The higher prevalence of cannabis abuse or dependence in patients at high risk of schizophrenia, in patients with first psychotic episode, and during the course of schizophrenia patients with schizophrenia, compared with general population is well established. The reasons remain unclear and include familial vulnerability to drug use disorders, psychotomimetic effects induced by cannabis use, or personality traits. We have studied some aspects regarding vulnerability factors to cannabis use disorders in patients with schizophrenia: 1) We found that neurological soft signs scores were significantly higher in patients with cannabis dependence only, compared to healthy subjects, in particular regarding motor coordination and sensory integration 2) We found that the mean scores for impulsivity and sensation seeking were higher in a group of schizophrenia patients with lifetime cannabis abuse or dependence than in a group of schizophrenia patients without cannabis abuse or dependence 3) We assessed the role of individual sensitivity to the psychotogenic effect of cannabis among male patients with schizophrenia, and found that the first psychotic episode occurred 2.6 years earlier in cannabis-sensitive patients compared to non cannabis-sensitive patients. A specific excess of familial history of psychotic disorder was found in these patients 4) We found that the pattern of substance use disorders found in a group of Moroccan patients with schizophrenia was different from those found in previous studies from North America or Europe, suggesting that substance use disorders could be influenced by socio-cultural context and by the availability of cannabis.
Influence of cannabis use on the onset and the course of psychotic disorders