Experiment II: In this randomized, placebo-controlled, double-blind study, 36 participants receive 7 days of THC (40-120 mg/day). On Day 8, 18 participants receive rimonabant dose determined in Experiment I to elicit cannabis withdrawal; 18 participants receive placebo rimonabant to evaluate spontaneous cannabis withdrawal. Cognitive, psychological, physiological and hormonal measures are monitored to determine onset, magnitude, and duration of THC intoxication and withdrawal and to correlate with THC and rimonabant pharmacokinetics. Changes in blood oxygen level-dependent (BOLD) signal are determined with five fMRI scans throughout the study. Eighteen non-drug-using controls undergo scanning and cognitive testing at similar intervals.