Oakley Ray, PhD, Emeritus Professor of Psychology and Pharmacology at Vanderbilt University, and Charles Ksir, PhD, Professor Emeritus of Psychopharmacology and Drug Policy at the University of Wyoming, wrote in their 2004 textbook Drugs, Society and Human Behavior:

“There have been reports of psychotic ‘breakdowns’ occurring with rare frequency after marijuana has been smoked, but the causal relationship is in question.

The psychotic episodes are generally self-limiting and seem to occur in individuals with a history of psychiatric problems.”