Trauma-Specific Interventions for Individuals With Intellectual Disabilities: A Meta-Analysis of Single-Case Experiments

Individuals with intellectual disabilities are at increased risk of trauma exposure, yet trauma-related symptoms are often undertreated. Single-case experiments have been used to evaluate trauma-specific interventions for this population. This study aimed to estimate overall treatment effects and examine variability in effects across participants and studies. We conducted a systematic review and multilevel meta-analysis. We searched eight databases, followed by study selection, data extraction, quality assessment, and used a three-level model to estimate overall effects across repeated measurements, participants, and studies, as well as to examine moderators (age, sex, treatment type, symptoms, and risk of bias). We included data from 62 participants across 10 studies. Trauma-specific interventions significantly reduced symptoms, reflected in both immediate level change (β = −3.09, 95% CI [−4.56, −1.63], p < .001) and decreasing symptom trajectories over time (β = −.50, 95% CI [−0.71, −0.29], p < .001). Effects were stronger for individuals aged ≤18 years and for studies with high risk of bias. This synthesis provides evidence that trauma-specific interventions reduce trauma-related symptoms in individuals with intellectual disabilities. Youth appeared particularly amenable to current treatment models for psychological trauma. However, the evidence is limited by the small sample sizes and high risk of bias. More rigorous, well-reported, and geographically diverse studies are needed to reduce uncertainty about treatment options and establish reliable, generalizable conclusions.