Forty-Six Cases of Psychosis in Cannabis Abusers Gunila Bernhardson

Forty-six habitual users of cannabis, who had been treated for psychosis during the years 1966-1970, were reported following an inquiry sent to Swedish psychiatric clinics and mental hospitals. Twenty-four of these cases had had psychotic episodes generally lasting 1-5 weeks, whereas 22 cases were running a chronic course. In 14 chronic cases an endogenous psychosis seemed to have been present before the drug debut. Seven of these showed a marked aggravation of the psychotic symptoms during periods of cannabis abuse. Eight cases of chronic psychosis occurred in earlier nonpsychotic subjects.Thirty cases occurred in formerly nonpsychotic individuals, though 23 of them had shown psychoneurotic traits. In seven of these, relapse into a second psychotic episode occurred following renewed cannabis abuse. The symptomatology reminded one of schizophrenic or manic-depressive endogenous psychoses in most instances, but confusional states were also seen. Evidence supporting the existence of a cannabis-induced psychosis has been discussed.