The People with Asperger syndrome and anxiety disorders (PAsSA) trial: a pilot multicentre, single-blind randomised trial of group cognitive–behavioural therapy Peter E. Langdon, Glynis H. Murphy, Lee Shepstone, Edward C.F. Wilson, David Fowler, David Heavens, Aida Malovic, Alexandra Russell, Alice Rose and Louise Mullineaux Background There is a growing interest in using cognitive–behavioural therapy (CBT) with people who have Asperger syndrome and comorbid mental health problems. Aims To examine whether modified group CBT for clinically significant anxiety in an Asperger syndrome population is feasible and likely to be efficacious. Method Using a randomised assessor-blind trial, 52 individuals with Asperger syndrome were randomised into a treatment arm or a waiting-list control arm. After 24 weeks, those in the waiting-list control arm received treatment, while those initially randomised to treatment were followed up for 24 weeks. Results The conversion rate for this trial was high (1.6:1), while attrition was 13%. After 24 weeks, there was no significant difference between those randomised to the treatment arm compared with those randomised to the waiting-list control arm on the primary outcome measure, the Hamilton Rating Scale for Anxiety. Conclusions Trials of psychological therapies with this population are feasible. Larger definitive trials are now needed. Declaration of interest None. Copyright and usage © The Royal College of Psychiatrists 2016. This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY) licence. Anxiety disorders and related symptomatology are commonly found among those with autistic spectrum disorders (ASDs), including Asperger syndrome. 1–7 A meta-analysis examining the effectiveness of cognitive–behavioural therapy (CBT) for anxiety disorders in children with ASDs reported that treatment had an effect size of d=1.19 for clinician-rated outcome measures, d=1.21 for parent-rated outcome measures and d=0.68 for child self- report outcome measures. 8 The literature about the treatment of mental health problems for adults with ASDs using CBT remains relatively sparse; there have been some case studies 9,10 and some small trials. 11–14 The aim of this trial was to collect data sufficient to inform the design of a definitive large-scale trial. The specific objectives included (a) assessing whether a CBT intervention is likely to be efficacious within a pilot, assessor-blind RCT with adults who have Asperger syndrome experiencing problems with anxiety, and (b) to gain participant views about taking part in therapy. Method Participants Fifty-two individuals, M age =35.9, s.d.=14.5, 48% women, were recruited and enrolled within the trial from Kent, South East London and Norfolk within the UK. Recruitment took place within the community from Asperger syndrome/autism teams, Asperger syn- drome user groups, such as Asperger East Anglia, the Kent Autistic Trust, Bridging the Gap, the Disability and Dyslexia Support Services at the University of Kent, intellectual disability teams, adult mental health teams, and through public advertisements. Participant flow throughout the trial is found in Fig. 1, and further demographic information can be found in Table 1. All participants were initially screened by research workers to determine eligibility to take part in the trial. The inclusion criteria were as follows: (a) participants fulfilled diagnostic criteria for Asperger syndrome, high-functioning autism or pervasive developmental disorder – not specified; diagnosis was confirmed by inspection of previous records, or the study team used the Autism Diagnostic Observation Schedule to confirm the diagnosis; (b) participants had clinically significant difficulties with anxiety as confirmed through the use of the Hamilton Rating Scale for Anxiety (HAM-A; score of >14 qualified inclusion); (c) participants were between 16 and 65 years of age; (d) full Scale IQ>70 on the Wechsler Abbreviated Scale of Intelligence. 15 The exclusion criteria were as follows: (a) participants with post-traumatic stress disorder, or anxiety related to substance misuse; (b) comorbid severe psychiatric disorders that impair capacity to consent to take part (e.g. florid symptoms of psychosis); and (c) current substance misuse such as alcohol or drugs. Design and randomisation This study was an assessor-blind randomised trial. Our full protocol has been published elsewhere. 16 Masked researchers enrolled participants and carried out the assessments. Even pairs of participants were allocated to the treatment arm (group CBT+ treatment as usual (TAU) for 24 weeks) or the waiting-list control arm (TAU for 24 weeks) using blocked randomisation with random even blocks, stratified by study site. The therapists at each research site contacted participants to inform them of their group allocation. All data were stored independently by the Norwich Clinical Trials 179 BJPsych Open (2016) 2, 179–186. doi: 10.1192/bjpo.bp.115.002527