Rewards for Cannabis Abstinence-study

Summary

The goal of this clinical trial is to investigate the (cost-)effectiveness of contingency management (CM) compared with Cognitive Behavioural Therapy (CBT) for the treatment of cannabis use disorder (CUD) in youth (16-22 years).

The main questions it aims to answer are:

* What is the efficacy of 12 weeks outpatient CM versus CBT in youths with a CUD, in terms of cannabis abstinence during the intervention period?
* What is the long-term efficacy of CM versus CBT at 6- and 12-months follow-up (FU)?
* What is the cost-effectiveness of CM versus CBT at 12-months FU from a societal perspective?

Study hypotheses are:

1\. CM will result in more cannabis-abstinent days than CBT during the intervention; 2. CM is more effective and cost-effective than CBT at 12 months follow-up.

Eligible patients (n=154) will be randomly assigned to either 12 weeks of outpatient CM or CBT. Assessments are conducted by trained research-assistants at baseline, after 6, 12, 26 and 52 weeks, and twice-weekly during treatment and consist of questionnaires, a computer task and collection of urine samples. Primary endpoint is the number of biochemically verified cannabis abstinent days in the 12-week treatment period. Key secondary endpoint: Treatment response: 50% or more reduction in cannabis use days in the past 4 weeks, compared with baseline.

The primary outcome will be modelled in the intention-to-treat population in a (negative binomial) regression analysis with treatment group as independent variable and stratification variables as covariates.

Cost-effectiveness and cost-utility analysis (CEA; CUA) will be performed from a societal perspective. CEA: Treatment response is the central clinical endpoint for calculations of incremental costs per responder. CUA: Incremental costs per QALY (based on EuroQoL).

Conditions

• Cannabis Use Disorder

Interventions

BEHAVIORAL

Abstinence-focused Contingency Management (CM) - stand alone

Outpatient abstinence-focused contingency management (CM) as stand-alone treatment (12 weeks). Monetary incentives (vouchers) are provided for cannabis abstinence, based on twice-weekly rapid test urinalysis and an escalating reward scheme with bonuses. Urine samples are collected at the treatment centre during 15-minute sessions by a trained CM-practitioner. For each cannabis-negative urine, patients receive a monetary voucher starting at €5 and escalating to max. €35 after eight consecutive weeks of cannabis abstinence, with an additional €10 bonus after two consecutive cannabis-negative urines. The voucher-value is reset to €5 after a cannabis-positive urine test. Total earnings can be max. €675 for 12 weeks of consecutive cannabis abstinence (average: €8 p/day). Youths sign an agreement stating that vouchers must be spent on recovery-oriented goals.

BEHAVIORAL

Standard Outpatient Cognitive Behavioural Therapy (CBT)

CBT is the usual care first line treatment for CUD in youth, in the Netherlands. CBT for CUD is focused on learning cognitive, emotional, motivational and behavioral skills to reduce or cease cannabis use, and generally consists of 12 once-weekly 60-minute sessions and 'homework' exercise assignments, provided by a psychologist. Youths receive 12 weeks of outpatient usual care CBT consisting of once-weekly 60-minute sessions according to the standard CBT youth protocol by a trained psychologist. CBT-youths receive the same cannabis urine-testing procedures as CM-youths, but test results will not be disclosed to treatment staff or patient, and no rewards will be given for cannabis abstinence.

Sponsors & Collaborators

• Leiden University Medical Center

  collaborator OTHER

• Brijder Verslavingszorg

  collaborator UNKNOWN

• Antes

  collaborator UNKNOWN

• Novadic-Kentron

  collaborator UNKNOWN

• Amsterdam University of Applied Sciences

  collaborator OTHER

• Academisch Medisch Centrum - Universiteit van Amsterdam (AMC-UvA)

  collaborator OTHER

• Trimbos

  collaborator UNKNOWN

• Het Zwarte Gat

  collaborator UNKNOWN

• Parnassia Addiction Research Centre

  lead OTHER

Principal Investigators

• Renske Spijkerman, PhD · PARC

• Vincent Hendriks, Prof. dr. · PARC

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

NONE

Model

PARALLEL

Eligibility

Min Age

16 Years

Max Age

22 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2023-11-21

Primary Completion

2026-12-31

Completion

2027-09-30

Countries

• Netherlands

Study Locations