Long-term effects of cannabis - AbsoluteAstronomy.com

Though the long-term effects of cannabis have been studied, there remains much to be concluded. Because use of cannabis ranges widely from users who try it once, to people using it frequently in a year, as well as users who use it daily, it is hard to measure the health effects it has on the human body. Aside from the possible elevated risk of cancer due to smoking, many other studies have looked into the possibility that cannabis use can trigger other illnesses such as heart disease

Heart disease

Heart disease, cardiac disease or cardiopathy is an umbrella term for a variety of diseases affecting the heart. , it is the leading cause of death in the United States, England, Canada and Wales, accounting for 25.4% of the total deaths in the United States.-Types:-Coronary heart disease:Coronary...

, bi-polar disorder, depression

Depression (mood)

Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...

, mood swings

Mood Swings

Mood Swings is an album by Koby Israelite released in 2005 on Tzadik.- Track listing :# "Dror Ikra" - 3:03# "Return of the Idiots" - 2:19# "It Is Not a War Here" - 7:05# "Ethnometalogy" - 5:08# "Europa?" - 2:49# "Hiriya On My Mind" - 4:53...

or 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...

.

More research is no guarantee of greater consensus in the field of cannabis studies, however: both advocates and opponents of the drug are able to call upon multiple scientific studies supporting their respective positions. For instance, while cannabis has been correlated with the development of various mental disorders

Mental illness

A mental disorder or mental illness is a psychological or behavioral pattern generally associated with subjective distress or disability that occurs in an individual, and which is not a part of normal development or culture. Such a disorder may consist of a combination of affective, behavioural,...

in multiple studies, these studies differ widely as to whether cannabis use is the cause of the mental problems, whether the mental problems encourage cannabis use, or whether both the cannabis use and the mental problems are the effects of some other cause.

Reproductive and endocrine effects

It has been shown that administration of high doses of THC to animals lowers serum testosterone

Testosterone

Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

levels, impairs sperm

Spermatozoon

A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...

production, motility, and viability, disrupts the ovulation

Ovulation

Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...

cycle, and decreases output of gonadotropic hormones

Gonadotrope

Gonadotropes are endocrine cells in the anterior pituitary that produce the gonadotropins, follicle-stimulating hormone and luteinizing hormone...

. According to the 1997 Merck Manual of Diagnosis and Therapy
Merck Manual of Diagnosis and Therapy
The Merck Manual of Diagnosis and Therapy, often called simply The Merck Manual, is the world's best-selling medical textbook. First published in 1899, it is now in its 19th edition.-Professional Edition:...

, fertility effects related to cannabis use are uncertain.

Research has demonstrated that human sperm

Sperm

The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...

contains receptors which are stimulated by substances like THC and other cannabis-related chemicals. Tests have implied that smoking of marijuana could impact the sperm's functions, though this impact is unknown. There is some evidence that cannabis may compromise female fertility with a modest association reported between cannabis use and infertility in Mueller et al.'s case controlled study of 150 women with primary anovulatory infertility. While Wenger et al. indicate evidence that THC and anandamide

Anandamide

Anandamide, also known as N-arachidonoylethanolamide or AEA, is an endogenous cannabinoid neurotransmitter. The name is taken from the Sanskrit word ananda, which means "bliss, delight", and amide. It is synthesized from N-arachidonoyl phosphatidylethanolamine by multiple pathways...

increase the duration of pregnancy and increase the frequency of stillbirth in rats. In a report prepared for the Australian National Council on Drugs, Copeland, Gerber and Swift conclude that current understanding suggests cannabis-related substances are contraindicated in pregnancy, as are compounds that interact with endocannabinoid synthesis and metabolism.

Higher rates of testicular cancer in western nations have been linked to use of cannabis. A study conducted by the Fred Hutchinson Cancer Research Center

Fred Hutchinson Cancer Research Center

The Fred Hutchinson Cancer Research Center, is one of the world’s leading cancer research institutes...

and funded by the National Institutes of Health

National Institutes of Health

The National Institutes of Health are an agency of the United States Department of Health and Human Services and are the primary agency of the United States government responsible for biomedical and health-related research. Its science and engineering counterpart is the National Science Foundation...

, published in the journal Cancer
Cancer (journal)
Cancer is a peer-reviewed academic journal published by John Wiley & Sons for the American Cancer Society as their official journal. The journal started publication in 1948. Since 1997 one volume per year has the section title Cancer Cytopathology, with volume numbers integrated into those of...

March 15, 2009, linked long-term use of cannabis to an increased risk of 70 percent for testicular cancer

Testicular cancer

Testicular cancer is cancer that develops in the testicles, a part of the male reproductive system.In the United States, between 7,500 and 8,000 diagnoses of testicular cancer are made each year. In the UK, approximately 2,000 men are diagnosed each year. Over his lifetime, a man's risk of...

with the scientists concluding that cannabis is harmful to the human endocrine and reproductive system.

Pregnancy

A 1989 study of 1226 mothers published in the New England Journal of Medicine
New England Journal of Medicine
The New England Journal of Medicine is an English-language peer-reviewed medical journal published by the Massachusetts Medical Society. It describes itself as the oldest continuously published medical journal in the world.-History:...

concluded that "the use of marijuana or cocaine during pregnancy is associated with impaired fetal growth". Compared to fetal alcohol syndrome

Fetal alcohol syndrome

Fetal alcohol syndrome is a pattern of mental and physical defects that can develop in a fetus in association with high levels of alcohol consumption during pregnancy. Current research also implicates other lifestyle choices made by the prospective mother...

, similar types of facial features and related symptoms are not associated with prenatal marijuana exposure. THC passes into the breast milk

Breast milk

Breast milk, more specifically human milk, is the milk produced by the breasts of a human female for her infant offspring...

and might affect a breastfed infant

Infant

A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...

. Many studies about drug use during pregnancy are self-administered by the applicants and not always anonymous

Anonymity

Anonymity is derived from the Greek word ἀνωνυμία, anonymia, meaning "without a name" or "namelessness". In colloquial use, anonymity typically refers to the state of an individual's personal identity, or personally identifiable information, being publicly unknown.There are many reasons why a...

. The 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...

of using illicit drugs while pregnant discourages honest reporting and can invalidate the results. Studies show that women who consume cannabis while they are pregnant may also be likely to consume alcohol

Ethanol

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

, tobacco

Tobacco

Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...

, caffeine

Caffeine

Caffeine is a bitter, white crystalline xanthine alkaloid that acts as a stimulant drug. Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants...

, or other illicit drugs, which makes it difficult to deduce scientific facts about just marijuana use from statistical results. Very few large, well-controlled epidemiological

Epidemiology

Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

studies have taken place to understand the connection of marijuana use and pregnancy.

A study of the development of 59 Jamaica

Jamaica

Jamaica is an island nation of the Greater Antilles, in length, up to in width and 10,990 square kilometres in area. It is situated in the Caribbean Sea, about south of Cuba, and west of Hispaniola, the island harbouring the nation-states Haiti and the Dominican Republic...

n children was conducted with the children being monitored from childbirth to age 5 years. One-half of the sample's mothers used marijuana during pregnancy; they were paired with non-using mothers who matched age, parity, and socioeconomic status. Testing was done at 1, 3, and 30 days of age with the Brazelton Neonatal Behavioral Assessment Scale

Neonatal Behavioral Assessment Scale

The Neonatal Behavioral Assessment Scale was developed in 1973 by Dr. T. Berry Brazelton and his colleagues. It evaluates a wide range of 38 behaviors to build a behavioral profile of an infant up to 2 months old. This approach was innovative for recognizing that a baby is a highly-developed...

s, and at ages 4 and 5 years with the McCarthy Scales of Children's Abilities test. Data was also collected from the child's home environment and temperament, as well as standardized tests. The results over the entire research period showed no significant differences in development testing outcomes between using and non-using mothers. At 30 days of age, however, the children of marijuana-using mothers had higher scores on autonomic stability and reflexes. The absence of any differences between the exposed and non-exposed groups in the early neonatal period suggest that the better scores of exposed neonates at 1 month are traceable to the cultural positioning and social and economic characteristics of mothers using marijuana that select for the use of marijuana but also promote neonatal development.
Some studies have found that children of tobacco and marijuana-smoking mothers more frequently suffer from permanent cognitive deficits, concentration disorders, hyperactivity, and impaired social interactions than non-exposed children of the same age and social background. A recent study, with participation of scientists from Europe and the United States, has now identified that naturally occurring

Endogenous

Endogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...

endocannabinoid molecules play a role in establishing how certain nerve cells connect to each other in the fetal brain. Another study examining cannabinoid receptor proteins (CBRs) expressed in brain cells of mice determined that endogenous endocannabinoids assist in directing brain cell

Brain Cell

Brain Cell is a mail art project begun by Ryosuke Cohen in June 1985. The project is basically a networked art project where individual artists create their own 30x42cm work of art with stamps, drawings, stickers and so forth. This is sent to Cohen, who prints each cell - 150 copies each - with a...

directional development while in the womb. The researchers suggest that elevated blood THC levels due to cannabis consumption would affect brain development of human fetuses. In contrast, other studies in Jamaica have suggested that cannabis use by expectant mothers does not appear to cause birth defects or developmental delays in their newborn children.

Cannabis dependency

Despite cannabis being the most widely used illicit drug in the Western world, controlled trials for cannabis use disorder have only been reported in literature in the last 15 years. Research has shown a substantial percentage of cannabis users develop cannabis-related problems, including dependency. It should be noted that the dependency in question, in regards to cannabis, is "psychological dependency" rather than physical dependency. Most evidence has shown that cannabis poses no risk of physical dependency, as is the case with other drugs, like alcohol. Overall, the addiction potential for cannabis is significantly less than that for tobacco, alcohol, cocaine or heroin, but slightly higher than that for psilocybin

Psilocybin

Psilocybin is a naturally occurring psychedelic prodrug, with mind-altering effects similar to those of LSD and mescaline, after it is converted to psilocin. The effects can include altered thinking processes, perceptual distortions, an altered sense of time, and spiritual experiences, as well as...

, mescaline

Mescaline

Mescaline or 3,4,5-trimethoxyphenethylamine is a naturally occurring psychedelic alkaloid of the phenethylamine class used mainly as an entheogen....

, or LSD

LSD

Lysergic acid diethylamide, abbreviated LSD or LSD-25, also known as lysergide and colloquially as acid, is a semisynthetic psychedelic drug of the ergoline family, well known for its psychological effects which can include altered thinking processes, closed and open eye visuals, synaesthesia, an...

Withdrawal

At one time cannabis was considered a drug that had no withdrawal symptoms because users did not display symptoms similar to those withdrawing from alcohol or opiates. Contrary to this, experimental research supports reports of users who relate evidence of heavy cannabis use producing psychological and physical withdrawal symptoms. People who were before suffering cannabis addiction reported withdrawal from the drug. Common symptoms include trouble sleeping, sweating, fatigue, mood swings, cravings, anger, insomnia, depression and restlessness.

Mental health

Cannabis use has been assessed by several studies to be correlated with the development

Dual diagnosis

The term dual diagnosis is used to describe the comorbid condition of a person considered to be suffering from a mental illness and a substance abuse problem. There is considerable debate surrounding the appropriateness of the term being used to describe a heterogeneous group of individuals with...

of anxiety, psychosis, and depression. Studies have also shown a large correlation between tobacco cigarette smoking and such brain disorders, but there is not much said about cause and effect. Some studies regarding cannabis assess that the causality is more likely to involve a path from cannabis use to psychotic symptoms rather than a path from psychotic symptoms to cannabis use, while others assess the opposite direction of the causality, or hold cannabis to only form parts of the "causal constellation", while not inflicting mental health problems that would have occurred in the absence of the cannabis use. A common interpretation of the correlation and theorized direction of the causality is the self-medication hypothesis, which is based on partially or fully attributing the correlation between psychiatric diseases and cannabis to the extensive substance abuse among sufferers of certain mental disorders, before diagnosis in many cases, which increases the likeliness of cannabis use among the mentally ill and the undiagnosed, thus accounting for correlation and debunking some claims of causality with the opposite direction. As much as 60% of the mentally ill are suspected to be substance abusers, and many seem to prefer cannabis and alcohol.
Dr Stanley Zammit of Bristol and Cardiff universities (in the Daily Express newspaper of 27 July 2007) reported, "Even if cannabis did increase the risk of psychosis, most people using the drug would not get ill" But he added: "Nevertheless, we would still advise people to avoid or limit their use of this drug, especially if they start to develop any mental health symptoms or if they have relatives with psychotic illnesses." A 2007 study of studies published in the Lancet concluded that cannabis users are 40% more likely to be sufferers of a psychotic illness than non-users.

The BEACH study (Bettering the Evaluation and Care of Health) conducted by the Australian General Practice Statistics and Classification Centre, based at the University of Sydney

University of Sydney

The University of Sydney is a public university located in Sydney, New South Wales. The main campus spreads across the suburbs of Camperdown and Darlington on the southwestern outskirts of the Sydney CBD. Founded in 1850, it is the oldest university in Australia and Oceania...

, found that "cannabis smokers are more likely to suffer depression, anxiety and psychosis". The report continues that of the number of patients who mentioned cannabis use to their GP, 48% had a psychological problem, including 19% with depression, 9% with psychosis and 6% had anxiety. However, it was also noted that few cannabis users actually tell their doctors that they use it, which could potentially bias the results of the study. Much of the evidence for a short-lived cannabis psychosis is largely based on case reports where heavy cannabis use has preceded the onset of a psychotic episode, which then remits on abstinence. Depictions of a toxic or acute cannabis psychosis have been reported in a number of countries such as New Zealand, South Africa, Sweden and the UK.

Psychosis

A large, unselected population-based study, published in British Journal of Psychiatry (2008), examined cannabis use and prodromal symptoms of psychosis at age 15–16 years and concluded that cannabis use was associated with prodromal

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...

symptoms of psychosis

Psychosis

Psychosis means abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality"...

in adolescence.

The direction of causation was more directly examined in a study by Dr. Mikkel Arendt of Aarhus University in Risskov, Denmark, and colleagues, which found that individuals treated for psychotic episodes following cannabis use had the same likelihood of having a mother, sister or other "first-degree" relative with schizophrenia as did the individuals who had actually been treated for schizophrenia themselves. This suggests that the psychosis blamed on cannabis use is in fact the result of a genetic predisposition towards schizophrenia. "These people would have developed schizophrenia whether or not they used cannabis"

In a recent study at the Institute of Psychiatry at King's College London, scientists have confirmed a link between potent cannabis use ("skunk" cannabis, which accounts for 80 per cent of street seizures of the drug in the UK) and transient psychotic symptoms in healthy people. After testing 22 healthy males in their late 20s by injecting them with THC, with a control dummy injection administered to a percentage of the sample group, a link was found between the chemical and psychosis, "in which hallucinations leave sufferers unable to know what is real and what is imagined". Dr Paul Morrison, who led the team, concluded, "these findings confirm that THC can induce a transient acute psychological reaction in psychiatrically well individuals". In addition, it was found that the extent of the psychotic reaction was not related to "the degree of anxiety or cognitive impairment" in the sample group. Further research is needed into the chemical makeup of skunk cannabis as it is believed stronger strains have virtually no traces of CBD (cannabidiol), which appears to counteract the damaging effects of THC. However, there is likely to be wide variation in the THC and CBD levels (and ratios) since numerous (perhaps even hundreds) of different strains of cannabis have been marketed by dealers as "skunk", some of which are descended from the original 1980s Amsterdam variety.

The largest longitudinal study examining the link between cannabis and psychosis was undertaken by Andreasson and colleagues and followed 45,570 male Swedish Army

Swedish Army

The Swedish Army is one of the oldest standing armies in the world and a branch of the Swedish Armed Forces; it is in charge of land operations. General Sverker Göranson is the Supreme Commander-in-Chief of the Army.- Organization :...

conscripts for 15 years. After controlling for other factors such as parental mental illness or a pre-existing psychotic illnes at conscription, the study found that the odds of developing schizophrenia later in life were "1.5 times higher for those who had used cannabis 1-10 times and 2.3 times more likely for those who had used cannabis 10 times or more". Further to criticism that the study did not control for the use of other potentially psychotogenic substances such as amphetamine

Amphetamine

Amphetamine or amfetamine is a psychostimulant drug of the phenethylamine class which produces increased wakefulness and focus in association with decreased fatigue and appetite.Brand names of medications that contain, or metabolize into, amphetamine include Adderall, Dexedrine, Dextrostat,...

s, a follow-up study re-analysed the data and ruled out this argument, finding that cannabis use remained predictive of schizophrenia in a dose-dependent manner even after accounting for other substance use and pre-morbid social integration.

A 2005 meta analysis of available data which evaluated several hypotheses regarding the correlation of cannabis and psychosis found that there is no support for the hypothesis that cannabis can cause cases of psychosis which would not have occurred otherwise, however further study is needed to explore the correlation between cannabis and other types of psychosis patients. Studies have shown that a risk does exist in some individuals with a predisposition to mental illness to develop symptoms of psychosis

Psychosis

Psychosis means abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality"...

. The risk was found to be directly related to high dosage and frequency of use, early age of introduction to the drug, and was especially pronounced for those with a predisposition for mental illness. These results have been questioned as being biased by failing to account for medicinal versus recreational usage — critics contend it could be a causal relationship, or it could be that people who are susceptible to mental problems tend to smoke cannabis, or it could be connected to the criminalization of cannabis. Another important question is whether the observed symptoms of mental illness are actually connected to development of a permanent mental disorder; cannabis may trigger latent conditions, or be part of a complex coordination of causes of mental illness, referred to in psychology

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...

as the 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....

. People with developed psychological disorders are known to self-medicate their symptoms with cannabis as well, although one study has claimed that those with a predisposition for psychosis did not show a statistically significant increase in likelihood of cannabis use four years later.

Correlation versus causation

Some studies conclude that there is a correlation of cannabis use and some symptoms of psychosis, but do not necessarily support the notion that cannabis use is a sufficient or necessary cause for psychosis. It might be a component cause, part of a complex constellation of factors leading to psychosis, or it might be a correlation without forward causality at all.

For example, a review of the evidence by Louise Arsenault, et al., in 2004 reports that on an individual level, cannabis use confers an overall twofold increase in the relative risk of later schizophrenia, assuming a causal relationship. This same research also states that "There is little dispute that cannabis intoxication can lead to acute transient psychotic episodes in some individuals". The study synthesizes the results of several studies into a statistical model. The study does not correct for the use of other illicit drugs, and relies on self-reporting of cannabis dosage. The study also does not determine if the cannabis use preceded or followed the mental health problem.

Similarly, the landmark study, in 1987, of 50,000 Swedish Army conscripts, mentioned earlier, found that those who admitted at age 18 to having taken cannabis on more than 50 occasions, were six times more likely to develop schizophrenia in the following 15 years. In fact, psychosis cases were restricted to patients requiring a hospital admission. These findings have not been replicated in another population based sample. As the study did not control for symptoms preexisting onset of cannabis use, the use of other illicit drugs, the study does not resolve the correlation versus causality question but has fueled a major debate within the scientific community. This study also used self reporting for cannabis dosage.

A 2005 study found that "the onset of schizotypal symptoms generally precedes the onset of cannabis use. The findings do not support a causal link between cannabis use and schizotypal traits". A 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:...

is a personality disorder

Personality disorder

Personality disorders, formerly referred to as character disorders, are a class of personality types and behaviors. Personality disorders are noted on Axis II of the Diagnostic and Statistical Manual of Mental Disorders or DSM-IV-TR of the American Psychiatric Association.Personality disorders are...

different from schizophrenia, though there is some evidence that the former may predispose to the latter. A 2007 British study concluded, "We found few appreciable differences in symptomatology between schizophrenic patients who were or were not cannabis users. There were no differences in the proportion of people with a positive family history of schizophrenia between cannabis users and non-users. This argues against a distinct schizophrenia-like psychosis caused by cannabis."

Research based on the Dunedin Multidisciplinary Health and Development Study

Dunedin Multidisciplinary Health and Development Study

The Dunedin Multidisciplinary Health and Development Study is a long-running cohort study of 1037 people born over the course of a year in Dunedin, New Zealand....

has found that those who begin regular use of cannabis in early adolescence (from age 15, median

Median

In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...

25 days per year by age 18) and also fit a certain genetic

Genetics

Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

profile (specifically, the Val/Val variant of the COMT gene) are five times more likely to develop psychotic illnesses than individuals with differing genotypes, or those who do not use cannabis. The study was noted for having controlled for preexisting symptoms, but is open to the criticism that it cannot control for late adolescent onset of psychotic illness. Also, the study was on a cohort population

Cohort study

A cohort study or panel study is a form of longitudinal study used in medicine, social science, actuarial science, and ecology. It is an analysis of risk factors and follows a group of people who do not have the disease, and uses correlations to determine the absolute risk of subject contraction...

, so there is no way to correlate a change in the rate of adolescent use with a change in the rate of incidence of schizophrenia in the study population. These points undermine its value in resolving the correlation versus causality question.

A study that inversely correlated cerebrospinal anandamide

Anandamide

(an endogenous cannabinoid) levels with severity of schizophrenia (i.e., that anandamide was released in order to suppress psychosis) suggests that cannabis use may be an effect of schizophrenia or its predisposition, as opposed to a cause.

Cannabis use does not appear to be causally related to the incidence

Incidence (epidemiology)

Incidence is a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate with a denominator.Incidence proportion is the...

of schizophrenia, but its use is highly likely to precipitate psychotic disorders in persons who are vulnerable to developing psychosis; and cannabis use is also likely to worsen the course of the disorder among those who have already developed it.

Mood disorders

Less attention has been given to the association between cannabis use and depression, though it is possible this is because cannabis users who suffer from depression are less likely to access treatment than those suffering from psychosis. Chen and colleagues (2002) re-analyzed the US National Comorbidity Survey (NCS) to examine the relationship between cannabis use and a major depressive episode and discovered that some degree of cannabis dependence was associated with a 3.4 time greater risk of major depression. Similarly, data retrieved from the US Longitudinal Alcohol Epidemiologic Survey showed that cannabis dependency within the past year was associated with a 6.4 fold chance of also receiving a diagnosis for major depression in that time. The issue of suicide and cannabis use is considered by Borges, Walters, and Kessler who examined whether cannabis use heightens the risk of suicide or attempted suicide. Cross-sectional data from the US National Comorbidity Survey indicated that cannabis-dependent individuals were 2.4 times more likely to report a suicide attempt than non-cannabis-dependent individuals, after controlling for socio-demographic factors, psychiatric disorders and other drug use. Beautrais et al. (1999) examined 302 hospitalized cases of suicide attempts and found that 16% screened positive for cannabis abuse or dependence, compared with 2% of a random community sample. After controlling for depression and social disadvantage the study found this translated to a twofold suicide attempt risk for those who had a cannabis use disorder.

A 2005 literature review of the use of cannabis in mental health patients found that the drug can have very different effects on different patients. Although "no controlled trials of THC have been done in bipolar disorder", there is anecdotal evidence that "for some people marijuana is beneficial" as a treatment for bipolar disorder. The reviewers suggested that randomized studies and standardized administration techniques would be required to create conclusive evidence.

A USC study of 4,400 Internet users found that "adults apparently do not increase their risk for depression by using marijuana", and in fact show fewer self-reported symptoms of depression.

Cannabidiol in the treatment of schizophrenia

A recent study has shown that cannabidiol

Cannabidiol

Cannabidiol is a cannabinoid found in Cannabis. It is a major constituent of the plant, representing up to 40% in its extracts.It has displayed sedative effects in animal tests...

(a major constituent of cannabis) may be as effective as atypical antipsychotics in treating schizophrenia. Further research has verified these results. Leweke et al., (2009) performed a double blind, 4 week, explorative study controlled clinical trial, to compare the effects of purified cannabidiol and the atypical antipsychotic amisulpride

Amisulpride

Amisulpride , is an atypical antipsychotic used to treat psychosis in schizophrenia and episodes of mania in bipolar disorder. In small doses it is also used to treat depression. It was introduced by Sanofi-Aventis in the 1990s.-Pharmacology:Amisulpride functions primarily as a D2 and D3 receptor...

on improving the symptoms of schizophrenia in 42 patients with acute paranoid schizophrenia. 'Both treatments were associated with a significant decrease of psychotic symptoms after 2 and 4 weeks as assessed by BPRS and PANSS. However, there was no statistical difference between both treatment groups. In contrast, cannabidiol induced significantly less side effects (EPS, increase in prolactin, weight gain) when compared to amisulpride'. The authors conclude cannabidiol revealed substantial antipsychotic properties in acute paranoid schizophrenia (Leweke et al., 2009). This led the authors to suggest the endocannabinoid system

Endocannabinoid system

The endocannabinoid system refers to a group of neuromodulatory lipids and their receptors that are involved in a variety of physiological processes including appetite, pain-sensation, mood, and memory; it mediates the psychoactive effects of cannabis and, broadly speaking, includes:* The...

plays an adaptive role in the development of paranoid schizophrenia and that this research provides evidence that this mechanism may be a valuable target for 'antipsychotic treatment strategies' .

A 2008 study published in the British Journal of Psychiatry showed significant differences in Oxford-Liverpool Inventory of Feelings and Experiences scores between three groups: The first consisted of non-cannabis users, the second of users who tested positive for Δ9-THC

THC

THC commonly refers to tetrahydrocannabinol, the main active chemical compound in Cannabis.THC may also refer to:* Tan Holdings Corporation...

only, and the third consisted of users who tested positive for both Δ9-THC and CBD. The Δ9-THC only subset scored significantly higher for unusual experiences, while users of both Δ9-THC and CBD had much lower introvertive 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....

scores .

Respiratory problems

Although cannabis smoke is not nearly as harmful as tobacco

Tobacco

Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...

smoke, smoking is the most harmful method of cannabis consumption, as the inhalation of smoke from organic materials

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

can cause various health problems (e.g., coughing and sputum

Sputum

Sputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....

). By comparison, studies on the vaporization of cannabis found that subjects were "only 40% as likely to report respiratory symptoms as users who do not vaporize, even when age, sex, cigarette use, and amount of cannabis consumed are controlled." Another study found vaporizers to be "a safe and effective cannabinoid delivery system."

The term cannabis-associated respiratory disease

Cannabis-associated respiratory disease

Cannabis-associated respiratory disease can refer to neoplastic processes or to structural damage to the lung.It is often compared to the damage done by tobacco, but it is the subject of much less study...

can refer to neoplastic (tumor-forming) processes or structural damage in the lung.

However, recent studies have shown that there are no links between the regular smoking of marijuana and cancer.

Smoking cessation

Cannabis is the most widely used illicit drug in the Western world. There is plenty of documented evidence to suggest a need for users to find ways to assist them to stop using cannabis and the demand for treatment for cannabis dependency is increasing internationally. There are a number of ways to quit cannabis and increasing evidence-based treatments for cannabis users wishing to change the patterns of their use. This article deals with the different interventions to assist in the cessation of cannabis use.

Behavioral effects

Government studies often point to statistical data accumulated by methods like the National Household Survey on Drug Abuse (NHSDA), the Monitoring the Future

Monitoring the Future

The Monitoring the Future study, also known as the National High School Senior Survey, is a long-term epidemiological study that surveys trends in legal and illicit drug use among American adolescents and adults as well as personal levels of perceived risk and disapproval for each drug...

study (MTF), and the Arrestee Drug Abuse Monitoring

Arrestee Drug Abuse Monitoring

Arrestee Drug Abuse Monitoring, or ADAM, was a survey conducted by the U.S. Department of Justice to gauge the prevalence of alcohol and illegal drug use among prior arrestees...

(ADAM) program, which claim lower school averages and higher dropout

Dropping out

Dropping out means leaving a group for either practical reasons, necessities or disillusionment with the system from which the individual in question leaves....

rates among users than non-users. However, the major contributor to a lack of credibility in these studies, is that in many cases, like with NHSDA and MTF, these surveys are usually self-administered and may be anonymous. The likeliness of over- or under-representing data definitely undermines the effectiveness of these instruments. The ADAM study is conducted anonymously, but only seeks information from a sample of people who have been arrested for drug-related offenses. Socially deviant behavior may be found more frequently in individuals of the criminal justice system compared to those in the general population, including non-users. In response, independent studies of college students have shown that there was no difference in grade point average, and achievement, between marijuana users and non-users, but the users had a little more difficulty deciding on career goals, and a smaller number were seeking advanced professional degrees. Laboratory studies of the relationship between motivation and marijuana outside of the classroom, where volunteers worked on operant tasks for a wage representing a working world model, also fail to distinguish a noticeable difference between users and non-users.

A longitudinal study

Longitudinal study

A longitudinal study is a correlational research study that involves repeated observations of the same variables over long periods of time — often many decades. It is a type of observational study. Longitudinal studies are often used in psychology to study developmental trends across the...

of the long-term effects of cannabis usage from ages 14 to 21 on life outcomes up to age 25 in a Christchurch

Christchurch

Christchurch is the largest city in the South Island of New Zealand, and the country's second-largest urban area after Auckland. It lies one third of the way down the South Island's east coast, just north of Banks Peninsula which itself, since 2006, lies within the formal limits of...

, New Zealand birth cohort

Cohort (statistics)

In statistics and demography, a cohort is a group of subjects who have shared a particular time together during a particular time span . Cohorts may be tracked over extended periods in a cohort study. The cohort can be modified by censoring, i.e...

concluded, "The results of the present study suggest that increasing cannabis use in late adolescence and early adulthood is associated with a range of adverse outcomes in later life. High levels of cannabis use are related to poorer educational outcomes, lower income, greater welfare dependence and unemployment and lower relationship and life satisfaction. The findings add to a growing body of knowledge regarding the adverse consequences of heavy cannabis use."

Gateway drug hypothesis

The gateway drug

Gateway drug

The gateway drug theory is the hypothesis that the use of less deleterious drugs may lead to a future risk of using more dangerous hard drugs and/or crime...

hypothesis asserts that the use of cannabis may ultimately lead to the use of harder drugs

Hard and soft drugs

Hard and Soft drugs are terms to distinguish between psychoactive drugs that are addictive and perceived as especially damaging and drugs that are believed to be non-addictive and with fewer dangers associated with their use...

. For the most part, it was commonly thought that cannabis gateways to other drugs because of social

Sociology

Sociology is the study of society. It is a social science—a term with which it is sometimes synonymous—which uses various methods of empirical investigation and critical analysis to develop a body of knowledge about human social activity...

factors. For example, the criminalization

Criminalization

Criminalization or criminalisation, in criminology, is "the process by which behaviors and individuals are transformed into crime and criminals". Previously legal acts may be transformed into crimes by legislation or judicial decision...

of cannabis in many countries associates its users with organized crime

Organized crime

Organized crime or criminal organizations are transnational, national, or local groupings of highly centralized enterprises run by criminals for the purpose of engaging in illegal activity, most commonly for monetary profit. Some criminal organizations, such as terrorist organizations, are...

promoting the illegal drug trade

Illegal drug trade

The illegal drug trade is a global black market, dedicated to cultivation, manufacture, distribution and sale of those substances which are subject to drug prohibition laws. Most jurisdictions prohibit trade, except under license, of many types of drugs by drug prohibition laws.A UN report said the...

.

A study of twins by researchers at Virginia Commonwealth University

Virginia Commonwealth University

Virginia Commonwealth University is a public university located in Richmond, Virginia. It comprises two campuses in the Downtown Richmond area, the product of a merger between the Richmond Professional Institute and the Medical College of Virginia in 1968...

showed that cannabis use in adolescence strongly predicted later use of multiple drugs. The main causation was tied to shared environmental and genetic vulnerability, but there was some evidence for a causal role of cannabis.
A July 2006 study by Ellgren et al. strictly tested lab rats for the biological mechanism of the gateway drug effect. The study administered 6 "teenage

Adolescence

Adolescence is a transitional stage of physical and mental human development generally occurring between puberty and legal adulthood , but largely characterized as beginning and ending with the teenage stage...

" (28 and 49 days old) rats delta-9-tetrahydrocannabinol, and 6 were the control

Scientific control

Scientific control allows for comparisons of concepts. It is a part of the scientific method. Scientific control is often used in discussion of natural experiments. For instance, during drug testing, scientists will try to control two groups to keep them as identical and normal as possible, then...

. One week after the first part was completed, catheters were inserted in the jugular vein

Jugular vein

The jugular veins are veins that bring deoxygenated blood from the head back to the heart via the superior vena cava.-Internal and external:There are two sets of jugular veins: external and internal....

of all of the adult rats and they were able to self-administer themselves heroin by pushing a lever. The study found that initially both groups behaved the same and began to self-administer heroin frequently, but then stabilized at different levels. The rats that had previously been administered THC consumed about 1.5 times more heroin than those that had not. Because many THC receptors interact with the opioid system, the study surmised that adolescent cannabis use overstimulates and alters the pleasure and reward structures of the brain, thus increasing the already high risk of addiction for people who start to use heroin. However, the rats took up self-administration at the same rate regardless of adolescent THC exposure, and observed levels of "drug-seeking behavior" were also the same. Psychopharmacologist

Psychopharmacology

Psychopharmacology is the scientific study of the actions of drugs and their effects on mood, sensation, thinking, and behavior...

Ian Stolerman, from King's College London

King's College London

King's College London is a public research university located in London, United Kingdom and a constituent college of the federal University of London. King's has a claim to being the third oldest university in England, having been founded by King George IV and the Duke of Wellington in 1829, and...

, finds the biological cannabis gateway drug effect "somewhat preliminary", and states "it's too early to say there's a consensus, but a small number of studies like this suggest that there is a physiological basis for this effect." Other drugs, he notes, such as cocaine and amphetamines are involved in another brain pathway called the dopaminergic system. Cells in that system also interact with THC receptors and could be modified by cannabis exposure. Cannabinoid receptors are 10 times more prevalent in the brain than opioid receptors. According to Dr. Hurd, one of the study leaders, two other drugs that also stimulate opioid cells, and could therefore also feasibly cause a gateway effect, are 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...

and 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....

.

However, a December 2006 study by 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...

challenges these findings. A 12 year study on 214 boys from ages 10–12 showed that adolescents who used marijuana prior to using other drugs, including alcohol and tobacco, were no more likely to develop a substance abuse disorder than other subjects in the study. "This evidence supports what's known as the common liability model… states the likelihood that someone will transition to the use of illegal drugs is determined not by the preceding use of a particular drug, but instead by the user's individual tendencies and environmental circumstances", investigators stated in a press release. They added, "The emphasis on the drugs themselves, rather than other, more important factors that shape a person's behavior, has been detrimental to drug policy and prevention programs."

Models used in a 2002 study by RAND

RAND

RAND Corporation is a nonprofit global policy think tank first formed to offer research and analysis to the United States armed forces by Douglas Aircraft Company. It is currently financed by the U.S. government and private endowment, corporations including the healthcare industry, universities...

cast doubt on the gateway effect and show "that the marijuana gateway effect is not the best explanation for the link between marijuana use and the use of harder drugs", as noted by Andrew Morral, associate director of RAND's Public Safety and Justice unit and lead author of the study.

Memory and intelligence

A 2002 longitudinal study

Longitudinal study

published in the Canadian Medical Association Journal
Canadian Medical Association Journal
The Canadian Medical Association Journal is a general medical journal that is published biweekly by the Canadian Medical Association . It covers research and ideas aimed at improving health for people in Canada and globally. CMAJ publishes original clinical research, analyses and reviews, news,...

concluded that "marijuana does not have a long-term negative impact on global intelligence", and that "current marijuana use had a negative effect on global IQ score only in subjects who smoked 5 or more joints per week." The study, which monitored subjects since birth, examined IQ scores before, during and after cessation of regular marijuana use. It found current light users and former users showed average IQ gains of 5.8 and 3.5 respectively, compared to an IQ gain of 2.6 for those who had never used cannabis. The study did however show an average IQ decrease of 4.1 for heavy users.

A 2008 study suggested that long-term, heavy cannabis use (over five joints daily for more than ten years) are associated with structural abnormalities in the 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 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.-...

areas of the brain.
The hippocampus, thought to regulate emotion and memory, and the amygdala, involved with fear and aggression, tended to be smaller in heavy and long-term cannabis users than in controls. For heavy users participating in the study, volume was an average of 12 percent lower in the hippocampus and 7.1 percent lower in the amygdala. However, the sample size of the study was small, with only 31 participants total (15 heavy users and 16 non-users). The study concluded that "heavy daily cannabis use across protracted periods exerts harmful effects on brain tissue and mental health", however there was a lack of prior brain testing. According to commentary provided by the National Cannabis Prevention and Information Centre

National Cannabis Prevention and Information Centre

The National Cannabis Prevention and Information Centre or NCPIC, is an Australian centre funded by the Commonwealth Department of Health and Ageing....

(NCPIC), these brain regions are intricately involved in learning and memory processes and are considered core components of the emotional brain and the research found that in addition left hippocampal and amygdala volume was inversely associated with cumulative doses of cannabis over the previous 10 years, as well as subthreshold positive psychotic symptoms. In their commentary, NCPIC state: "While modest use may not lead to significant neurotoxicity, these results corroborate similar findings within the animal literature and indicate that heavy daily cannabis use over protracted periods exerts harmful effects on brain tissue and mental health". An earlier 1998 report by INSERM and CNRS, which was directed by Dr. Pierre-Bernard Roques, determined that, "former results suggesting anatomic changes in the brain of chronic cannabis users, measured by tomography, were not confirmed by the accurate modern neuro-imaging techniques

Neuroimaging

Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function/pharmacology of the brain...

(such as MRI) ... Moreover, morphological impairment of the hippocampus [which plays a part in memory and navigation] of rat after administration of very high doses of THC was not shown."

A 2002 study published in Neurology concluded that "very heavy use of marijuana is associated with persistent decrements in neurocognitive performance even after 28 days of abstinence."

The strongest evidence regarding cannabis and memory focuses on its non-acute negative effects on short-term and working memory. Evidence also suggests that long-term effects exist, but these appear to be reversible except possibly in very heavy users.

A 1998 Journal of Neuroscience in vitro

In vitro

In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...

research, which was carried out on hippocampal cells excised from decapitated rats, using THC carried in ethyl alcohol to saturate the neurons, suggests that THC is toxic for cultured hippocampal neurons.

External links

Cannabis Use and Psychosis from National Drug and Alcohol Research Centre, Australia
The key research on cannabis use and mental illness at BBC News
Provision of Marijuana and Other Compounds For Scientific Research recommendations of The National Institute on Drug Abuse National Advisory Council
The Brain's Own Marijuana Scientific American (December 2004)
Ramström, J. (2003), Adverse Health Consequences of Cannabis Use, A Survey of Scientific Studies Published up to and including the Autumn of 2003, National institute of public health, Sweden, Stockholm.
Hall, W., Solowij, N., Lemon, J., The Health and Psychological Consequences of Cannabis Use. Canberra: Australian Government Publishing Service; 1994.
World Health Organisation, PROGRAMME ON SUBSTANCE ABUSE, Cannabis: a health perspective and research agenda;1997.
Cannabis and mental health factsheet
Bibliography of scholarly histories on cannabis and hashish. (Updated to include article abstracts.)
Marijuana and Immunity
The National Cannabis Prevention and Information Centre (Australia)
EU Research paper on the potency of Cannabis (2004)(.pdf)
Driving under the influence of cannabis: a brief review of the literature
Cannabis Contamination Research Brief
Cannabinoids and appetite
NCPIC e-zine December 2007/ January 2008 Commentary on cannabis toxicity research and Moir report
Cannabis use and reproduction
Evidence-based answers to cannabis questions
NCPIC Cannabis and alcohol factsheet
Fast Facts on Mental Health + Cannabis National Cannabis Prevention and Information Centre (Australia)

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Reproductive and endocrine effects

Pregnancy

Cannabis dependency

Withdrawal

Mental health

Psychosis

Correlation versus causation

Mood disorders

Cannabidiol in the treatment of schizophrenia

Respiratory problems

Smoking cessation

Behavioral effects

Gateway drug hypothesis

Memory and intelligence

See also

External links