Researchers at the University of Montreal in Canada conducted a meta-analysis of current research to test the schiophrenia self-medication hypothesis – the idea that there are high rates substance abuse among those with schizophrenia because drugs such as marijuana, nicotine, etc. are a way to relieve symptoms of the disorder. Their findings are published in April’s Psychological Medecine.

They used search engines to mathematically analyze data from 11 studies that assessed negative symptoms in patients with schizophrenia and substance abuse disorders, using the Scale for the Assessment of Negative Symptoms (SANS), and found a moderate effect. Those with substance abuse disoders had fewer negative symptoms compared to those who were abstinent. These results suggest that either substance abuse relieves the negative symptoms of schizophrenia or that the patients with fewer negative symptoms would be more prone to substance use disorders.