A study just published in the Archives of General Psychiatry sheds some light on a relationship between cannabis and schizophrenia. The research compared data from 83 studies of the onset of mental disorders, comprised of 8200 patients who were using alcohol and illegal drugs and 14,450 patients who were not. Most of the participants in the study had been diagnosed with schizophrenia.
The study found that the patients who had used marijuana showed symptoms 2.7 years earlier, on average, when compared with those who did not use illegal drugs. Since the onset of schizophrenia is usually in the late teens or early 20’s, the loss of an average 2.7 years* could have a major effect on the individual’s life, in terms of failure to finish school, training for employment and so forth, prior to the onset of psychosis.
Schizophrenia is known to be genetic in over 80% of cases, and the researchers do not suggest that the cannabis causes the disorder (although other researchers have suspected a connection in heavy cannabis users). It seems, however, that it can trigger early onset in those who already have a predisposition.
*An average loss of 1.9 years for men, and 3.4 for women.