Role of cannabis in psychiatric disturbance

Clinical observation suggests that cannabis is implicated in some types of psychiatric disturbance. A record of admissions to two urban and four rural hospitals in Jamaica is examined along with details of individual cases. One-third of male admissions to the psychiatric hospital have used cannabis. Of 74 males admitted to another psychiatric service over a 12-month period, 29 had used cannabis. Ten of these patients were diagnosed as "ganja psychosis," and four others were classified as "marijuana-modified mania." At another psychiatric service, 54 of 223 admissions (24.2%) for functional psychosis presented with cannabis usage as a comtributory factor. These 54 patients included 14 and seven cases of hypomanic and depressive reactions, respectively. At three other rural general hospitals, psychiatric admissions for psychosis showed 11 of 51, seven of 18, and 39 of 75 patients, respectively, in whom cannabis was considered directly responsible. These findings lend support to the idea of causation of illness or modification of existing illness. The negative findings of controlled studies in the same country are not inconsistent. A suggested classification for adverse reactions to cannabis offered by one author is recommended, because it is in accord with common local clinical experience.