Causes of psychiatric disorder
Encyclopedia
The causes of mental disorders are complex, and interact and vary according to the particular disorder and individual. Genetics, early development, drugs, a loss of a family member, disease or injury, neurocognitive and psychological mechanisms, and life experiences, society and culture, can all contribute to the development or progression of different mental disorders.

General theories

There are a number of theories or models
Scientific modelling
Scientific modelling is the process of generating abstract, conceptual, graphical and/or mathematical models. Science offers a growing collection of methods, techniques and theory about all kinds of specialized scientific modelling...

 seeking to explain the causes (etiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....

) of mental disorder
Disorder
Disorder may refer to :* Chaos, unpredictability and in the metaphysical sense, it is the opposite of law and order* Civil disorder, one or more forms of disturbance caused by a group of people...

s. They may be based on different foundations, including their basic 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...

.

The most common view is that disorders tend to result from genetic vulnerabilities and environmental stressors combining to cause patterns of dysfunction or trigger disorders (Diathesis-stress model
Diathesis-stress model
The diathesis–stress model is a psychological theory that explains behavior as a result of both biological and genetic vulnerability , and stress from life experiences....

). A practical mixture of models may often be used to explain particular issues and disorders, although there may be difficulty defining boundaries for indistinct psychiatric syndromes.

The primary model of contemporary mainstream Western psychiatry is the biopsychosocial model
Biopsychosocial model
The biopsychosocial model is a general model or approach that posits that biological, psychological , and social factors, all play a significant role in human functioning in the context of disease or illness...

 (BPS), which merges together biological, psychological and social factors. It may be commonly neglected or misapplied in practice due to being too broad or relativistic, however, and biopsychiatry has tended to follow a biomedical model focused on organic or "hardware" pathology of the brain.

Psychoanalytic theories, focused on unresolved internal and relational conflicts, have been posited as overall explanations of mental disorder, although today most psychoanalytic groups are said to adhere to the biopsychosocial model and to accept an eclectic mix of subtypes of psychoanalysis.

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...

 (or more specifically evolutionary psychopathology or psychiatry) has also been proposed as an overall theory, positing that many mental disorders involve the dysfunctional operation of mental modules adapted to ancestral physical or social environments but not necessarily to modern ones. Attachment theory
Attachment theory
Attachment theory describes the dynamics of long-term relationships between humans. Its most important tenet is that an infant needs to develop a relationship with at least one primary caregiver for social and emotional development to occur normally. Attachment theory is an interdisciplinary study...

 is another kind of evolutionary-psychological approach sometimes applied in the context for mental disorders, which focuses on the role of early caregiver-child relationships, responses to danger, and the search for a satisfying reproductive relationship in adulthood.

An overall distinction is also commonly made between a "medical model" (also known as a biomedical or disease model), and a "social model" (also known as an empowerment or recovery model) of mental disorder and 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 the former focusing on hypothesized disease processes and symptoms, and the latter focusing on hypothesized social constructionism
Social constructionism
Social constructionism and social constructivism are sociological theories of knowledge that consider how social phenomena or objects of consciousness develop in social contexts. A social construction is a concept or practice that is the construct of a particular group...

 and social contexts.

Genes

Family-linkage and twin studies have indicated that genetic factors often play an important role in the development of mental disorders. The reliable identification of specific genetic susceptibility to particular disorders, through linkage
Genetic linkage
Genetic linkage is the tendency of certain loci or alleles to be inherited together. Genetic loci that are physically close to one another on the same chromosome tend to stay together during meiosis, and are thus genetically linked.-Background:...

 or association studies
Genetic association
Genetic association is the occurrence, more often than can be readily explained by chance, of two or more traits in a population of individuals, of which at least one trait is known to be genetic....

, has proven difficult. This has been reported to be likely due to the complexity of interactions between genes, environmental events, and early development or to the need for new research strategies. The 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...

 of behavioral traits associated with mental disorder may be greater in permissive than in restrictive environments, and susceptibility genes probably work through both "within-the-skin" (physiological) pathways and "outside-the-skin" (behavioral and social) pathways. Investigations increasingly focus on links between genes and endophenotypes—more specific traits (including neurophysiological, biochemical, endocrinological, neuroanatomical, cognitive, or neuropsychological)—rather than disease categories. With regard to a prominent mental disorder, Schizophrenia, genetics have been shown to have an increasingly complicated role in the disease. For a long time consensus among scientists was that certain alleles were responsible for schizophrenia, but recent research has shown that this is not necessarily the case. In a study done in 2008 by Walsh et al., the genetics of schizophrenics were compared to those of non-affected individuals. The group did micro-arrays of each individuals' genome looking for structural variants greater than 100kbp. Individuals with schizophrenia were three times as likely to harbor structural variants that duplicated or deleted one or more genes. This was even more prevalent in children as schizophrenics under age 18 were four times as likely to harbor these mutations. More importantly 53 previously unreported microduplications/deletions were discovered and virtually every rare structural mutation was different .

Pregnancy and birth

Environmental events surrounding pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

 and birth
Birth
Birth is the act or process of bearing or bringing forth offspring. The offspring is brought forth from the mother. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world...

 have been linked to an increased development of mental illness in the offspring
Offspring
In biology, offspring is the product of reproduction, of a new organism produced by one or more parents.Collective offspring may be known as a brood or progeny in a more general way...

. This includes maternal exposure to serious psychological stress
Stress (medicine)
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...

 or trauma
Psychological trauma
Psychological trauma is a type of damage to the psyche that occurs as a result of a traumatic event...

, conditions of famine, obstetric birth complications, infections, and gestational exposure to alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

 or 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...

. Such factors have been hypothesized to affect specific areas of neurodevelopment within the general developmental context and to restrict neuroplasticity
Neuroplasticity
Neuroplasticity is a non-specific neuroscience term referring to the ability of the brain and nervous system in all species to change structurally and functionally as a result of input from the environment. Plasticity occurs on a variety of levels, ranging from cellular changes involved in...

.

Additionally, pregnancy greatly increases the stress in typical women. Carrying an extra life within, women often stress over all the unnecessary events. Doctors have no way of knowing how much stress is too much, or too little. Studies had shown that the mother's excessive stress is extremely unhealthy for the mother and the child(ren) within as it greatly increases the chances of premature labour, which in turns, create more stress on the mother. Therefore, aside from damages to the child, pregnancy can also create great stress and can possibly lead to various mental disorders in mothers.

People with developmental disabilities, such as mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...

, are more likely to experience mental illness than those in the general community.

Disease, injury and infection

Higher rates of mood, psychotic, and substance abuse disorders have been found following traumatic brain injury
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...

 (TBI). Findings on the relationship between TBI severity and prevalence of subsequent psychiatric disorders have been inconsistent, and occurrence has been linked to prior mental health problems as well as direct neurophysiological effects, in a complex interaction with personality and attitude and social influences.

A number of psychiatric disorders have often been tentatively linked with microbial pathogens, particularly viruses; however while there have been some suggestions of links from animal studies, and some inconsistent evidence for infectious and immune mechanisms (including prenatally) in some human disorders, infectious disease models in psychiatry are reported to have not yet shown significant promise except in isolated cases. There have been some inconsistent findings of links between infection by the parasite Toxoplasma gondii
Toxoplasma gondii
Toxoplasma gondii is a species of parasitic protozoa in the genus Toxoplasma. The definitive host of T. gondii is the cat, but the parasite can be carried by many warm-blooded animals . Toxoplasmosis, the disease of which T...

 and human mental disorders such as schizophrenia, with the direction of causality unclear. A number of diseases of the white matter can cause symptoms of mental disorder.

Poorer general health has been found among individuals with severe mental illnesses, thought to be due to direct and indirect factors including diet, bacterial infections, substance use, exercise levels, effects of medications, socioeconomic disadvantages, lowered help-seeking or treatment adherence, or poorer healthcare provision. Some chronic general medical conditions have been linked to some aspects of mental disorder, such as AIDS
AIDS
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...

-related psychosis.

The current research on Lyme's disease caused by a deer tick, and related toxins, is expanding the link between bacterial infections and mental illness.

Individual characteristics

Mental characteristics of individuals, as assessed by both neurological and psychological studies, have been linked to the development and maintenance of mental disorders. This includes cognitive or neurocognitive
Neurocognitive
Neurocognitive is a term used to describe cognitive functions closely linked to the function of particular areas, neural pathways, or cortical networks in the brain substrate layers of neurological matrix at the cellular molecular level...

 factors, such as the way a person perceives, thinks or feels about certain things; or an individual's overall personality, temperament or coping style or the extent of protective factors or "positive illusions" such as optimism, personal control and a sense of meaning.

Abnormal levels of 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...

 activity have been implicated in a number of disorders (e.g., reduced in ADHD, increased in schizophrenia), thought to be part of the complex encoding of the importance of events in the external world. Dysfunction in 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...

 and other monoamine neurotransmitters such as norepinephrine
Norepinephrine
Norepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...

 and 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...

 has also been centrally implicated in mental disorders, including major depression as well as obsessive compulsive disorder, phobias, posttraumatic stress disorder, and generalized anxiety disorder, although the limitations of a simple "monoamine hypothesis" have been highlighted and studies of depleted levels of monoamine neurotransmitters have tended to indicate no simple or directly causal relation with mood or major depression, although features of these pathways may form trait vulnerabilities to depression. Dysfunction of the central gamma-aminobutyric (GABA
Gabâ
Gabâ or gabaa, for the people in many parts of the Philippines), is the concept of a non-human and non-divine, imminent retribution. A sort of negative karma, it is generally seen as an evil effect on a person because of their wrongdoings or transgressions...

) system following stress has also been associated with anxiety spectrum disorders and there is now a body of clinical and preclinical literature also indicating an overlapping role in mood disorder.

Findings have indicated abnormal functioning of brainstem structures in disorders such as schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...

, related to impairments in maintaining sustained attention. Some abnormalities in the average size or shape of some regions of the brain have been found in some disorders, reflecting genes and/or experience. Studies of schizophrenia have tended to find enlarged ventricles
Ventricular system
The ventricular system is a set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal of the spinal cord.-Components:The system comprises four ventricles:* right and left lateral ventricles* third ventricle...

 and sometimes reduced volume of the cerebrum and 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...

, while studies of (psychotic) 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...

 have sometimes found increased amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...

 volume. Findings differ over whether volumetric abnormalities are risk factors or are only found alongside the course of mental health problems, possibly reflecting neurocognitive or emotional stress processes and/or medication use or substance use. Some studies have also found reduced hippocampal volumes in major depression, possibly worsening with time depressed.

Life events, emotional stress and relationships

It is reported that there is good evidence on the importance of psychosocial influences on psychopathology in general, although less known about the specific risk and protective mechanisms. Maltreatment in childhood and in adulthood, including sexual abuse
Sexual abuse
Sexual abuse, also referred to as molestation, is the forcing of undesired sexual behavior by one person upon another. When that force is immediate, of short duration, or infrequent, it is called sexual assault. The offender is referred to as a sexual abuser or molester...

, physical abuse
Physical abuse
Physical abuse is abuse involving contact intended to cause feelings of intimidation, injury, or other physical suffering or bodily harm.-Forms of physical abuse:*Striking*Punching*Belting*Pushing, pulling*Slapping*Whipping*Striking with an object...

, emotional abuse, domestic violence
Domestic violence
Domestic violence, also known as domestic abuse, spousal abuse, battering, family violence, and intimate partner violence , is broadly defined as a pattern of abusive behaviors by one or both partners in an intimate relationship such as marriage, dating, family, or cohabitation...

 and bullying, has been linked to the development of mental disorders, through a complex interaction of societal, family, psychological and biological factors. Negative or stressful life events more generally have been implicated in the development of a range of disorders, including mood and anxiety disorders. The main risks appear to be from a cumulative combination of such experiences over time, although exposure to a single major trauma can sometimes lead to psychopathology, including PTSD. Resilience
Psychological resilience
Resilience in psychology refers to the idea of an individual's tendency to cope with stress and adversity. This coping may result in the individual “bouncing back” to a previous state of normal functioning, or using the experience of exposure to adversity to produce a “steeling effect” and function...

 to such experiences varies, and a person may be resistant to some forms of experience but susceptible to others. Features associated with variations in resilience include genetic vulnerability, temperamental characteristics, cognitive set, coping patterns, and other experiences.

Relationship issues have been consistently linked to the development of mental disorders, with continuing debate on the relative importance of the home environment or work/school and peer group. Issues with parenting skills or parental depression or other problems may be a risk factor. Parental divorce appears to increase risk, perhaps only if there is family discord or disorganization, although a warm supportive relationship with one parent may compensate. Details of infant feeding, weaning, toilet training etc. do not appear to be importantly linked to psychopathology. Early social privation, or lack of ongoing, harmonious, secure, committed relationships, have been implicated in the development of mental disorders.

Some approaches, such as certain theories of co-counseling, may see all non-neurological mental disorders as the result of the self-regulating mechanisms of the mind (which accompany the physical expression of emotions) not being allowed to operate.

Neighborhoods, society and culture

Problems in communities or cultures, including poverty, unemployment or underemployment
Underemployment
Underemployment refers to an employment situation that is insufficient in some important way for the worker, relative to a standard. Examples include holding a part-time job despite desiring full-time work, and overqualification, where the employee has education, experience, or skills beyond the...

, lack of social cohesion, and migration, have been implicated in the development of mental disorders. Stresses and strains related to socioeconomic position (socioeconomic status
Socioeconomics
Socioeconomics or socio-economics or social economics is an umbrella term with different usages. 'Social economics' may refer broadly to the "use of economics in the study of society." More narrowly, contemporary practice considers behavioral interactions of individuals and groups through social...

 (SES) or social class
Social class
Social classes are economic or cultural arrangements of groups in society. Class is an essential object of analysis for sociologists, political scientists, economists, anthropologists and social historians. In the social sciences, social class is often discussed in terms of 'social stratification'...

) have been linked to the occurrence of major mental disorders, with a lower or more insecure educational, occupational, economic or social position generally linked to more mental disorders. There have been mixed findings on the nature of the links and on the extent to which pre-existing personal characteristics influence the links. Both personal resources and community factors have been implicated, as well as interactions between individual-level and regional-level income levels. The causal role of different socioeconomic factors may vary by country. Socioeconomic deprivation in neighborhoods can cause worse mental health, even after accounting for genetic factors. In addition, minority ethnic groups, including first or second-generation immigrants, have been found to be at greater risk for developing mental disorders, which has been attributed to various kinds of life insecurities and disadvantages, including racism
Racism
Racism is the belief that inherent different traits in human racial groups justify discrimination. In the modern English language, the term "racism" is used predominantly as a pejorative epithet. It is applied especially to the practice or advocacy of racial discrimination of a pernicious nature...

. The direction of causality is sometimes unclear, and alternative hypotheses such as the Drift Hypothesis
Drift Hypothesis
Drift hypothesis, concerning the relationship between mental illness and social class, is the argument that illness causes one to have a downward shift in social class. The circumstances of one's social class do not cause the onset of a mental disorder, but rather, an individual's deteriorating...

 sometimes need to be discounted.

Mental disorders have also been linked to the overarching social, economic and cultural system. A value system that promotes individualism, weakens social ties, and creates ambivalence towards children, is being spread or imposed via globalization
Globalization
Globalization refers to the increasingly global relationships of culture, people and economic activity. Most often, it refers to economics: the global distribution of the production of goods and services, through reduction of barriers to international trade such as tariffs, export fees, and import...

, yet could adversely affect children's mental health.
Due to the lack of knowledge that ordinary individuals have about mental health issues, many individuals who suffer from mental illness, especially children and adolescences are reluctant to express. Limited help and support coming from society and community combined with individuals' silences lead them to deteriorated conditions.
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