Effectiveness of the Beat the Kick intervention in addressing substance abuse among adults with mild intellectual disabilities in the Netherlands: study protocol for an open-label, multicenter, superiority randomized controlled trial

People with mild intellectual disabilities (MID) are at elevated risk of substance-use problems. Beat the Kick is a motivation-focused, MID-adapted pre-treatment program. This trial aims to test whether Beat the Kick increases autonomous motivation to enter substance-use treatment versus care-as-usual (CAU), and to examine effects on substance use, satisfaction of basic psychological needs, treatment engagement, and acceptability.

Open-label, multicenter superiority randomized controlled trial in the Netherlands. We will recruit 138 adults (≥ 18 years) with MID or borderline intellectual functioning (intelligence quotient (IQ) 50-85 with adaptive limitations) and hazardous substance use (Alcohol Use Disorders Identification Test (AUDIT) ≤ 19 or Drug Use Disorders Identification Test (DUDIT) ≤ 24; ≥ 12 months) from six intellectual-disability care organizations. Recruitment will be conducted jointly by researchers from Tilburg University and care professionals at the participating organizations. In a Zelen pre-randomization design, eligible clients will be randomized 1:1 to Beat the Kick or CAU using a centralized computer-generated sequence with variable block sizes, stratified by addiction type (alcohol vs cannabis/other drugs). Tilburg researchers will obtain informed consent after allocation (intervention: consent for intervention + assessments; CAU: consent for assessments only). As an open-label trial, only the statistical analyst will remain blinded to allocation via A/B-coded datasets; the allocation key is held by an independent coordinator until primary analyses are complete. Assessments occur at T1 (pre), T2 (post), T3 (1 month), and T4 (6 months). Safety is monitored at T2-T4 through systematic adverse event (AE) and serious adverse event (SAE) recording, and serious events are reported to the Ethics Review Board within 24 h.

autonomous motivation (Treatment Self-Regulation Questionnaire; 15 items; 1-5 scale).

substance use ( Substance Use and Misuse in Intellectual Disability Questionnaire (SumID-Q) with AUDIT (0-40; ≥ 8 hazardous; ≥ 20 probable dependence) and DUDIT (0-44; ≥ 6 men/ ≥ 2 women hazardous; ≥ 25 probable dependence)), satisfaction and frustration of psychological needs (Basic Psychological Need Satisfaction and Frustration Scale - Intellectual Disability Version (BPNSFS-ID); 24 items; 1-5), treatment engagement (yes/no), and participant satisfaction. Primary analyses will use intention-to-treat linear mixed-effects models with fixed effects for group, time, and group × time, adjusting for the stratification variable.

This study evaluates a motivation-focused, MID-adapted program under routine conditions. Anticipated challenges (open-label bias, retention) are addressed through exclusive trainer allocation per arm, supportive scheduling, and caregiver involvement. If effective, Beat the Kick could be integrated into standard practice to improve readiness for treatment, substance-use outcomes, and overall well-being in adults with MID.

ISRCTN Registry, ISRCTN12571979. Registered on 11 June 2025. This trial was prospectively registered.