The goal of this study is to disentangle relationships between acute cannabis use and withdrawal on proximal depression and suicide risk and recovery in adolescents ages 12-18 years by incorporating time-varying patterns of substance use, mood, and SI. This project aims to guide the development of scalable, individualized, accessible, and affordable interventions aimed to reduce depression and suicide risk among adolescents.

We will recruit 200 community-based adolescents, ages 12-18 years, with daily or near daily cannabis use and current depression symptoms. Participants will be enrolled in a 10-week, 3-phased, mixed-methods protocol. All participants will complete a 2 week baseline phase (Phase 1) involving real-time, ambulatory smartphone monitoring (ecological momentary assessment; EMA) during which they will use cannabis per usual to quantify the temporal relationship between use and mood and SI, and the within- (e.g., concurrent other substance use, social context of use) and between-subject factors (e.g., severity of cannabis use, depression and SI) that moderate these linkages. We will work with participants schedule to ensure that the start of this 2-week baseline phase coincides with when they do not anticipate any major deviations from their typical pattern of cannabis use (e.g., family vacation, exam week). After the baseline phase, participants will be scheduled for the randomization component of the study, which will employ a 2-arm, within-subject, parallel group design to examine the effects of short- and longer-term cannabis withdrawal across 8 weeks of cannabis abstinence on depression and SI. Participants will be randomized to 8 weeks of abstinence with contingency management (CB-Abst; n=100) or non-contingent monitoring with no abstinence requirement (CBMon; n=100). Randomization will occur in a 1:1 ratio in blocks of 6 based on a computerized scheme developed by the study statistician. Randomization will be stratified by age, sex, and depression severity. A key aspect of the approach is that the 8-week period is long enough to observe true changes due to cannabis discontinuation, separate from effects of cannabis withdrawal, and residual cannabinoid exposure. Both groups will complete 1-week of EMA in weeks 1 (Phase 2) and 8 (Phase 3) of the randomized study period. In addition to the 3 waves of smartphone, EMA data collection, participants will complete 12 study visits across ~10 weeks. Visits will entail collection of urine samples for verification of self-reported use and abstinence verification (for CB-Abst during the randomization phase), as well as brief questionnaires and interviews on interim substance use, craving, withdrawal, mood symptoms, and SI.

Inclusion Criteria:

• Ages 12-18;
• Current daily or near daily cannabis use (i.e., use ≥ 4 days per week on average; Timeline Followback);
• Score ≥ 5 on PHQ-9;
• Access to an internet-capable smartphone (iOS or Android);
• Provision of at least 1 collateral contact for risk monitoring;
• Provision of informed assent (or consent if 18 years or older) and parent/guardian consent if <age 18;
• Greater than 50% response rate to EMA prompts during the first EMA phase;
• No immediate plan to discontinue cannabis use in the next 3 months;
• Positive toxicology result for cannabis on baseline urinalysis.

Exclusion Criteria:

• Any factor that impairs ability to comprehend and effectively participate, including acute intoxication at time of consent;
• Cannabis use >4 times/day on average (to maximize likelihood of capturing mood and SI during non-use times);
• Inability to speak/write English fluently;
• Gross cognitive impairment, for example due to florid psychosis, intellectual disability, developmental delay, or neurodegenerative disease;
• Current epilepsy diagnosis;
• Individuals who are under the legal protection of the government or state (wards of the state);
• Response of "No" to the knowledge check question regarding EMA suicidality response time;
• Inability to wear Fitbit device.

As outlined in the approved Data Management and Sharing Plan, IPD will be deposited in the NIMH Data Archive. This is a free data repository open to qualified researchers from all mental health and other research communities to share, archive, cite, access, and explore research data. Clinical data necessary to validate and replicate research findings, including questionnaires, interviews, ecological momentary assessment data, urine drug test results, and Fitbit recordings, will be shared.

Scientific data will be available one year after the grant end date specified on the first Notice of Award. Scientific data included in published manuscripts will be made available at the time of publication. Scientific data and the code/software/tools used to development the published or submitted dataset will be shared at the time of data submission or publication and maintained for no shorter than five years.

Data access will be controlled. In order to access shared data, qualified researchers will be required to complete a data use certification and receive approval from NDA Data Access Committee.