Cannabis use disorders are an important public health problem in the United States, but there
are no effective medications available to treat these disorders. The investigators intend to
test a medication with interesting properties, nabilone, as a treatment for cannabis
dependence and to study the relationship of this treatment with the brain using functional
MRI brain scans. Nabilone and marijuana have similar effects upon behaviors and the human
body, suggesting that nabilone may decrease cannabis withdrawal symptoms while allowing
treatment-seeking patients to benefit from behavioral treatments when they are trying to stop
using cannabis. The investigators propose to assess the relationship of nabilone, when added
to behavioral treatment, on cannabis use patterns in cannabis-dependent patients. The
investigators also aim to determine the effects of nabilone on performance on
neuropsychological tests and to assess the correlation of neuropsychological performance to
brain changes using functional MRI brain scans. The investigators hypothesize that patients
receiving nabilone will reduce their use of cannabis more than patients receiving placebo
during this 10-week treatment trial.