Parents of children with autisma demonstrate elevated traumatic stress symptoms, but seldom receive diagnoses of post-traumatic stress disorder (PTSD) or complex PTSD. An accurate assessment of Criterion A is essential for a valid diagnosis of these disorders, yet it is uncertain whether Criterion A, as defined by the two primary international diagnostic systems (DSM-5-TR and ICD-11), yields consistent interrater reliability, when psychologists rely solely on self-report from these parents for assessing PTSD or complex PTSD.

This study aims to investigate interrater reliability across psychologists when assessing Criterion A events against the ICD-11 and DSM-5-TR.

Ten Australian psychologists rated parents’ self-reported traumatic events related to parenting, using the Life Events Checklist for DSM-5-TR and ICD-11 Criterion A. Data from 200 randomly selected parents of children, all meeting symptom thresholds for PTSD or complex PTSD, were analysed. Bootstrapping calculated kappa coefficients, differences between ICD-11 and DSM-5-TR criteria, and self-reports of threat/no threat, with 95% confidence intervals for these differences.

Interrater reliability varied from poor to moderate. The ICD-11 had significantly higher reliability than the DSM-5-TR for Criterion A (κdifference = 0.105, 95% CI 0.052–0.153, P < 0.001). The interrater reliability was lower when parents reported life threat, serious injury or death (κdifference = 0.096, 95% CI 0.019–0.176, P = 0.007).

This study highlights challenges in assessing PTSD and complex PTSD Criterion A in parents of children with autism, using DSM-5-TR and ICD-11 criteria with the Life Events Checklist, revealing less than adequate interrater reliability.