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. Author manuscript; available in PMC: 2025 Mar 1.
Published in final edited form as: Drug Alcohol Depend. 2024 Jan 20;256:111096. doi: 10.1016/j.drugalcdep.2024.111096

Contingency Management is Associated with Positive Changes in Attitudes and Reductions in Cannabis Use Even After Discontinuation of Incentives among Non-Treatment Seeking Youth

Megan E Cooke 1, Sarah J Knoll 2, Joanna M Streck 2,3, Kevin Potter 2,3, Erin Lamberth 2, Natali Rychik 2, Jodi M Gilman 2,3, A Eden Evins 2,3, Randi M Schuster 2,3
PMCID: PMC10923125  NIHMSID: NIHMS1963636  PMID: 38277735

Abstract

Background:

It is important to identify interventions that reduce harm in youth not motivated to change their cannabis use. This study evaluated how short-duration contingency management (CM) impacts cannabis use attitudes and behavior after abstinence incentives are discontinued among non-treatment seeking youth.

Methods:

Participants (N=220) were randomized to 4 weeks of abstinence-based CM (CB-Abst; n=126) or monitoring (CB-Mon; n=94). Participants completed self-report and provided biochemical measures of cannabis exposure at baseline, end-of-intervention, and 4-week follow-up. Changes in self-reported cannabis use frequency (days/week; times/week) and biochemically verified creatinine-adjusted 11-nor-9-carboxy-tetrahydrocannabinol concentrations (CN-THCCOOH) were analyzed between groups from baseline to follow-up. In CB-Abst, cannabis use goals at end-of-intervention were described and changes in cannabis use at follow-up were explored by goals and cannabis use disorder (CUD) diagnosis.

Results:

There was a group by visit interaction on cannabis use (days: beta=0.93, p=0.005; times: beta=0.71, p<0.001; CN-THCCOOH: beta=0.26, p=0.004), with reductions at follow-up detected only in CB-Abst. Following 4 weeks of abstinence, 68.4% of CB-Abst participants wanted to reduce or abstain from cannabis use following completion of CM. Those in CB-Abst who set end-of-intervention reduction goals and were without CUD had greater decreases in cannabis use frequency at follow-up (Goals*time on days/week: beta=−2.27, p<0.001; CUD*time on times/week: beta=0.48, SE=0.24, t=2.01, p=0.048).

Conclusions:

Findings support the utility of brief incentivized abstinence for generating motivation to reduce cannabis use and behavior change even after incentives end. This study supports CM as a potentially viable harm reduction strategy for those not yet ready to quit.

Keywords: Contingency management, cannabis, adolescents, young adults, harm reduction, abstinence

Cannabis is the substance used most frequently among adolescents and young adults (Johnston et al., 2022; Schulenberg et al., 2021), yet most of those who use cannabis neither have a diagnosis of a cannabis use disorder (CUD) nor are seeking treatment (Substance Abuse and Mental Health Services Administration, 2019). While most young cannabis users are not currently seeking treatment, many may still experience adverse effects of their use, including those related to neurocognitive, interpersonal, psychiatric, and academic functioning (Barry et al., 2022; Copeland et al., 2022; Cyrus et al., 2021; Denissoff et al., 2022; Gobbi et al., 2019; Godin & Shehata, n.d.; Hengartner et al., 2020; Jacobus et al., 2009; Lorenzetti et al., 2020; Owens et al., 2022; Pacheco-Colón et al., 2019; Schaefer et al., 2021; Schmidt et al., 2020; Schweinsburg et al., 2008). Identifying early intervention strategies to promote healthy behavior change in young people with cannabis use who are not yet ready to quit has thus far been understudied.

Contingency management (CM) is a behavioral approach whereby incentives (e.g., cash, vouchers redeemable for goods and services) are provided contingent on evidence of behavior change; in the case of substance use, the target behavior is often biochemically-verified abstinence (Davis et al., 2016; Higgins et al., 1986, 1994). CM has demonstrated effectiveness in promoting abstinence from a variety of substances (Bolivar et al., 2021; Davis et al., 2016; Lussier et al., 2006; Prendergast et al., 2006), including cannabis (Kadden et al., 2007), among adults seeking treatment for or interested in changing their substance use behavior. In contrast, CM has largely been found to be ineffective in promoting cannabis abstinence alone or in tandem with other treatments among adolescents and young adults who use cannabis (Carroll et al., 2012; Kaminer et al., 2014; Killeen et al., 2012), albeit with a few exceptions (Stanger et al., 2009). This work has largely focused on youth who are treatment seeking and/or have a cannabis use disorder (CUD) diagnosis. Almost no research has explored the efficacy of CM as an early intervention strategy, including among non-treatment seeking adolescents and young adults.

In this secondary analysis, we sought to determine the impact of a brief CM intervention (i.e., 4 weeks) compared to non-contingent monitoring on biochemically-verified cannabis use behavior 4 weeks after discontinuation of abstinence incentives and longer-term intention to change cannabis use among a sample of non-treatment seeking adolescents with and without CUD.

1. Methods

1.1. Participants

Participants were drawn from two clinical trials investigating the effects of cannabis abstinence achieved via CM on cognition among non-treatment seeking adolescents and young adults (study 1 [pilot trial]: ages 18-25; study 2 [NIH-funded; NCT03276221]: ages 13-18). Eligible participants used cannabis at least weekly, used cannabis the week prior to enrollment, were not actively seeking treatment for cannabis use, had no immediate plans to reduce or discontinue cannabis use, were proficient in English, and were medically healthy.

1.2. Procedures

Procedures were approved by the Mass General Brigham Human Subjects Committee. Written informed consent (for those age 18 or older) or written participant assent and parent/guardian consent (for those under the age of 18) was obtained prior to conducting study procedures. Following informed consent procedures, participants completed a baseline visit (conducted over two visits for those enrolled in study 2). Participants were then randomized to 4 weeks of incentivized abstinence using CM (CB-Abst) or 4 weeks of monitoring with incentives provided non-contingent on abstinence (CB-Mon). Randomization was stratified by sex (male vs female), age (for study 2 only; 13–16 years vs ≥ 17 years), and average frequency of cannabis use (1 day per week vs ≥ 1 day per week). Participants completed 6 visits during the intervention phase of the study occurring at approximately day 3, 5, 7, 14, 21, and 28 post-randomization. CB-Abst participants were not required to maintain abstinence following completion of the CM intervention phase of the trial. Participants returned for a follow-up visit 2 to 4 weeks following the intervention phase (M=22.9 days, SD=9.5 days).

1.3. Contingency Management (CM) Protocol

The CM protocol has been previously described in detail (Cooke et al., 2021; Schuster et al., 2016, 2018, 2020). The CM procedure involved voucher-based incentives for 4 weeks of continuous, biochemically-verified cannabis abstinence. At baseline, all participants completed an abstinence contract with study staff which delineated the expected behavior changes across the 4-week intervention phase and schedule of payment if they were to be randomized to CB-Abst (Schuster et al., 2016). Following baseline, participants randomized to CB-Abst were asked to immediately cease cannabis use for 4 weeks, while those assigned to CB-Mon were not required to make any changes to their cannabis use habits. Participants randomized to CB-Abst who resumed cannabis use within the first week of abstinence (indicated by either self-report or biochemical verification) were given one chance to restart the abstinence protocol and remain in the study. Any additional use beyond the first week of abstinence resulted in study discontinuation. CB-Abst participants were reimbursed during the intervention period using a two-track incentive system, including static payments for attendance and escalating payments for biochemically-verified continuous cannabis abstinence. At the end of the 4 weeks of abstinence, CB-Abst participants were no longer required to abstain from cannabis use and were paid once more for attendance of a follow-up visit (Max payment for study 1: $545; Max payment for study 2: $420) (Schuster et al., 2016). CB-Mon were paid on an escalating schedule for attendance only (Max payment for study 1: $245; Max payment for study 2: $270). Both groups were reimbursed using reloadable debit cards through Clinical Trials Payer (CT Payer), a web-based platform that facilitates HIPAA and HITECH safe clinical trial payments. Payments were distributed on the day of the visit for attendance and upon receipt of the quantitative urinalysis results biochemically verifying abstinence (for CB-Abst; described below).

1.4. Biochemical Verification of Abstinence

Urine samples were collected at all study visits from all participants and shipped overnight to Dominion Diagnostics (North Kingstown, Rhode Island, USA) for quantitative assessment of cannabis metabolites. Biochemical urinalysis using liquid chromatography-tandem mass spectrometry (LC/MS/MS) was conducted for each sample to quantify 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH; ng/mL) concentrations. Assays had a limit of quantitation of 5 ng/mL and an upper limit of linearity of 500 ng/mL; serial dilutions were performed as necessary to obtain values within the linear range of the assay (i.e. 5 ng/mL–500 ng/mL). THCCOOH concentrations were normalized to creatinine levels (mg/dL), yielding a THCCOOH to creatinine ratio at each time point (CN-THCCOOH; ng/mg). CN-THCCOOH ratios between specimen pairs collected ≥48h apart were compared to an expected CN-THCCOOH ratio calculated using a statistical model to verify self-reported abstinence (Schwilke et al., 2011). This study used a 95% specificity threshold, allowing for a 2.5% false positive rate. For a more comprehensive evaluation and discussion of the use of this algorithm in this sample see Schuster et al., (2020). Once abstinence was verified (typically within 2-5 days following the study visit), appropriate remuneration was provided to study participants remotely on CT Payer cards and participants were notified.

1.5. Measures

Participants self-reported demographic information and cannabis use severity (Cannabis Use Disorder Identification Test (CUDIT; (Adamson et al., 2010) at baseline. A semi-structured interview with a trained member of study staff was completed to ascertain CUD diagnoses; study 1 used the Structured Clinical Interview for DSM-5 Disorders (SCID) (Williams et al., 2016) and study 2 used the Mini International Neuropsychiatric Interview (MINI; Sheehan et al., 2010). A Timeline Follow-Back (TLFB) of substance use frequency (days per week and times per day) (Robinson et al., 2014) was administered at every visit. The TLFB assessed substance use 90 days prior to enrollment at baseline and use since last visit at all subsequent visits. Cannabis use goal setting was assessed via a debriefing interview conducted at the end of the 4-week intervention phase of the study for those randomized to CB-Abst. Participants were asked the following questions: (1) “After today, what do you want your level of marijuana use to be?” [1; I want to remain completely abstinent from cannabis, 2; I want to resume using, but less than I did before I started the study, 3; I want to resume using at the same level as I did before I started the study, 4; I want to resume using, but more than I did before I started the study], and (2) “Moving forward, I see my level of cannabis use being…” [participant to free respond with intended number of days per week and times per day for cannabis use post-intervention].

1.6. Analytic Plan

The study sample included only those participants who provided follow-up data (80.9% of those enrolled). We compared participants in the CB-Abst who were and were not able to maintain incentivized abstinence for 4 weeks on baseline characteristics using t-tests and chi-square tests, as appropriate. Subsequent analyses only included those in CB-Abst who were able to maintain 4 weeks of continuous, incentivized abstinence. We compared baseline characteristics in the CB-Abst who were able to maintain 4 weeks of abstinence to the CB-Mon group using t-tests and chi-square tests, as appropriate.

The main goal of this study was to evaluate whether participating in 4 weeks of CM impacted change in cannabis use behavior after discontinuation of abstinence contingencies. The analyses for the current study focused on data collected at non-abstinent baseline, end-of-intervention, and follow-up. We analyzed self-reported days and times of cannabis use per week and CN-THCCOOH levels at the baseline and the follow-up visit using a linear mixed models for days per week, generalized linear mixed models with a penalized quasi-likelihood for times per week and CN-THCCOOH concentrations. Randomization group (CB-Mon vs CB-Abst), visit (baseline vs follow-up), and their interaction were included in the model. Follow-up period duration (in days) was included as a fixed effect covariate in all models. Days since last cannabis use was included as a fixed effect for analyses evaluating changes in CN-THCCOOH levels. Models included a participant-varying intercept. We used the same models when assessing changes in the CB-Abst group by baseline CUD diagnosis and reduction goals set at week 4 (set at end-of-intervention; coded as 0 = wanted to resume using at the same level or using more, 1 = wanted to use less or abstain from cannabis use following discontinuation of abstinence incentives). Model predictors and interactions were considered significant if the corresponding p-value was less than 0.05. All analyses were conducted using R v4.1.3.

2. Results

2.1. Study Sample and Participant Characteristics

Of participants randomized to CB-Abst (n=126), 81.7% (n=103) had 4 weeks of biochemically-verified continuous cannabis abstinence. Participants in CB-Abst who resumed cannabis use during the randomized phase, withdrew consent, or were lost to follow up (n=23) were younger (M=18.4, SD=1.9 vs. M=19.6, SD=2.1, p=0.02), had higher CUDIT scores (M=18.1, SD=5.4 vs. M=13.6, SD=5.5, p<0.001), used cannabis more frequently (M=5.8 days/week, SD=1.4 vs. M=4.5 days/week, SD=2.1, p=0.001), and had higher CN-THCCOOH levels at baseline (M=411.1 ng/mg, SD=358.6 vs M=167.2 ng/mg, SD=264.4, p=0.008) than CB-Abst participants who remained abstinent during the randomized phase of the study. Eight participants who were abstinent for the 4-week intervention did not attend the follow-up visit and were excluded from analyses, resulting in a final analyzable sample of 95 CB-Abst participants. Of those randomized to CB-Mon (n=94), 13.8% (n=13) did not complete the follow-up visit, resulting in a final analyzable sample of 81 CB-Mon participants. Table 1 shows descriptive characteristics of the final analyzed sample.

Table 1.

Participant characteristics by CB-Abst and CB-Mon groups at baseline

Measure CB-Abst (n=95) CB-Mon (n=81)
Demographics
Age* 19.7 (2.1) 19.0 (2.2)
Sex - female 44 (46.3%) 36 (44.4%)
Race
  African American, Black, or Haitian 11 (11.6%) 15 (18.1%)
Haitian
  American Indian/Alaska Native 0 (0%) 1 (1.2%)
  Asian 6 (6.3%) 8 (9.6%)
  Hawaiian or other Pacific Islander 0 (0%) 1 (1.2%)
  White 67 (70.5%) 45 (55.6%)
  More than one race 10 (10.5%) 9 (11.1%)
  Other 1 (1.1%) 2 (2.4%)
Ethnicity – Hispanic 7 (7.4%) 13 (16.0%)
Cannabis Use
Age of first cannabis use 15.4 (1.9) 15.2 (2.1)
Days per week of cannabis use 4.6 (2.1) 4.7 (2.2)
Times per week of cannabis use 10.1 (11.3) 9.4 (8.2)
CN-THCCOOH (ng/mg)* 127.2 (216.6) 240.6 (504.6)
CUDIT-R 13.6 (5.5) 13.8 (5.3)
CUD Diagnosis 47 (49.5%) 56 (67.5%)
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Note:

*

p < 0.05, Tables values depict Mean (SD) or N (column %). CN-THCCOOH = creatinine adjusted 11-nor-9-carboxy-Δ9-tetrahydrocannabinol concentration (ng/mg). CUD = cannabis use disorder, assessed via Mini International Neuropsychiatric Interview (MINI), Kiddie Schedule for Affective Disorders and Schizophrenia (KSADS), or Structured Clinical Interview for DSM-5 Disorders (SCID). CUDIT-R = Cannabis Use Disorders Identification Test-Revised.

2.2. Changes in Cannabis Use from Baseline to Follow-up

Compared to CB-Mon, CB-Abst reported a greater decrease in average frequency of weekly use from baseline to follow-up. There was an interaction between group (CB-Abst vs CB-Mon) and visit (non-abstinent baseline vs follow-up visit) on self-reported frequency of cannabis of use (days per week: beta=0.93, SE=0.33, t=2.85, p=0.005; times per week: beta=0.71, SE=0.13, t=5.40, p<0.001; see Figure 1, Table 2). CB-Mon did not decrease their cannabis use (days per week: BL, 4.6 (SD=2.2); F/U, 4.3 (SD=2.6); p=0.42; times per week: BL, 9.2 (SD=8.2); F/U, 8.9 (SD=9.7)) from baseline to follow-up. However, CB-Abst used an average of 1.2 (SD=2.4) days less per week (BL, 4.6 (SD=2.1); F/U, 3.4 (SD=2.4)) and 3.7 (SD=11.9) times less per week (BL, 9.9 (SD=11.0); F/U, 6.1 (SD=7.2)) 4 weeks after completing the CM intervention. Approximately half of participants in CB-Abst reported reducing the frequency of their cannabis use by at least 20% from baseline to follow-up -- 49.5% and 54.7% of participants reported a decrease in days and times of weekly use by >20%, respectively.

Figure 1. Change in Cannabis Use Frequency and CN-THCCOOH Levels Between CB-Abst and CB-Mon from Non-Abstinent Pre-Randomization Baseline to Post-Intervention Follow-Up.

Figure 1.

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Note: (A) group: beta=−0.02, SE=0.35, t=−0.04, p=0.96; visit: beta=−1.18, SE=0.22, t=−5.35, p<0.001; days since end of CM period: beta=0.01, SE=0.15, t=0.09, p=0.93; group by visit interaction: beta=0.93, SE=0.33, t=2.85, p=0.005. (B) group: beta=−0.18, SE=0.12, t=−1.42, p=0.16; visit: beta=−0.66, SE=0.10, t=−6.53, p<0.001; days since end of CM period: beta=0.08, SE=0.05, t=1.52, p=0.13; group by visit interaction: beta=0.71, SE=0.13, t=5.40, p<0.001. (C) group: beta = 0.05, SE=0.18, t=0.26, p=0.80; visit: beta=−0.32, SE = 0.08, t=−4.17, p<0.001; days since last cannabis use: beta=−5.43, SE=0.39, t=−14.02, p<0.001; days since end of CM period: beta=0.06, SE=0.09, t=0.67, p=0.51; group by visit interaction: beta=0.56, SE=0.08, t=7.06, p<0.001.

Table 2.

Changes in Cannabis Use from Baseline to Follow-up

Outcome
Days per week Times per week CN-THCCOOH
Group −0.02 (−0.71 - 0.67) −0.18 (−0.42 - 0.06) 0.05 (−0.30 - 0.40)
Visit −1.18** (−1.61- −0.75) −0.66** (−0.86 - −0.46) −0.32** (−0.48 - −0.16)
Group by Visit Interaction 0.93* (0.28 - 1.58) 0.71** (0.46 - 0.97) 0.56** (0.40 - 0.72)
Days since end of CM 0.01 (−0.28 - 0.30) 0.08 (−0.02 - 0.18) 0.06 (−0.12 - 0.24)
Days since last cannabis use N/A N/A −5.43** (−6.19 - −4.67)
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Note:

*

= p<0.05,

**

=p<0.001

There was also an interaction between group and visit on CN-THCCOOH concentrations (beta=0.56, SE=0.08, t=7.06, p<0.001; see Figure 1, Table 2). CN-THCCOOH concentrations decreased from baseline to follow-up in the CB-Abst group (raw values: BL, 168.8 (SD=268.7); F/U, 157.3 (SD=226.2); log values: BL, 4.63 (SD=1.60); F/U, 1.25 (SD=9.38)) but not the CB-Mon group (raw values: BL, 285.7 (SD=615.4); F/U, 263.0 (SD=694.7); log values: BL 4.73 (SD=1.52); F/U, 3.68 (SD=4.83)).

2.3. Goal Setting at End-of-Intervention and its Impact on Change in Cannabis Use from Baseline to Follow-up

CB-Abst, but not CB-Mon, participants set goals at the end of 4 weeks of incentivized abstinence for what they wanted their level of cannabis use to be once abstinence contingencies were discontinued. Five participants (5.3%) wanted to continue to abstain from cannabis use, 60 (63.1%) wanted to resume use but at a reduced level compared to baseline, 28 (29.5%) wanted to resume use at the same level compared to baseline, and 2 (2.1%) wanted to resume use at a higher level compared to baseline. Participants who wanted to reduce use set goals to reduce by an average of 2.3 days per week (SD = 1.4) and 5.8 times per week (SD = 5.3) compared to baseline frequency of cannabis use. Participants who set continued abstinence/reduction goals (n=65) had higher CUDIT scores (M=15.0, SD=5.5 vs. M=10.7, SD=4.4, p<0.001) and used cannabis on a greater number of days per week (M=5.0, SD=1.9 vs. M=3.8, SD=2.2, p=0.01) at baseline compared to those who did not want to change or wanted to increase their cannabis use (n=30).

Setting a reduction goal at the end of a brief period of CM was associated with less cannabis use at follow-up (Table 3). Those who set a goal to abstain or reduce use (vs. not) at the end of the 4-week CM period reported a greater reduction in days of cannabis use per week at follow-up (beta=−2.27, SE=0.47, t=−4.80, p<0.001; reduction goal: BL, 5.0(19); F/U, 3.1 (2.3); no reduction goal: BL, 3.8 (2.2); F/U, 4.15 (2.36)). There was also an interaction between goals and visit on CN-THCCOOH levels (beta=0.64, SE=0.10, t=6.60, p<0.001) such that those who set a reduction goal showed a greater decrease in CN-THCCOOH levels (log values: BL, 4.26 (1.45); F/U, 3.67 (2.14); raw values: BL, 148.3 (161.7); F/U, 154.3 (207.4) than those who did not set a reduction goal (log values: BL, 3.80 (1.94); F/U, 3.70 (1.90); raw values: BL, 213.1 (416.3); F/U, 163.7 (265.3). There was no interaction between goals and visit on times per week used (beta=−0.37, SE=0.21, t=−1.78, p=0.08; reduction goal: BL, 10.2 (10.5); F/U, 5.4 (7.3); no reduction goal: BL, 9.2 (12.2); F/U, 7.8 (6.9)).

Table 3.

Impact of Goal Setting on Change in Cannabis Use from Baseline to Follow-up

Outcome
Days per week Times per week CN-THCCOOH
Goal 1.14* (0.20 - 2.08) 0.05 (−0.30 - 0.40) −0.11 (−0.61 - 0.38)
Visit 0.37 (−0.40 - 1.13) −0.43* (−0.74 - −0.13) −0.48** (−0.61 - −0.35)
Goal by Visit Interaction −2.27** (−3.20 - −1.34) −0.37 (−0.79 - 0.04) 0.64** (0.45 - 0.83)
Days since end of CM −0.20 (−0.58 - 0.19) 0.02 (−0.14 - 0.18) 0.01 (−0.02 - 0.03)
Days since last cannabis use N/A N/A −0.13* (−0.24 - −0.02)
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Note:

*

= p<0.05,

**

=p<0.001

2.4. Impact of CUD Diagnosis on Change in Cannabis Use from Baseline to Follow-Up

We examined whether baseline CUD diagnosis impacted change in cannabis use (frequency and CN-THCCOOH levels) from baseline to follow-up among CB-Abst participants (CUD dx: n=47, no CUD dx: n=44, CUD dx data not collected: n=4). There was an interaction between CUD diagnosis and visit on number of times used per week (beta=0.48, SE=0.24, t=2.01, p=0.048, Table 4). Individuals who did not have a CUD diagnosis showed a slightly greater decrease in times used per week from baseline follow-up (BL, M=9.4, SD=10.6; F/U, M=4.6, SD=4.7) compared to individuals with a CUD diagnosis (BL, M=10.5, SD=11.8; F/U, M=7.4, SD=8.9). Conversely, there was an interaction between CUD diagnosis and visit on CN-THCCOOH levels (beta=−0.59, SE=0.15, t=−3.84, p=0.002, Table 4), which suggested that individuals with a CUD diagnosis showed a greater decrease in CN-THCCOOH levels from baseline follow-up (log values: BL, 4.5 (1.62), F/U, 4.13 (1.94); raw values: BL, M=244.0, SD=353.4; F/U, M=213.4, SD=280.3) compared to individuals without a CUD diagnosis (log values: BL, 3.75 (1.49), F/U, 3.2 (2.14); raw values: BL, M=94.7, SD=106.1; F/U, M=104.8, SD=144.7). There was no interaction between CUD diagnosis and visit on change in number of days used per week (beta=−0.03, SE=0.49, t=−0.07, p=0.95, Table 4).

Table 4.

Impact of CUD Diagnosis on Change in Cannabis Use from Baseline to Follow-up

Outcome
Days per week Times per week CN-THCCOOH
CUD Diagnosis 1.25* (0.25 - 2.25) 0.11 (−0.28 - 0.50) 0.85* (0.30 - 1.40)
Visit −1.27** (−1.95 - −0.59) −0.98** (−1.38 - −0.58) 0.30* (0.02 - 0.58)
CUD by Visit Interaction −0.03 (−0.99 - 0.92) 0.48* (0.01 - 0.95) −0.59** (−0.89 - −0.29)
Days since end of CM −0.53* (−0.97 - −0.09) −0.04 (−0.23 - 0.16) −0.13 (−0.40 - 0.15)
Days since last cannabis use N/A N/A −1.04 (−2.17 - 0.10)
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Note:

*

= p<0.05,

**

=p<0.001

3. Discussion

One criticism of CM is that it relies on tangible contingencies (e.g., money), which may be effective in the short-term during the incentivized period but may not impact an individual’s motivation to change once incentives end (Petry, 2010). Our data do not support this notion. We report that more than two thirds of adolescents and young adults set a goal of reducing their cannabis use after just 4 weeks of abstinence, despite reporting no interest in decreasing their use prior to starting the intervention. Importantly, these findings also provide preliminary support that a brief period of incentivized abstinence may also lead to subsequent behavior change. Participants who abstained from cannabis use for 4 weeks resumed use at a lower frequency than before they enrolled in the intervention compared to those who did not engage in incentivized abstinence during the intervention period. This suggests that even short-term CM may be useful in increasing motivation to engage in harm reduction. This short-term period of CM may provide a window of time in which adolescents and young adults with regular cannabis use may be able to self-reflect and increase motivation even among people who were previously not interested in change and those not yet cannabis dependent.

Not all studies that employ CM collect follow-up data after contingencies are removed (Davis et al., 2016). Studies with such follow-up data have reported mixed results (Sayegh et al., 2017). A meta-analysis of the durability of CM effectiveness found that across substances, CM had a medium effect on reduction of use by 3 months following discontinuation of abstinence contingencies, but not beyond 3 months (Sayegh et al., 2017). With regards to cannabis use specifically, CM produced a significant small effect on the reduction of cannabis use within 3 months and a trend towards an effect on outcomes measured between 3 to 6 months. However, participants in these studies were older (Mage=36.56) and treatment seeking. Our study is the first, to our knowledge, to report a decrease in cannabis use after contingencies have ended in non-treatment seeking frequent cannabis using youth. It is important to understand the impact of short-term abstinence on subsequent behavior as temporary pauses in cannabis use are common in young people. Prior research has demonstrated that such pauses when motivated by an attempt to increase tolerance to cannabis’ effects (i.e., tolerance breaks or T-breaks) may be associated with more hazardous cannabis use after abstinence in comparison to when motivated by other reasons (e.g., financial, lack of access, work-related, school-related, drug testing, school related, interpersonal; Ansell et al., 2023). This research combined with our current findings underscores the potential importance of an individual’s motivations as a factor in changes in cannabis use following periods of abstinence among adolescents and young adults.

Goal setting and CUD status moderated the effects of the 4-week abstinence period on subsequent cannabis use, suggesting that the effectiveness of this approach may not be uniform across groups of individuals. We show, for example, that while 4 weeks of CM was associated with reduced cannabis use in the full sample, reductions were particularly pronounced in those who set a goal to reduce their cannabis use at the end of the CM period. It is possible that those who set harm reduction goals may differ across baseline factors, as observed in the current study, and these baseline factors may drive differences in CM treatment effects. However, it is also plausible that the behavioral process of setting goals may itself potentiate the durability of CM’s effects. Goal setting is, in fact, one of the most common behavioral approaches for substance use (Black et al., 2020; Shoesmith et al., 2021, Fentress et al., 2021), as well as other disciplines (Ottenbacher & Cusick, 1990; Gollwitzer et al., 2006; Epton et al., 2017) and is postulated to improve clinical outcomes by improving self-efficacy, defining action-oriented strategies to achieve the desired outcome, and anticipating and planning for potential barriers (Locke & Lantham, 1990). Data on goal setting was not collected from the CB-Mon group in the present study which limited our ability to test any effects of goal setting separate from experiencing a period of abstinence. Future studies are warranted to specifically test whether collaborative goal setting at the end of a CM intervention or generally improves clinical outcomes.

Findings should be interpreted in the context of the following limitations. We only followed participants for up to 4 weeks following discontinuation of the incentivized abstinence period, therefore the persistence of the reported effects beyond this period is unknown. We also do not have follow-up data on participants randomized to CB-Abst who were unable to remain abstinent, which may limit our ability to generalize results to individuals with more severe cannabis use patterns who may be in most need of treatment. These individuals may still experience harm reduction benefits from even shorter duration CM, but this cannot be determined by the current study. Incentives were also provided once abstinence could be biochemically verified, which could take up to a week of processing. The inability to provide immediate reinforcement of abstinence may have weakened the efficacy of the CM intervention (Lussier et al., 2006). Finally, our study focused on adolescents and young adults who used cannabis frequently (using at least weekly) and were not interested in changing their use patterns or seeking treatment for their cannabis use. While these individuals represent most cannabis using youth, the findings reported here may not generalize to substances, ages, or individuals.

While barriers to implementing contingency-based interventions have been historically noted in clinical settings, relatively recent policy changes may pave the way for the expansion of CM as a clinical option. The Biden administration has prioritized expanded access to evidence-based treatment for substance use and has specifically identified the elimination of policy barriers to CM interventions and increased reimbursement for incentives through CM as viable solutions (The White House, Office of National Drug Control Policy, 2021). Findings from the current study support the short and longer-term efficacy of CM for cannabis abstinence and harm reduction and suggest CM may be a viable intervention approach for the large number of young people who use cannabis and are not yet ready to change their behavior.

Highlights.

  • Youth decreased cannabis use even after completion of contingency management (CM).

  • CM may increase intrinsic motivation to reduce cannabis use among youth.

  • CM may be a viable harm reduction strategy for youth not yet motivated to quit.

Funding Source:

This publication was made possible by support from NIH-NIDA [1K23DA042946, Schuster].

Footnotes

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Financial Disclosure: All authors have indicated they have no financial relationships relevant to this article to disclose.

Conflict of Interest: The authors have no conflicts of interest relevant to this article to disclose.

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