Links between cannabis and schizophrenic disorders are ages old. Cannabis has effects that are close to the symptoms of schizophrenia. Abuse and dependence are more frequent in schizophrenic population than in general population. This consumption is a gravity factor in terms of prognosis. It accelerates the first psychotic decompensations. Studies by cohorts of experts allow for the affirmation that cannabis is a risk factor in schizophrenic disorders, with an effect dose and depending, above all in the case of consumption before the age of 15. This observation is in line with the greatest diffusion of cannabinoid receivers in the encephalon of schizophrenic subjects and their role in cerebral maturity during puberty.