Background: Diagnostic manuals provide a strict definition of the PTSD gate criterion. Research on the adequacy of this definition in people with intellectual disabilities is lacking. This study aims to test the adequacy of the gate criterion for this population. Method: Forty-nine adults with mild to moderate intellectual disabilities and 43 caregivers were questioned. Traumatic events included in the gate criterion definition and adverse events going beyond it were assessed. It was tested whether adverse events affect symptoms of PTSD additionally to traumatic events. Results: The current data showed ambiguous findings in self- and informant report. Informant data suggested an additional impact of adverse events on PTSD symptoms. Self-report data suggested the contrary. Conclusion: Adverse events seem to have an impact on externalizing behavioural symptoms, such as hyperarousal. Self-report assessment of more specific, intrapsychic PTSD symptoms, such as intrusions and avoidance, should be addressed in future studies.