Understanding the Relationship Between Amphetamines and Psychosis | SpringerLinkMost people with psychosis, who use stimulants, also use cannabis, and cannabis is the most commonly used illicit drug among first-episode schizophrenia cases [40, 44, 45, 46, 48, 49, 50]. A recent review of stimulant-use disorders in people with psychosis found that cannabis use was the variable that most strongly correlated with stimulant use [51•]. Cannabis and methamphetamine have been suggested as the two most important drugs involved in the pathogenesis of psychosis and schizophrenia . As the effect of cannabis, to a certain extent, counters that of amphetamines, users often take it to end amphetamine binges. Studies on psychosis in users of amphetamines seldom report on concurrent cannabis use. Given that cannabis often accompanies the use of amphetamines, it is uncertain to what extent the effect of cannabis might have influenced the evidence on the association between amphetamines and psychosis.