Previous studies have found that cannabis users were more likely to develop psychotic disorders than non-cannabis users, but were unable to determine a causal relationship between use of the drug and psychosis. A new study suggests that there is no causal link.
In the new study, by comparing families with and without a history of marijuana use, the Harvard researchers were able to address this question.
They recruited four groups:
-87 non-psychotic people who had used no drugs.
-84 non-psychotic people who had used marijuana.
-32 patients who had schizophrenia but hadn’t used drugs.
-76 patients with schizophrenia who had used marijuana.
They then looked at the relatives of those with schizophrenia in comparison to the relatives of those in the control groups.
The results showed an increased risk of developing schizophrenia in the relatives of patients who already had schizophrenia, whether or not those patients used marijuana.
This study, then, finds no evidence that marijuana is associated with developing schizophrenia.
Full Story: PsyBlog: Marijuana Does Not Cause Schizophrenia