Psychiatric effects of cannabis use.

That cannabis use may provoke mental disturbances is well known to Scandinavian psychiatrists today. A review of the psychiatric aspects of cannabis use is given, and the clinical signs of 70 cases of cannabis psychoses collected in Sweden are described. The bluntness and "amotivation" following chronic cannabis use are discussed. Anxiety reactions, flashbacks, dysphoric reactions and an abstinence syndrome are all sequels of cannabis use. Three risk groups begin to emerge: a) Young teenage cannabis users who lose some of their capacity to learn complex functions and who flee from reality to a world of dreams. With its sedative effect, cannabis could modify such emotions as anger and anxiety and slow down the liberation process of adolescence. b) Heavy daily users, often persons who cannot cope with depression or their life circumstances. c) Psychiatric patients whose resistance to relapses into psychotic reactions might be diminished according to the psychotropic effects of cannabis.