Page 136 - Post-traumatic stress disorder in adults with mild intellectual disability: Screening, assessment, and brief intensive EMDR therapy

Chapter 6
and 2 and in research by Mevissen et al. (2020a) and Nieuwenhuis et al.
(2019), PTSD is often not suspected in adults with MID-BIF. Although the
guidelines note that both the assessment and treatment of individuals with
(M)ID may require adaptations, it is not specified what these adaptations
should involve. Overall, the characteristics and needs of people with MID-
BIF are insufficiently addressed in the guidelines, which may contribute to
PTSD not being recognised and adequately treated within this population.
A final important factor for not recognising PTSD in adults with MID-BIF
is the limited availability of suitable diagnostic instruments until recently
(also see Hoogstad et al., 2025), which has complicated the accurate
identification and assessment of PTSD in adults with MID-BIF. The DITS-
ID, which was introduced in 2018, represented a first step for improving
the recognition of PTSD in adults with MID-BIF. In Study 1 (Chapter 2), we
examined the psychometric characteristics of the DITS-ID and found that
it was a reliable and valid instrument for classifying PTSD in adults with
MID-BIF, consistent with research conducted by Mevissen et al. (2020a).
However, the DITS-ID is not suitable for initial PTSD screening. At the start
of this research project, no screening instrument was available that had
been developed specifically for adults with MID-BIF and that aligned with the
DSM-5-TR criteria for PTSD. The lack of such a screener likely contributed to
not recognising PTSD in this group. As described in the General Introduction
(Chapter 1), it is essential that a PTSD screener for adults with MID-BIF is
both aligned with the current DSM-5-TR criteria for PTSD and adapted and
validated for adults with MID-BIF.
In Study 2 (Chapter 3), we evaluated the adult self-report and proxy
versions of the Trauma Screener–Intellectual Disability (TS-ID), which were
adapted from the Dutch Child and Adolescent Trauma Screener (Dutch
abbreviation KJTS; Kooij et al., 2025; CATS-2; Sachser et al., 2022), for use
in adults with MID-BIF. The self-report version of the TS-ID demonstrated
high internal consistency and excellent validity in distinguishing PTSD in
adults with MID-BIF. In contrast, while the proxy version also demonstrated
high internal consistency, it did not show validity in distinguishing PTSD.
This finding partly contrasts with research on the original KJTS (Kooij et
al., 2025), on which the TS-ID was based. In that study, the proxy version
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