Lorcaserin for Cannabis Use Disorder

The primary purpose of this study is to investigate the effect of lorcaserin on reductions in cannabis use and multiple constructs of impulsivity in outpatient treatment-seeking individuals with cannabis use disorder (CUD). Additionally, the investigators will make use of the technological application of ecological momentary assessments (EMA), to collect real-time data at key time intervals during the study on participants' use of cannabis and other substances in addition to measuring impulsive traits through self-initiated, fixed and random phone prompts. This will be a 13-week randomized, double-blind, placebo-controlled trial, with week 1 focused on baseline assessments of impulsivity (through EMA in vivo and at study visits), weeks 2- 3 of medication lead-in, and week 4 targeting a reduced cannabis use/quit day through week 13. The primary aims are to (1) Examine the effect of lorcaserin compared to placebo, on reductions in cannabis use among treatment-seeking outpatients with CUD, (2) Examine the effect of lorcaserin compared to placebo on behavioral and self-report measures of impulsivity among individuals with CUD during the medication lead-in phase (weeks 2-3). The secondary aim is to examine whether reductions in impulsivity (during weeks 2-3) mediates the effect of lorcaserin on cannabis use (during weeks 8-13), if the primary hypotheses are supported. Finally, the investigators will explore the effect of lorcaserin compared to placebo on (1) drop-out rates, (2) time to discontinuation from study, (3) treatment adherence, and (4) nicotine use.