(OR = 0.35, 95% CI: 0.03, 3.49). As 3 years is a relative short period of follow-up, long-term effects of cannabis use on mania outcomes could not be detected. The results suggest that cannabis use may affect population expression of manic symptoms (and subsequent risk to develop bipolar disorder [Regeer, E.J., Krabbendam, L., R, DE Graaf, Ten Have, M., Nolen, W.A., Van Os, J., 2006. A prospective study