine
Perphenazine is a typical antipsychotic drug. Chemically, it is classified as a piperazinyl phenothiazine. It has been in clinical use for decades....

, while clozapine is associated with the lowest risk of death. It remains unclear whether the newer antipsychotics reduce the chances of developing neuroleptic malignant syndrome
Neuroleptic malignant syndrome
Neuroleptic malignant syndrome is a life- threatening neurological disorder most often caused by an adverse reaction to neuroleptic or antipsychotic drugs...

, a rare but serious neurological disorder.

For people who are unwilling or unable to take medication regularly, long-acting depot preparations of antipsychotics may be used to achieve control. When used in combination with psychosocial interventions they may improve long-term adherence to treatment.

Psychosocial

A number of psychosocial interventions may be useful in the treatment of schizophrenia including: family therapy
Family therapy
Family therapy, also referred to as couple and family therapy, family systems therapy, and family counseling, is a branch of psychotherapy that works with families and couples in intimate relationships to nurture change and development. It tends to view change in terms of the systems of...

, assertive community treatment
Assertive Community Treatment
Assertive community treatment, or ACT, is an intensive and highly integrated approach for community mental health service delivery. ACT programs serve people whose symptoms of mental illness result in severe functional difficulties that interfere with their ability to achieve personally meaningful...

, supported employment, cognitive remediation
Cognitive Remediation Therapy
Cognitive Remediation Therapy is a cognitive rehabilitation therapy developed at King's College in London designed to improve neurocognitive abilities such as attention, working memory, cognitive flexibility and planning, and executive functioning which leads to improved social functioning.CRT...

, skills training, cognitive behavioral therapy (CBT), token economic interventions, and psychosocial interventions for substance use and weight management. Family therapy or education, which addresses the whole family system of an individual, may reduce relapses and hospitalizations. The evidence for CBT's effectiveness in either reducing symptoms or preventing relapse is minimal. Art or drama therapy have not been well-researched.

Prognosis

Schizophrenia has great human and economic costs. It results in a decreased life expectancy of 12–15 years, primarily because of its association with obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...

, sedentary lifestyles, and smoking
Smoking
Smoking is a practice in which a substance, most commonly tobacco or cannabis, is burned and the smoke is tasted or inhaled. This is primarily practised as a route of administration for recreational drug use, as combustion releases the active substances in drugs such as nicotine and makes them...

, with an increased rate of suicide
Suicide
Suicide is the act of intentionally causing one's own death. Suicide is often committed out of despair or attributed to some underlying mental disorder, such as depression, bipolar disorder, schizophrenia, alcoholism, or drug abuse...

 playing a lesser role. These differences in life expectancy increased between the 1970s and 1990s, and between the 1990s and first decade of the 21st century did not change substantially in a health system with open access to care (Finland).

Schizophrenia is a major cause of disability
Disability
A disability may be physical, cognitive, mental, sensory, emotional, developmental or some combination of these.Many people would rather be referred to as a person with a disability instead of handicapped...

, with active psychosis ranked as the third-most-disabling condition after quadriplegia
Quadriplegia
Tetraplegia, also known as quadriplegia, is paralysis caused by illness or injury to a human that results in the partial or total loss of use of all their limbs and torso; paraplegia is similar but does not affect the arms...

 and dementia
Dementia
Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...

 and ahead of paraplegia
Paraplegia
Paraplegia is an impairment in motor or sensory function of the lower extremities. The word comes from Ionic Greek: παραπληγίη "half-striking". It is usually the result of spinal cord injury or a congenital condition such as spina bifida that affects the neural elements of the spinal canal...

 and blindness
Blindness
Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...

. Approximately three-fourths of people with schizophrenia have ongoing disability with relapses. Some people do recover completely and others function well in society. Most people with schizophrenia live independently with community support. In people with a first episode of psychosis a good long-term outcome occurs in 42%, an intermediate outcome in 35% and a poor outcome in 27%. Outcomes for schizophrenia appear better in the developing than the developed world. These conclusions, however, have been questioned.

There is a higher than average suicide
Suicide
Suicide is the act of intentionally causing one's own death. Suicide is often committed out of despair or attributed to some underlying mental disorder, such as depression, bipolar disorder, schizophrenia, alcoholism, or drug abuse...

 rate associated with schizophrenia. This has been cited at 10%, but a more recent analysis of studies and statistics revises the estimate to 4.9%, most often occurring in the period following onset or first hospital admission. Several times more (20 to 40%) attempt suicide at least once. There are a variety of risk factors, including male gender, depression, and a high intelligence quotient
Intelligence quotient
An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean score within an age group is set to 100 and the standard deviation to 15...

.

Schizophrenia and smoking
Schizophrenia and smoking
Studies across 20 countries show a strong association between schizophrenia and smoking. For example, in the United States, 80% or more of schizophrenics smoke, compared to 20% of the general population in 2006....

 have shown a strong association in studies world-wide. Use of cigarettes is especially high in individuals diagnosed with schizophrenia, with estimates ranging from 80% to 90% being regular smokers, as compared to 20% of the general population. Those who smoke tend to smoke heavily, and additionally smoke cigarettes with high nicotine content.

Some evidence suggests that paranoid schizophrenia may have a better prospect than other types of schizophrenia for independent living and occupational functioning.

Epidemiology


Schizophrenia affects around 0.3–0.7% of people at some point in their life, or 24 million people worldwide as of 2011. It occurs 1.4 times more frequently in males than females and typically appears earlier in men—the peak ages of onset are 20–28 years for males and 26–32 years for females. Onset in childhood
Pediatric schizophrenia
Pediatric schizophrenia is a type of mental disorder that is characterized by degeneration of thinking, motor, and emotional processes in children and young adults under the age of 18...

 is much rarer, as is onset in middle- or old age. Despite the received wisdom that schizophrenia occurs at similar rates worldwide, its prevalence varies across the world, within countries, and at the local and neighborhood level. It causes approximately 1% of worldwide disability adjusted life years. The rate of schizophrenia varies up to threefold depending on how it is defined.

History

Accounts of a schizophrenia-like syndrome
Syndrome
In medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...

 are thought to be rare in the historical record before the 19th century, although reports of irrational, unintelligible, or uncontrolled behavior were common. A detailed case report in 1797 concerning James Tilly Matthews
James Tilly Matthews
James Tilly Matthews was a London tea broker, originally from Wales, who was committed to the Bethlem psychiatric hospital in 1797, and is considered to be the first fully documented case of paranoid schizophrenia....

, and accounts by Phillipe Pinel published in 1809, are often regarded as the earliest cases of the illness in the medical and psychiatric literature. Schizophrenia was first described as a distinct syndrome affecting teenagers and young adults by Bénédict Morel
Bénédict Morel
Bénédict Augustin Morel , was a French physician born in Vienna, Austria. He was an influential figure in the field of psychiatry during the mid-19th century....

 in 1853, termed démence précoce (literally 'early dementia'). The term dementia praecox
Dementia praecox
Dementia praecox refers to a chronic, deteriorating psychotic disorder characterized by rapid cognitive disintegration, usually beginning in the late teens or early adulthood. It is a term first used in 1891 in this Latin form by Arnold Pick , a professor of psychiatry at the German branch of...

 was used in 1891 by Arnold Pick
Arnold Pick
Arnold Pick was a Czech neurologist and psychiatrist. He is known for identifying the clinical syndrome of Pick's Disease and the Pick bodies that are characteristic of the disorder. He was the first to name reduplicative paramnesia. He was also to use the term dementia praecox .- External links...

 in a case report of a psychotic disorder. In 1893 Emil Kraepelin
Emil Kraepelin
Emil Kraepelin was a German psychiatrist. H.J. Eysenck's Encyclopedia of Psychology identifies him as the founder of modern scientific psychiatry, as well as of psychopharmacology and psychiatric genetics. Kraepelin believed the chief origin of psychiatric disease to be biological and genetic...

 introduced a broad new distinction in the classification of mental disorders
Classification of mental disorders
The classification of mental disorders, also known as psychiatric nosology or taxonomy, is a key aspect of psychiatry and other mental health professions and an important issue for consumers and providers of mental health services...

 between dementia praecox
Dementia praecox
Dementia praecox refers to a chronic, deteriorating psychotic disorder characterized by rapid cognitive disintegration, usually beginning in the late teens or early adulthood. It is a term first used in 1891 in this Latin form by Arnold Pick , a professor of psychiatry at the German branch of...

 and mood disorder (termed manic depression and including both unipolar and bipolar depression). Kraepelin believed that dementia praecox was primarily a disease of the brain, and particularly a form of dementia, distinguished from other forms of dementia such as Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...

 which typically occur later in life.

The word schizophrenia—which translates roughly as "splitting of the mind" and comes from the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 roots schizein (σχίζειν, "to split") and phrēn, phren- (φρήν, φρεν-, "mind")—was coined by Eugen Bleuler
Eugen Bleuler
Paul Eugen Bleuler was a Swiss psychiatrist most notable for his contributions to the understanding of mental illness and for coining the term "schizophrenia."-Biography:...

 in 1908 and was intended to describe the separation of function between personality
Personality psychology
Personality psychology is a branch of psychology that studies personality and individual differences. Its areas of focus include:* Constructing a coherent picture of the individual and his or her major psychological processes...

, thinking
Thought
"Thought" generally refers to any mental or intellectual activity involving an individual's subjective consciousness. It can refer either to the act of thinking or the resulting ideas or arrangements of ideas. Similar concepts include cognition, sentience, consciousness, and imagination...

, memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

, and perception
Perception
Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs...

. Bleuler described the main symptoms as 4 As: flattened Affect, Autism, impaired Association of ideas and Ambivalence. Bleuler realized that the illness was not a dementia, as some of his patients improved rather than deteriorated, and thus proposed the term schizophrenia instead. Treatment was revolutionized in the mid-1950s with the development and introduction of chlorpromazine
Chlorpromazine
Chlorpromazine is a typical antipsychotic...

.

In the early 1970s, the diagnostic criteria for schizophrenia was the subject of a number of controversies which eventually led to the operational criteria
Operational definition
An operational definition defines something in terms of the specific process or set of validation tests used to determine its presence and quantity. That is, one defines something in terms of the operations that count as measuring it. The term was coined by Percy Williams Bridgman and is a part of...

 used today. It became clear after the 1971 US-UK Diagnostic Study that schizophrenia was diagnosed to a far greater extent in America than in Europe. This was partly due to looser diagnostic criteria in the US, which used the DSM-II manual, contrasting with Europe and its ICD-9. David Rosenhan's
David Rosenhan
David L. Rosenhan is an American psychologist. He is best known for the Rosenhan experiment.Rosenhan received his Bachelor of Arts degree from Yeshiva University...

 1972 study, published in the journal Science
Science (journal)
Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....

 under the title "On being sane in insane places
Rosenhan experiment
The Rosenhan experiment was a famous experiment into the validity of psychiatric diagnosis conducted by psychologist David Rosenhan in 1973. It was published in the journal Science under the title "On being sane in insane places." The study is considered an important and influential criticism of...

", concluded that the diagnosis of schizophrenia in the US was often subjective and unreliable. These were some of the factors leading to the revision not only of the diagnosis of schizophrenia, but the revision of the whole DSM manual, resulting in the publication of the DSM-III in 1980.

The term schizophrenia is commonly misunderstood to mean that affected persons have a "split personality". Although some people diagnosed with schizophrenia may hear voices and may experience the voices as distinct personalities, schizophrenia does not involve a person changing among distinct multiple personalities. The confusion arises in part due to the literal interpretation of Bleuler's term schizophrenia. The first known misuse of the term to mean "split personality" was in an article by the poet T. S. Eliot
T. S. Eliot
Thomas Stearns "T. S." Eliot OM was a playwright, literary critic, and arguably the most important English-language poet of the 20th century. Although he was born an American he moved to the United Kingdom in 1914 and was naturalised as a British subject in 1927 at age 39.The poem that made his...

 in 1933.

Society and culture

Social stigma
Social stigma
Social stigma is the severe disapproval of or discontent with a person on the grounds of characteristics that distinguish them from other members of a society.Almost all stigma is based on a person differing from social or cultural norms...

 has been identified as a major obstacle in the recovery of patients with schizophrenia. In a large, representative sample from a 1999 study, 12.8% of Americans believed that individuals with schizophrenia were "very likely" to do something violent against others, and 48.1% said that they were "somewhat likely" to. Over 74% said that people with schizophrenia were either "not very able" or "not able at all" to make decisions concerning their treatment, and 70.2% said the same of money management decisions. The perception of individuals with psychosis as violent has more than doubled in prevalence since the 1950s, according to one meta-analysis.

In 2002 the term for schizophrenia in Japan was changed from Seishin-Bunretsu-Byō 精神分裂病 (mind-split-disease) to Tōgō-shitchō-shō 統合失調症 (integration disorder
Integration disorder
Tōgō-shitchō-shō or integration disorder is a Japanese psychiatric diagnosis that replaced the previous diagnostic category of Seishin Bunretsu Byo which was equivalent to the DSM-IV or ICD-10 diagnosis of schizophrenia....

) to reduce stigma. The new name was inspired by the biopsychosocial model; it increased the percentage of patients who were informed of the diagnosis from 37% to 70% over three years.

In the United States, the cost of schizophrenia—including direct costs (outpatient, inpatient, drugs, and long-term care) and non-health care costs (law enforcement, reduced workplace productivity, and unemployment)—was estimated to be $62.7 billion in 2002.

The book
A Beautiful Mind (book)
A Beautiful Mind is an unauthorized biography of Nobel Prize-winning economist and mathematician John Forbes Nash, Jr. by Sylvia Nasar, professor of journalism at Columbia University...

 and film
A Beautiful Mind (film)
A Beautiful Mind is a 2001 American drama film based on the life of John Nash, a Nobel Laureate in Economics. The film was directed by Ron Howard and written by Akiva Goldsman. It was inspired by a bestselling, Pulitzer Prize-nominated 1998 book of the same name by Sylvia Nasar...

 A Beautiful Mind chronicles the life of John Forbes Nash
John Forbes Nash
John Forbes Nash, Jr. is an American mathematician whose works in game theory, differential geometry, and partial differential equations have provided insight into the forces that govern chance and events inside complex systems in daily life...

, a Nobel Prize
Nobel Prize
The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. The will of the Swedish chemist Alfred Nobel, the inventor of dynamite, established the prizes in 1895...

-winning mathematician who was diagnosed with schizophrenia.

See also

  • Catastrophic schizophrenia
    Catastrophic schizophrenia
    In psychiatry, catastrophic schizophrenia or schizocaria is a rare and acute form of schizophrenia leading directly to a severe and unremitting chronic psychosis and deterioration of the personality...

  • Disorganized schizophrenia
    Disorganized schizophrenia
    Disorganized schizophrenia, also known as hebephrenia is a subtype of schizophrenia as defined in the Diagnostic and Statistical Manual of Mental Disorders, DSM-IV code 295.10....

  • Dopamine hypothesis of schizophrenia
    Dopamine hypothesis of schizophrenia
    The dopamine hypothesis of schizophrenia or the dopamine hypothesis of psychosis is a model attributing symptoms of schizophrenia to a disturbed and hyperactive dopaminergic signal transduction. The model draws evidence from the observation that a large number of antipsychotics have...

  • Evolution of schizophrenia
    Evolution of schizophrenia
    The evolution of schizophrenia has emerged as a by-product of the evolution of the human brain. Schizophrenia arose in all human populations about 5-7 millions years ago and is present in all human populations at about the same frequency of 1% . The evolution of the human brain that has led to this...

  • Glutamate hypothesis of schizophrenia
    Glutamate hypothesis of schizophrenia
    The glutamate hypothesis of schizophrenia models the subset of pathologic mechanisms linked to glutamatergic signaling. The hypothesis was initially based on a set of clinical, neuropathological, and, later, genetic findings pointing at a hypofunction of glutamatergic signaling via NMDA receptors...

  • Interpretation of Schizophrenia
  • On the Origin of the "Influencing Machine" in Schizophrenia
  • Pediatric schizophrenia
    Pediatric schizophrenia
    Pediatric schizophrenia is a type of mental disorder that is characterized by degeneration of thinking, motor, and emotional processes in children and young adults under the age of 18...

  • Physical health in schizophrenia
    Physical health in schizophrenia
    People with schizophrenia are at higher than average risk of physical ill health and die earlier than the general population from natural causes. The fatal conditions include cardiovascular, respiratory and metabolic disorders....

  • Pseudoneurotic schizophrenia
    Pseudoneurotic schizophrenia
    Pseudoneurotic schizophrenia is defined by Stedman's Medical Dictionary as "schizophrenia in which the underlying psychotic process is masked by complaints ordinarily regarded as neurotic." A person is diagnosed with borderline schizophrenia when they exhibit one or another of non-psychotic...

  • Schedule for Affective Disorders and Schizophrenia
    Schedule for Affective Disorders and Schizophrenia
    The Schedule for Affective Disorders and Schizophrenia is a collection of psychiatric diagnostic criteria and symptom rating scales published in 1978. There are three versions of the schedule, the regular SADS, the lifetime version and a version for measuring change in symptomology...

  • Schizophrenia and smoking
    Schizophrenia and smoking
    Studies across 20 countries show a strong association between schizophrenia and smoking. For example, in the United States, 80% or more of schizophrenics smoke, compared to 20% of the general population in 2006....

  • Schizophrenia and the Effects of Estrogen on Schizophrenia
    Schizophrenia and the Effects of Estrogen on Schizophrenia
    -Age of Onset:Gender differences have been observed in the age of onset of schizophrenia. Women have a later age of onset and on average they are diagnosed 2 to 10 years later than men. In fact, the first onset of schizophrenia for men occurs around the ages of 20 to 25, while in women the first...

  • Schizophrenia Bulletin
    Schizophrenia Bulletin
    Schizophrenia Bulletin is a peer-reviewed medical journal which covers research relating to the etiology and treatment of schizophrenia. The journal is published bimonthly by Oxford University Press in association with the Maryland Psychiatric Research Center and Schizophrenia International...

  • Schizophrenia Fellowship of NSW
  • Schizophrenia International Research Society
    Schizophrenia International Research Society
    The Schizophrenia International Research Society is an academic organization with a global scope, devoted to the study of schizophrenia and related disorders.- External links :* *...

  • Schizophrenia Research
    Schizophrenia Research
    Schizophrenia Research is the official, peer reviewed scientific journal of the Schizophrenia International Research Society and publishes articles of original research, systematic reviews etc. relating to the biology and treatment of schizophrenia. The journal's 2010 impact factor is 4.374....

  • Schizophrenia Research Forum
    Schizophrenia Research Forum
    Schizophrenia Research Forum is a website dedicated to convey information about schizophrenia.It hosts the SzGene Database, which provides a comprehensive, unbiased and regularly updated field synopsis of genetic association studies performed in schizophrenia with hundreds of up-to-date...

  • Schizophrenia Society of Ontario
    Schizophrenia Society of Ontario
    The Schizophrenia Society of Ontario is a charitable organization located in Ontario, Canada that exists to help those affected by schizophrenia....

  • Sluggishly progressing schizophrenia
    Sluggishly progressing schizophrenia
    Sluggishly progressing schizophrenia or sluggish schizophrenia was a category of schizophrenia diagnosed by psychiatrists in the Soviet Union...

  • Social construction of schizophrenia
    Social construction of schizophrenia
    Social Constructionism, a branch of sociology, queries commonly held views on the nature of reality touching on themes of normality and abnormality within the context of power and oppression in societal structures....

  • The Protest Psychosis: How Schizophrenia Became a Black Disease
    The Protest Psychosis: How Schizophrenia Became a Black Disease
    The Protest Psychosis: How Schizophrenia Became a Black Disease is 2010 book written by psychiatrist Jonathan Metzl , and published by Beacon Press, covering the history of the 1960s Ionia State Hospital—located in Ionia, Michigan and now converted to a prison...

  • The Schizophrenia of Modern Ethical Theories
    The Schizophrenia of Modern Ethical Theories
    right|250px|Illustration of moral schizophreniaThe Schizophrenia of Modern Ethical Theories is a popular paper in ethics by Michael Stocker. The central claim of the paper is that some modern ethical theories fail to account for motive in their theories, producing a sort of schizophrenia because...


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