Participants will complete a seven-day combined CM with two sessions of brief Motivation Interviewing (MI) followed by standardized individual drug counseling.

Seven-day combined CM with two sessions of brief Motivation Interviewing (MI) followed by standardized individual drug counseling on cannabis use and relapse.

The Structured Clinical Interview for DSM-V (SCID-II) will be used to ascertain DSM-5 Axis 1 psychiatric and substance abuse diagnoses (First, et al., 2015) and specifically to determine presence/absence of DSM-5 Cannabis Use Disorder (CUD). The SCID-II interview for cannabis use will be administered at intake and weeks 4, 8, and 12 to measure changes in problematic cannabis use. The outcome will be the slope of change over study day in daily quantity of use and the percent use days per week. In addition, we will measure the percent of individuals who experienced a relapse throughout the study by week 12 (3 days of use weekly or 3 consecutive days of use).

The Time-Line Follow-Back Interview will also be used to assess cannabis, alcohol, other drugs and nicotine use in the previous ninety days, during the study and during follow-up. This is a reliable experimenter-administered assessment (Sobell and Sobell, 1992), which uses a calendar prompt to facilitate recall of drug use during a targeted period, and well-validated in alcohol and drug abuse treatment studies (Fals-Stewart et al., 2000). This questionnaire will be administered at intake and weekly. The outcome will be the slope of change over study day in daily quantity of use and the percent use days per week. In addition, we will measure the percent of individuals who experienced a relapse throughout the study by week 12 (3 days of use weekly or 3 consecutive days of use).

The Cannabis Use Disorder Identification Test-Revised (CUDIT) is an 8-item scale that will be used to quantify the severity of cannabis use over the past six-months (Adamson et al., 2010). This questionnaire will be administered at intake and weeks 4, 8, and 12. A summed score is used as an outcome where higher equals more cannabis-related problems.

A urine drug screen will be given at each visit during week 1 to reinforce using CM for cannabis abstinence and monitor progressive reduction in THC levels, and at each visit during the duration of the study to assess levels of THC for determination of the primary clinical outcome of cannabis relapse. The slope of change over weeks 1 through 12 in quantitative THC levels and metabolites will be the outcome measure.

The Cannabis Withdrawal Scale (Allsop et al., 2011):Participants will complete this questionnaire during weekly visits and during the EMA evening survey. The 19-item CWS has excellent reliability and has been validated in several previous cannabis abstinence, self-administration and treatment studies (Budney et al., 1999; Budney & Moore, 2002; Haney, 2002). Participants will indicate if they experienced these symptoms, the degree to which they experienced them (0=Not at all to 10=Extremely), and how much of an impact it had on their lives (0=No at all to 10=Extremely). A summed scores, where a higher score means more difficulty, will be used as the outcome. The slope of change in the number of symptoms endorsed weekly will be the secondary outcome measure.

The Marijuana Intoxication Assessment will be used to assess acute cannabis intoxication at each visit using a brief structured interview conducted by the trained research staff member. This 8-item will be measured at intake and during the first week. This is a screen to ensure compliance with study requirements.