Excessive cannabis use is associated with earlier age at onset in bipolar disorder

Lagerberg, T. V., Sundet, K. S., Aminoff, S. R., Berg, A. O., Ringen, P. A., Andreassen, O. A., & Melle, I. (2011). Excessive cannabis use is associated with earlier age at onset in bipolar disorder. European Archives of Psychiatry and Clinical Neuroscience, 261(6), 397-405. doi:10.1007/s00406-011-0188-4