Methods: A comprehensive search string and controlled vocabulary was developed in consultation with a reference librarian to identify all relevant papers published before March 2019 in six computerized bibliographic databases. Reference harvesting methods, such as using a university library search engine to find studies not indexed in the selected databases, were also used to identify articles. A study protocol was registered with PROSPERO that specified inclusion/exclusion criteria (including the omission of case studies without quantitatively measured outcomes). The presenting author screened 4,792 titles and abstracts with 68 full-text studies assessed for eligibility, and data was extracted and reviewed by two separate coders. All study decisions and discrepancies were resolved through consensus. Twenty studies were identified for inclusion through this search. Study quality was assessed using the ROBINS-I assessment tool.
Results: Eye Movement Desensitization Reprocessing (EMDR) was the most common (n=8) intervention used by clinicians and demonstrated success in the amelioration of trauma symptoms for individuals with IDD. A variety of instruments measured participants’ treatment progress and presence of trauma symptoms, with the Impact of Events Scale (IES) being the most common (n=7). Five of the seven studies which measured anxiety related to trauma found statistically significant reductions in symptoms by the end of treatment. Notably, in all three studies which incorporated control groups, the participants who received treatment for trauma did not perform statistically significantly better on outcome measures than the participants who received standard care. In fact, in two of these studies, the participants in the control groups showed more improvement than participants in the treatment groups. Small sample sizes and overall lack of control groups were methodological issues for most studies, thereby limiting generalizability of findings.
Conclusions and Implications: Trauma-informed interventions with modifications appear to be effective in alleviating PTSD symptoms, which challenges the assumption that cognitive impairments hinder the ability to process therapeutic tasks. However, few studies provided the information needed to conduct meta-analyses. Moreover, additional research is needed to determine if trauma-informed interventions for individuals with IDD are more effective in reducing trauma-related behaviors than treatment-as-usual, such as intensive behavior interventions (IBI) or traditional counseling methods.