There is a link between psychosis and the use of illegal substances such as cannabis - people with psychosis are much more likely to use illegal substances, and also to suffer poorer outcomes because of this.14
Some people turn to illegal substances as a means of coping with symptoms.14 Up to a quarter of people with schizophrenia have a cannabis problem.23
However, the question of whether the use of cannabis directly causes psychosis is a controversial one. The evidence is conflicting, and where research does suggest a link to psychosis, it has not been able to give conclusive scientific proof of a causal relationship with cannabis.24,25
There is consensus, though, that cannabis and other substance misuse worsens the health of people with psychosis, and guidelines in the UK, for example, recommend that healthcare professionals offer help with both the psychosis and any substance use.14
Written by Markus MacGill