Marijuana use in schizophrenia: a clear hazard

The use of marijuana as the independent variable produced a serious exacerbation of a psychotic process in four schizophrenic patients whose illness was otherwise well controlled with antipsychotic medication. Each patient served as his own control--the sole substance abused was marijuana and antipsychotic medication intake remained constant. Each time marijuana use at moderate levels began, there was exacerbation and deterioration. The author suggests that marijuana use is a special hazard to schizophrenic patients and that physicians should alert such high-risk patients to the possible untoward interaction between their illness and marijuana.