Design Overview: This is a 10 week, open-label, prospective study, involving 10 volunteer participants with cannabis use disorder to test the feasibility and safety of using lorcaserin in addition to the feasibility, likability, and utility of a mobile sensor device in cannabis users. The study will be entirely outpatient Upon study entry, participants will begin clinic visits at the Substance Treatment and Research Service (STARS) clinic. All consented participants will receive a Fitbit charge HR mobile device in week 1 to wear for the entire study and receive lorcaserin beginning in week 2 for a total of 8 weeks (weeks 2-9). At the beginning of week 10 following discontinuation of lorcaserin, the participants will continue to wear the device for this final week following completion of the medication trial. All participants will visit the clinic twice weekly to provide urine toxicology on THC, report on adverse events, complete additional assessments (outlined below), and upload de-identified data from the device to a secure encrypted database. Study assessments will be collected at baseline, throughout the study, and 1 week following medication discontinuation. All participants will also receive medical management, a medication adherence focused psychosocial intervention that facilitates compliance with study medication and other study procedures, including adherence to wearing the device, and promotes abstinence from cannabis and other substances. Progressive voucher incentives will be provided for compliance with visit attendance and study procedures.