Cannabis Psychosis

Summary There is clear evidence from countries where heavy use of cannabis is common, that it can cause a short‐lived, toxic psychosis characterized by confusion, delusions, hallucinations and emotional lability. This clinical experience is supported by laboratory experiments showing that, A‐P tetrahydrocannabinol (THC), the most active constituent of cannabis, has dose‐related psychotomimetic effects. Evidence that cannabis causes a functional, paranoid psychosis or a chronic psychosis that persists after drug use ceases, is much less convincing although regular, heavy users may suffer repeated short episodes of psychosis and effectively maintain themselves in a chronic psychotic condition. Prolonged effects such as flashbacks and depersonalization may occur because cannabis and its metabolites are eliminated only very slowly from the body. Reports of such consequences, at present often dismissed as anecdotal, therefore, warrant careful attention and analysis.