A Qualitative Study Exploring the Acceptability of Taking Part in a Large Multicentre RCT of Medication for Anxiety in Autistic Adults (the STRATA Trial).

Autistic adults experience significant physical and mental health inequities yet remain underrepresented in clinical research, with few randomised controlled trials to guide care. Randomised controlled trials (RCTs) of selective serotonin reuptake inhibitors (SSRIs) are limited, underpowered, and rarely focused on anxiety. Anticipating recruitment challenges in a large RCT ("STRATA") evaluating sertraline for anxiety in autistic adults, we embedded qualitative research to support recruitment, retention, and monitoring trial acceptability. We organised our findings into the theoretical framework of acceptability (TFA) constructs to assess the acceptability of trial design and delivery for autistic adults. We conducted 64 interviews with autistic adults at different trial stages. Data were analysed thematically and mapped to the seven TFA constructs. Participants considered involvement in a blinded medication RCT acceptable across the TFA domains, which they weighed differently when reflecting on anticipated versus experienced aspects of participation. STRATA was a low-burden, ethically sound, and methodologically coherent study for most participants, who reported minimal trade-offs, potential benefits, and self-efficacy in managing anxiety and research participation. Acceptability of trial participation is dynamic and multidimensional, which can be enhanced by meaningful involvement of autistic people throughout the research cycle, accessible participant information design, and responsive ongoing engagement.Lay AbstractAutistic adults often experience poorer physical and mental health than the general population. Yet they are rarely included in clinical research. There have been very few high-quality studies (RCTs) testing medications for anxiety in this group. Most existing studies are small and focus on other outcomes. They don't provide clear guidance for care. To help address this gap, the STRATA trial tested whether the medication sertraline (an SSRI) can reduce anxiety in autistic adults. Recruiting participants for such trials can be challenging. We included a qualitative study to better understand what helps or hinders people from joining and staying in the trial. We aimed to explore what aspects of the STRATA trial made it easier or more appealing for autistic adults to take part. We used a framework called the theoretical framework of acceptability (TFA) to define acceptability in this context. We interviewed 64 autistic adults at different stages of the trial, including 2 who chose not to take part. Most participants found the trial acceptable when assessed against the seven aspects of the TFA (i.e., how someone feels about taking part, how much effort is needed, whether taking part fits with a person's values, how well someone understands the study, what someone may have to give up, whether the study is likely to help, and how confident someone feels about taking part). In summary, they felt positive about taking part. They thought the study was ethical and easy to understand and believed it could benefit them. Many also felt more confident in managing their anxiety and contributing to research. STRATA is one of the largest studies of its kind; 318 autistic adults took part across the United Kingdom and Australia. The trial had a very high retention rate. Ninety-two per cent of participants stayed until the main outcome point, and 87% completed the full 52 weeks. How acceptable clinical trials like STRATA are may change during their course, and researchers need to be responsive. To do this well, researchers should involve autistic people meaningfully throughout the research process and from an early stage. Researchers also need to respect individual communication needs and provide clear and accessible information. These approaches were central to STRATA and supported by other studies.