Epidemiological studies have suggested that use of cannabis may increase the risk of developing schizophrenia
(1). However, an earlier literature, still controversial,suggests that abuse of methamphetamine could also trigger the development of persistent psychotic syndromes
(2). Clinical investigations in Japan describing persistent psychosis in some methamphetamine users long after drug withdrawal support this possibility
(3). In Western psychiatry, however, a prolonged psychosis in the drug-free state is not generally viewed as a feature of chronic methamphetamine exposure, and when such a psychosis is observed, it is thought to be explainable in toto by a preexisting (undiagnosed) psychotic disorder
(4). Nevertheless, two Clinical Case Conference articles in this journal, spanning a 14-year period, have focused specifically on the still unresolved possibility that methamphetamine exposure may induce a persistent psychotic state (5, 6).