Little is known about the association between trauma and intellectual disability in SMI patients.

To establish the prevalence of trauma and its association with intellectual functioning in SMI outpatients.

A cross-sectional study was conducted in two mental health trusts in the Netherlands. We used the Trauma Screening Questionnaire (TSQ) to screen for trauma and PTSD, and the Screener for Intelligence and Learning disabilities (SCIL) for suspected MID/BIF. Chi-square and t-tests were used to test differences in outcome over patient characteristics. Post-hoc analysis was used to investigate gender differences between patients with and without MID/BIF on trauma and sexual trauma.

Any trauma was found in 86% of 570 patients and 42% were suspected for PTSD. The SCIL suggested that 40% had Borderline Intellectual Functioning (BIF), half of whom were suspected of having Mild Intellectual Disability (MID). These patients had more traumatic experiences (1.89 in BIF, 1.75 in MID, against 1.41 in SCIL-negative patients). Female MID/BIF patients (61%) had experienced significantly more sexual abuse than male MID/BIF patients (23%).

Significantly more SMI outpatients who screened positive for MID/BIF reported having experienced traumatic events than those who screened negative. Rates of all trauma categories were significantly higher in the screen-positive group, who were also more likely to have PTSD. Sexual abuse occurred more in all females but the SCIL positive women are even more often victim. Clinical practice has to pay more attention to all of these issues, especially when they occur together in a single patient.