Cannabis and brain function.

Current literature and practice experience has been reviewed to clarify what is known about the effects of cannabis on brain function, the risk that cannabis use may pose for young people during their adolescence, and risk factors within the individual or their environment that may predispose to long-term abuse and dependence. There is sound evidence that cannabis intoxication has an adverse effect on cognitive function and behaviour, and may, in vulnerable individuals, lead to a psychotic reaction. Regular use may have an adverse effect on learning, with possible mid- to long-term psychological and cognitive impairment. Heavy use may lead to emotional dependence with consequent social and psychological dysfunction. Intervention strategies must go beyond the conventional education and public health measures that appear to have been unsuccessful so far in influencing cannabis use in teenagers. Such strategies may more usefully aim at assessment of risk factors in individuals and groups for dependence on the drug, and the combined and cooperative intervention of parents, schools, health professionals and teenagers themselves.