Cannabis Linked to Psychotic Disorders

Numerous earlier studies have found that people who use cannabis (marijuana) and other illicit drugs frequently suffer from some form of an early onset psychotic disorder. In the present study, the researchers intended to analyze all these studies in detail and to establish the relationship between the use of cannabis, alcohol and other psychoactive substances with the early onset of psychosis. Various published studies reporting age at onset of psychotic illness in substance-using and non-substance-using groups were located using searches of a number of medical journal databases. Statistical analysis was done on the data obtained from 83 such studies. It was found that the use of cannabis and other illicit substances was associated with an earlier age of onset of psychotic disorders, particularly schizophrenia.

The National Survey on Drug Use and Health, conducted in 2009, has reported that more than 16 million Americans are addicted to cannabis. In fact, it is the most commonly used addictive substance after alcohol and tobacco. It was found that many people who use cannabis started using the drug in their teen age years. Various prior surveys have consistently found that use of these drugs is associated with early onset of psychotic disorders, such as schizophrenia. In the present study, the researchers analyzed various published reports and tried to determine the age of onset of psychotic disorders in substance users and non-substance users. They also wanted to know whether there are any other contributory factors for the development of psychotic problems in substance abusers.

* Five journal databases (CINAHL, EMBASE, MEDLINE, PsycINFO, and ISI Web of Science) were searched to get various published studies that were conducted to find out the age of onset of psychosis in users of various illicit drugs. Eighty three studies were finally selected to be included in this analysis.
* The number of users and non-users included in the published reports, the proportion of people who used cannabis, and the number of people who had some form of psychotic disorder was recorded.
* Extensive statistical analysis was done to find out the age of onset of psychotic illnesses in people with a history of substance abuse, using psychoactive substances, and others with no such history.

* In the 83 papers that were studied, a total of 131 samples of the mean age at onset of psychosis in substance-using and non-substance-using individuals was collected, which included 8,167 substance users and 14,352 non-substance users.
* Meta-analysis of age at onset of psychosis revealed that the age of onset was 2.70 years earlier among samples of cannabis users and was two years earlier in samples with unspecified substance use compared with non–substance-using controls.
* Women who used cannabis developed psychosis much earlier (3.40 years) compared to male users (1.87 years)
* Use of alcohol alone was not associated with younger age of onset of psychosis.

Shortcomings/Next steps
Sufficient data regarding the use of tobacco was not available for statistical analysis. Tobacco is also known to damage the brain, which may add to the early onset of psychosis in tobacco users. In addition, researchers could not ascertain the causal role of cannabis in producing psychosis. They could only find the association between the two. Further studies are necessary to identify the molecular mechanisms involved in the early onset of psychosis in relation to drug use.

This study supports the concept that the use of cannabis is associated with early onset of psychotic disorders. It is evident that by decreasing or abstaining from the use of cannabis, one can delay or prevent the occurrence of psychotic disorders. In some adolescents in whom the development of psychosis is inevitable due to family history or genetic causes, avoiding drugs like marijuana may put off possible brain damage by two to three years. This helps in decreasing the long term disabilities arising because of psychotic disorders. “The results suggest the need for renewed warnings about the potentially harmful effects of cannabis.”

For More Information:
Cannabis Use and Earlier Onset of Psychotic Disorders
Publication Journal: Archives of General Psychiatry, February 2011
By Matthew Large; Swapnil Sharma; Mental Health Service, Prince of Wales Hospital and the School of Psychiatry, University of New South Wales, Sydney, Australia

*FYI Living Lab Reports Are Summaries of the Original Research.


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