The primary objective of this clinical trial is to determine the clinical and cost-effectiveness of psychoeducation and emotional stabilisation (PES), together with eye movement desensitisation and reprocessing (EMDR) plus treatment-as-usual (TAU) in reducing symptoms of post-traumatic stress disorder (PTSD) among adults with intellectual disabilities compared with TAU. Secondary objectives include: (1) determining whether PES/EMDR plus TAU is superior to TAU in improving mental health problems and quality of life (QoL) among adults with intellectual disabilities who had a diagnosis of PTSD and (2) completing a process evaluation to examine intervention implementation and acceptability.

This is a two-arm parallel single-blind randomised controlled trial comparing PES-EMDR+TAU to TAU including an internal pilot phase. Outcome data will be captured prior to randomisation, and at 4 (after PES), 8 (after EMDR) and 14 months postrandomisation by masked assessors. 144 adults with intellectual disabilities with a diagnosis of PTSD will be allocated (1:1) randomly using minimisation from National Health Service (NHS) community and inpatients services for adults with intellectual disabilities in England. Participants are eligible to take part in this trial if: (1) they are aged 18 or older, but younger than 66, (2) have a Full Scale IQ

The primary outcome will be assessed using an intention-to-treat analysis. Baseline characteristics will be compared between arms to determine whether any potentially influential imbalance occurred. The primary outcome will be analysed by analysis of covariance, adjusting for baseline values of the outcome and any variables used in the randomisation process. Secondary outcomes will be analysed using linear or logistic regression models as appropriate reflecting the distribution of the outcome variable. The treatment effect will be estimated as an adjusted difference between sample means, presented with 95% CIs and p values. A complier average causal effect analysis will be considered should the data availability be sufficient to estimate the impact of non-compliance. A series of subgroup analyses on the primary outcomes will be considered considering differences in the Impact of Event Scale–Intellectual Disabilities scores at 14 months for (1) differing levels of general intellectual functioning and (2) PTSD versus complex PTSD.

This clinical trial was designed to allow for conclusions about whether PES/EMDR+TAU is efficacious in reducing symptoms of PTSD, relative to TAU, for adults with intellectual disabilities. A favourable ethical opinion has been received from an NHS ethics committee in the UK. The findings from this trial will be published within peer-reviewed journals and shared at national and international conferences. We will also aim to record and distribute podcasts detailing our findings together with our partners.

ISRCTN35167485.