The effectiveness of an indicated prevention programme for substance use in individuals with mild intellectual disabilities and borderline intellectual functioning: results of a quasi-experimental study

Aims: To assess the effectiveness of Take it personal!, a prevention programme for individuals with mild intellectual disabilities and borderline intellectual functioning (MID-BIF) and substance use (SU). The prevention programme aims to reduce SU (alcohol, cannabis and illicit drugs) among experimental to problematic substance users. Design: A quasi-experimental design with two arms and a 3-month follow-up. Setting: Adolescents were recruited from 14 treatment centres in the Netherlands specialized in offering intra- and extramural care for people with MID-BIF and behavioural problems. Participants: Data were collected from 66 individuals with MID-BIF assigned either to the intervention condition (n = 34) or to the control condition (n = 32). Interventions: Take it personal! was designed to target four personality traits: sensation-seeking, impulsive behaviour, anxiety sensitivity and negative thinking. For each of these profiles, interventions were developed that were structurally the same but contained different personality-specific materials, games and exercises. The control group received care as usual. Measurements: Primary outcomes at 3-month follow-up were frequency of SU, severity of SU and binge drinking. Results: Results showed intervention effects for SU frequency (F_{(1, 50.43)} = 9.27, P = 0.004) and binge drinking (F_{(1, 48.02)} = 8.63, P = 0.005), but not for severity of SU (F_{(1, 42.09)} = 2.20, P = 0.145). Conclusions: A prevention programme to reduce substance use among experimental to problematic users with mild intellectual disabilities and borderline intellectual functioning helped participants to decrease substance use frequency and binge drinking.