["Journal of Intellectual Disability Research, Volume 70, Issue 5, Page 472-480, May 2026. ", "\nABSTRACT\n\nIntroduction\nUntil recently, no diagnostic instrument was available to classify posttraumatic stress disorder (PTSD) in individuals with severe or moderate intellectual disability (SID). This study investigates the Diagnostic Interview Trauma and Stressors–Severe Intellectual Disability (DITS‐SID), a caregiver‐administered interview corresponding with DSM‐5(TR) PTSD criteria for children ≤ 6 years. Interrater reliability and convergent and content validity were examined.\n\n\nMethods\nThe DITS‐SID, Aberrant Behavior Checklist (ABC) and Child and Adolescent Trauma Screener 3–6 (KJTS 3–6) were administered to relatives and professional caregivers of 97 adults with SID.\n\n\nResults\nInterrater reliability was good to excellent. Convergent validity was supported by correlations with ABC and KJTS 3–6 scores. Content validity appeared good as adults who met PTSD symptom criteria had, on average, higher interference scores, higher DITS‐SID atypical symptom scores and a greater number of experienced traumas and stressors. No association was found between meeting PTSD symptom criteria and PTSD criterion A.\n\n\nConclusion\nThe DITS‐SID appears feasible for classifying PTSD in adults with SID. Future research should evaluate its validity in children with SID.\n\n"]