Two cases of Acceptance and Commitment Therapy leading to rapid psychological improvement in people with intellectual disabilities Mark A. Oliver, Matthew Selman, Samuel Brice and Rebecca Alegbo Abstract Purpose – The purpose of this paper is to show that Acceptance and Commitment Therapy (ACT) may have utility with this client group in routine clinical practice. Design/methodology/approach – This uncontrolled double case study describes the targeting of ACT processes with people referred to a mental health service for people with intellectual disabilities because of distressing intrusive thoughts. It includes qualitative data to illustrate the opinions of the participants eight weeks after the end of therapy. Findings – Both clients described rapid relief from distress, with some additional untargeted benefits emerging too. The participants provided follow-up qualitative data in which they described how the therapy had helped them as well as areas where it had not. Research limitations/implications – This paper presents uncontrolled case studies selected from routine clinical practice. They were selected due to their similarity of outcome and will not represent the experience of every client treated this way. Practical implications – The practical implications are that a therapy often considered to rely on the use of metaphors and the manipulation of complex metacognitions may be useful for people with more limited verbal and cognitive ability if the therapy is adapted to meet their level of ability. Originality/value – There has been very little published on using ACT with an intellectual disabilities population. This paper has originality value in that it illustrates the application of the approach in routine clinical practice. Additionally, the qualitative follow-up allows the participants’ voices to be heard about their experience of this approach. Keywords Anxiety, Mindfulness, ACT, Acceptance and Commitment Therapy, Defusion, Relational frame theory Paper type Case study People with ID experience psychological distress at least as much as the typically developing population (Buckles et al., 2013). A recent review document prepared for the British Psychological Society (Beail, 2016) identified that while evidence is beginning to be gathered for a number of therapeutic orientations, the literature is not as yet clear which approach is best suited to which presentations in this population. The review notes that evidence continues to come predominantly from routine clinical practice and that clinicians in the field should be “aspirational and seek opportunities to expand our research efforts” (p. 206) and that innovations and adaptations should be evaluated as they are applied. One such innovation for this client group would be the application of Acceptance and Commitment Therapy (ACT). ACT (Hayes, Pistorello and Levin, 2012; Hayes, Strosahl and Wilson, 2012) is a “third wave” behavioural therapy (Hayes, 2004) that has attracted a growing number of studies over recent years (Hooper and Larsson, 2015). ACT is an explicitly behavioural psychotherapy, drawing upon operant principles of verbal language acquisition and rule governance for theoretical support, principally relational frame theory (RFT) (Hayes et al., 2001). The ability to relationally Received 16 April 2019 Revised 4 August 2019 Accepted 31 August 2019 There was no external funding involved in this paper. Mark A. Oliver is based at Northumberland Community Learning Disability Service (Psychological Services), Northumberland Tyne and Wear NHS Foundation Trust, Newcastle upon Tyne, UK. Matthew Selman is based at Northumberland Tyne and Wear NHS Foundation Trust, Newcastle upon Tyne, UK and Children and Young People’s Services, Tees Esk and Wear Valleys NHS Foundation Trust, Durham, UK. Samuel Brice is based at Northumberland Community Learning Disability Service (Psychological Services), Northumberland Tyne and Wear NHS Foundation Trust, Newcastle upon Tyne, UK and Institute of Neuroscience, Newcastle University, Newcastle Upon Tyne, UK. Rebecca Alegbo is based at Northumberland Tyne and Wear NHS Foundation Trust, Newcastle upon Tyne, UK and Norfolk and Suffolk NHS Foundation Trust, Norwich, UK. DOI 10.1108/AMHID-04-2019-0012 © Emerald Publishing Limited, ISSN 2044-1282 j ADVANCES IN MENTAL HEALTH AND INTELLECTUAL DISABILITIES