Page 131 - Post-traumatic stress disorder in adults with mild intellectual disability: Screening, assessment, and brief intensive EMDR therapy

General discussion
The studies presented in this dissertation aimed to improve the identification,
diagnostic assessment and treatment of post-traumatic stress disorder
(PTSD) in adults with mild intellectual disability (MID) or borderline
intellectual functioning (BIF). Adults with MID-BIF are at a higher risk of
developing PTSD than those in the general population (Mason-Roberts et
al., 2018; Mevissen et al., 2020a). However, PTSD is often not recognised
in these individuals (Mevissen et al., 2020a; Nieuwenhuis et al., 2019). This
may be partly explained by the limited availability of suitable diagnostic
instruments until recently (Hoogstad et al., 2025), which has complicated
the accurate identification and assessment of PTSD in these individuals.
Once diagnosed, it is important that individuals with MID-BIF receive PTSD
treatment, because untreated PTSD can have serious consequences
(Benedict et al., 2020; Davis et al., 2022; Gibson et al., 2020). Although
the number of treatment studies is growing in individuals with MID-BIF,
especially on eye movement desensitisation and reprocessing (EMDR)
therapy (for example, Byrne et al., 2022; Penninx et al., 2021; Verhagen et
al., 2023), there was still limited evidence at the start of our study regarding
the effectiveness of EMDR therapy in adults with MID-BIF and severe
behavioural problems. Behavioural problems could make EMDR therapy
more difficult to initiate or maintain, which underscores the importance
of examining whether EMDR therapy is feasible and potentially effective
in individuals with MID-BIF and behavioural problems. Research among
individuals in the general population shows that intensive trauma-focused
treatment is particularly effective, as it leads to a relatively fast reduction
in PTSD symptoms and low dropout rates (for example, Dell et al., 2023;
Gahnfelt et al., 2025; Hoppen et al., 2023; Oprel et al., 2021; Wachen
et al., 2019). Until recently, no studies had explored the effectiveness of
intensive treatment formats for adults with MID-BIF and severe behavioural
problems or how these individuals experience such intensive treatment.
To address the gaps in diagnostic assessment and treatment, this
dissertation had the following four objectives. First, to further examine the
psychometric properties of the adult version of the Diagnostic Interview
Trauma and Stressors – Intellectual Disability (DITS-ID-adults). Second, to
develop and evaluate a PTSD screener for adults with MID-BIF. Third, to
investigate the effectiveness of brief intensive EMDR therapy with rotating
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