Are cannabis users exposed to other drug use opportunities? Investigation of high-risk drug exposure opportunities among young cannabis users in London.

In a study of young cannabis users attending further education colleges across London which specifically excluded young heroin users or injecting drug users, 35% were found to have been offered heroin, 36% had been present during heroin smoking, and 12% present at injecting. Factors associated with these exposure opportunities were investigated. The proportion of friends who use drugs other than cannabis was also considered, both as an indicator of risk in its own right and as a possible mechanism for high-risk drug exposure opportunities involving heroin and/or injecting. Alcohol variables and interactional problems perceived by the study subjects to be caused by their own drug use were found to be predictive of the involvement of friends in drug use other than cannabis and of exposure to heroin and injecting drug use. Non-cannabis illicit drug use among friends was also found to be associated with offers of heroin and with having been present during injecting drug use by others. Interpretations of these data are considered and the need for more detailed study with an area of increasing public policy significance is discussed.