Background: Despite progressive increasing of drug use or drug addiction particularly with cannabis in young people, knowledge is limited about their consequences on mental health in adulthood. In Fatick (Senegal), the mental health hospital “Dalal Xel” receives many young people who present psychiatric troubles necessitating a hospitalisation. Frequently, their history reveals use or abuse of cannabis joined sometimes with other drug. Method: From a study concerning period going from January 2010 to December 2013, the authors attempt to define the rate of cannabis users in the study’s population. Next, they seek to describe their social and familial characteristics, and the modality of cannabis use. Finally, they attempt to make correlations between use of cannabis and diagnostic delivered by doctors. Results: 9.13% of patients who are received during the study’s period report personal cannabis use. The middle delay between the first use of cannabis and the first apparition of psychiatric troubles is 4 years and 8 months. The diagnostic of acute delirious episode (BDA in French) is frequently evocated about a first episode or recidivism. Evolution respects classic report of 1/3 (good, bad and indeterminate). Schizophrenia is also evocated in non negligible proportion, particularly in early and prolonged use of cannabis. Conclusion: Psychopathological disorders are frequent among adolescents and young adults who are hospitalised in the psychiatric hospital of Fatick. Use of cannabis in long term seems to provide particularly psychosis.