Psychosis and cannabis abuse in The Gambia. A case-control study.

Cannabis abuse is a major public health problem in The Gambia and other parts of West Africa, and the rise in the incidence of psychotic illness reflects the increased background use of cannabis by the local population. A case-control study was performed to determine the association between psychosis end cannabis abuse in The Gambia and the importance of other risk factors. Out of 234 patients admitted to Campama Psychiatric Unit over 12 months, 210 (90%) were enrolled in a case-control study. Urine was tested for cannabinoid substances and 38% were positive compared with 12% of matched non-psychotic control subjects. Analysis of the matched pairs showed that a positive urinary cannabinoid test, cigarette smoking, alcohol consumption, travel to Europe and family history of mental illness were all significant risk factors for psychotic illness; Koranic education reduced the risk. There was a positive correlation among the psychotic patients between a positive urinary cannabinoid test and the use of alcohol, ataya tea and cigarette smoking; a family history of mental illness showed a negative correlation.