In this pilot study, subjects will receive either nabilone or placebo in addition to medical management (MM) over a 10-week treatment period. Subjects' responses to neuropsychological testing carried out while the subject is receiving fMRI scans at 3 time points: at baseline, 4 weeks, and 10 weeks. Following treatment completion, subjects will have a follow-up visit at 14 weeks. This pilot study will evaluate the feasibility of nabilone treatment for cannabis dependence and will establish effect sizes for a larger trial in which subjects will receive high-dose nabilone, low-dose nabilone, or placebo in addition to MM.