Is there really a link between marijuana and schizophrenia? Research is mixed - but a link exists between marijuana use in some people and schizophrenic-like symptoms.
One 2005 study, for example, found similarities between the brains of adolescents who smoked marijuana regularly and adolescents with schizophrenia. Researchers at North Shore University Hospital-Long Island Jewish Healthcare System found that found that a brain region that connects the front of the brain to deeper regions (the arcuate nucleus) is underdeveloped in both schizophrenia patients and regular marijuana users.The under-development was only on the left side in these teenagers, while schizophrenia patients who also abuse marijuana showed under-development on both sides of the brain.
Other studies have found that THC can cause schizophrenia-like symptoms in some. Most experts do not believe this. It is more likely that marijuana can trigger the emergence of schizophrenia in persons who are already predisposed to developing schizophrenia. This probably includes anyone with a strong family history of schizophrenia. An April 2006 review of the research concluded that:
There is evidence for an association between cannabis and psychosis. It is clear that cannabinoids can cause acute transient psychotic symptoms or an acute psychosis. Also it is clear that cannabis can exacerbate psychosis in individuals with an established psychotic disorder. However, whether cannabis causes a persistent de novo psychosis independent of any other risk factors is not supported by the existing literature. More likely, cannabis is a component cause that interacts with other factors (e.g., genetic risk) to induce psychosis. (Malik & D'Souza, 2006)
What should you do based on this research? If schizophrenia runs in your family, then you should avoid marijuana. If you react to marijuana with extreme paranoia or any schizophrenic-like symptoms you should also consider avoiding this drug.
Source: Research summary of Ashtari and Kumra, paper presented at the Radiological Society of North America's annual meeting in Chicago, November, 2005; Asif R. Malik, MD, and Deepak Cyril D'Souza, MD - Gone to Pot: The Association Between Cannabis and Psychosis. Psychiatric Times April 2006, Vol. XXIII, No. 4.