Adults (ages 18+) who would like to reduce their cannabis use (N=224) will be enrolled in an 8-week treatment program. All participants will receive counseling (1 goals session with a therapist followed by 7 weekly computerized cognitive-behavioral therapy sessions). Detailed cannabis assessments (biological and self-report) will be conducted throughout treatment and at 1-, 2-, and 3-months post-treatment completion. Daily electronic diaries will be administered via text message to record detailed logs of cannabis use quantity and frequency. Salivary samples will be collected (and video observed) daily throughout treatment to analyze for progesterone.

Eligible adolescents and emerging adults (ages 12-25) who have used cannabis in the past year will attend 1-2 laboratory visits. They will complete a series of interviews and self-report measures, including assessment of cannabis quantity and frequency, subjective effects of cannabis, and problems due to cannabis use. They will provide a urine sample for analysis of a THC metabolite and they will provide a blood sample for analysis of genes related to cytochrome P450 enzyme activity, which are thought to be associated with metabolism of THC.