In this large UK-based cohort of 16-year-olds recent cannabis use, without apparent problems, was relatively common—slightly more so among girls than among boys. A smaller proportion (fewer than 5%) of the cohort reported cannabis problems and these were more common among boys compared to girls. Cannabis problems, compared to cannabis use without apparent problems, were associated more strongly with risk factors in earlier life, most notably social disadvantage, maternal substance use, maternal depression and early-onset persistent conduct problems. Almost a quarter of cannabis problems at age 16 appeared possibly attributable to early-onset persistent conduct problems and almost a fifth possibly attributable to maternal tobacco and cannabis use. While the effects of early-life factors were attenuated in models that also considered conduct problems (and vice versa), these effects remained strong, possibly reflecting independent influences. This evidence is the first of its kind from the United Kingdom, complementing previous studies in North America, Australasia and northern Europe 4–31.
