Problematic substance use in adults with mild intellectual disabilities Mental and Behavioural Disorders
Conditions
Interventions
This study is a multicentre, two-arm, parallel-group, interventional randomised controlled trial (RCT), designed to evaluate the effectiveness of Beat the Kick, a structured motivational enhancement i
Sponsors
Tilburg University
Eligibility
Sex/Gender
All
Age
18 Years to 65 Years
Inclusion criteria
Inclusion criteria: Participants are eligible if they meet the following criteria: 1. Mild intellectual disabilities (MID) or borderline intellectual functioning (BIF): Defined by an IQ of 50–70 (MID) or 70–85 (BIF) combined with severe adaptive functioning limitations (defined by significant impairments in at least two of the following domains: conceptual, social, and practical skills, as outlined in the DSM-5). Both groups are collectively referred to as ‘individuals with MID’, reflecting their shared characteristics and support needs. In the Netherlands, these groups qualify for specialized mental health care and are often grouped in research, practice, and policy contexts. 2. Substance abuse: Hazardous alcohol or drug use that negatively impacts physical, psychological, interpersonal, or social well-being for a duration of at least 12 months. To focus the intervention on individuals with problematic use rather than severe substance use disorders, participants with indications of high-intensity or clinically complex use patterns will be excluded. This will be assessed using the Substance Use and Misuse in Intellectual Disability Questionnaire, which includes the Alcohol Use Disorders Identification Test (AUDIT) and the Drug Use Disorders Identification Test (DUDIT) to screen for substance use severity. Participants who exceed the established clinical thresholds for high-risk use (AUDIT > 19 or DUDIT > 24) will not be eligible to participate, as their level of use suggests the need for more intensive, specialized addiction care. 3. Lack of autonomous motivation: Participants must exhibit low autonomous motivation to change their substance use, as this is the primary target of the intervention. Autonomous motivation will be measured using the Treatment Self-Regulation Questionnaire (TSRQ), which assesses the extent to which individuals engage in change based on personal value, interest, or internal goals. This criterion ensures that the intervention is tested in individuals who are not yet ready or internally motivated to change, in line with the study’s aims. 4. Age: Participants must be 18 years or older to ensure legal competence for informed consent and appropriateness of intervention content. 5. Language proficiency: Participants must have sufficient Dutch language proficiency (minimum B1 level) to understand the intervention content, complete study measures, and engage in therapeutic conversations. This ensures the validity of assessments and meaningful participation. Added 23/01/2026: 6. Participants must not have received protocolled substance use treatment within the previous 18 months. For the purpose of this criterion, protocolled substance use treatment is defined as participation in a structured, manualised, or programme-based intervention with a clear treatment trajectory, including (but not limited to): 1. Motivational Interviewing (MI)–based programmes 2. Cognitive Behavioural Therapy (CBT) for substance use 3. Community Reinforcement Approach (CRA) Brief or incomplete treatment exposure (e.g. a single intake or orientation session without subsequent treatment sessions) is not considered sufficient to constitute protocolled treatment for the purpose of exclusion. Participants who received protocolled substance use treatment more than 18 months prior to baseline remain eligible. Prior treatment exposure will be systematically recorded and included as a potential moderator variable in the dataset. This criterion applies equally to participa
Exclusion criteria
Exclusion criteria: Participants will be excluded if any of the following apply: 1. Medication-related substance use: Individuals whose substance use is exclusively related to prescribed medications with potential for misuse (e.g., opioids, benzodiazepines, or ADHD medications like methylphenidate) will be excluded. This distinction is made in order to focus the intervention on non-medical substance misuse and to avoid medical confounds. 2. Lack of response or confusion: Individuals who are unable to provide meaningful verbal or non-verbal responses or who display significant confusion will be excluded. This ensures participants can engage with intervention content and assessments in a reliable and ethical manner. 3. Concurrent or planned substance use treatment: Individuals currently receiving, or planning to begin, other substance use interventions during the study period will be excluded to prevent treatment contamination and ensure internal validity of outcomes. 4. Unstable living situation: Homelessness or unstable housing will be grounds for exclusion due to the increased risk of dropout, relapse, and inability to guarantee follow-up. Stable living conditions are a known prerequisite for effective outpatient interventions. 5. Pregnancy: Pregnant individuals will be excluded due to ethical concerns and potential medical complications related to withdrawal, stress, and fetal risk. 6. Inability to give informed consent: Individuals who are legally restricted from consenting or who demonstrate cognitive impairments beyond the MID/BIF range will be excluded. However, when applicable, legal representatives may provide consent on their behalf in accordance with ethical guidelines, allowing participation when appropriate. This ensures ethical standards are upheld while maximizing inclusion.
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Autonomous motivation for substance use treatment measured using the Treatment Self-Regulation Questionnaire (TSRQ) at pre-treatment, post-treatment, and at 1- and 6-month follow-up | — |
Secondary
| Measure | Time frame |
|---|---|
| 1. Substance use levels measured using the Substance Use and Misuse in Intellectual Disability Questionnaire (SumID-Q) at pre-treatment, post-treatment, and at 1- and 6-month follow-up 2. Basic psychological need satisfaction measured using the Basic Psychological Need Satisfaction and Frustration Scale – Intellectual Disabilities (BPNSFS-ID) at pre-treatment, post-treatment, and at 1- and 6-month follow-up 3. Treatment engagement (defined as entering formal addiction treatment) measured via self-report and care records at 1- and 6-month follow-up 4. Participant satisfaction with the intervention measured using a structured feedback questionnaire at post-treatment | — |
Countries
Netherlands
Contacts
Public ContactRosemarie Gideonse
Outcome results
None listed