Cannabis Abuse and the Course of Recent-Onset Schizophrenic Disorders

TLDR

The study examined how cannabis abuse affects the symptomatic course of recent‑onset schizophrenia and related disorders. A one‑year prospective cohort study with monthly Brief Psychiatric Rating Scale assessments compared 24 cannabis‑abusing patients to 69 non‑abusers. Cannabis abuse, especially heavy use, was linked to earlier and more frequent psychotic relapses, preceded most first psychotic episodes, and was not confounded by other drugs, indicating it may act as a relapse stressor and premorbid precipitant.

Abstract

<h3>Objective:</h3> We sought to examine the relation between cannabis abuse and the symptomatic course of recent-onset schizophrenia and related disorders. <h3>Design:</h3> A prospective cohort study over a year using monthly Brief Psychiatric Rating Scale assessments. <h3>Participants:</h3> Cannabis-abusing patients (n=24) were compared with nonabusers (n=69). Eleven patients were mild and 13 were heavy cannabis-abusing patients. <h3>Results:</h3> Significantly more and earlier psychotic relapses occurred in the cannabis-abusing group (<i>P</i>=.03). This association became stronger when mild and heavy cannabis abuse were distinguished (<i>P</i>=.002). No confounding effect of other variables, eg, other street drugs, was found. In all but one patient, cannabis abuse preceded the onset of the first psychotic symptoms for at least 1 year. <h3>Conclusions:</h3> Cannabis abuse and particularly heavy abuse can be considered a stressor eliciting relapse in patients with schizophrenia and related disorders and possibly a premorbid precipitant.