Background: People with Parkinson's disease can experience psychological distress and have difficulties accessing face-to-face psychological support due to symptom burden and limited availability of psychological services. Digital options for psychological support can bridge this gap. We have developed an app based on acceptance and commitment therapy (ACT) to support people with Parkinson's to improve psychological wellbeing.

Aim: To assess the acceptability of the app and the feasibility of conducting a randomised controlled trial (RCT) to evaluate the effectiveness of using the app to improve wellbeing for people with Parkinson's.

Methods: We will conduct a parallel-group randomised controlled feasibility trial comparing a digital app based on ACT (intervention group) to usual care (waitlist control group). We will recruit 60 people with Parkinson's, 40 to the intervention group and 20 to the control group. Primary feasibility outcomes include recruitment and retention rate, intervention engagement and satisfaction. Secondary outcomes include measures of clinical effectiveness (anxiety and depression), quality of life and cost-effectiveness. Interviews will be conducted to assess acceptability of the app. Primary feasibility outcome data will be analysed descriptively and compared against pre-defined feasibility criteria. Secondary outcomes will be analysed based on an intention-to-treat principle, and a cost-consequence analysis will be used to estimate cost-effectiveness. Interviews will be analysed using a deductive thematic analysis based on the Theoretical Framework of Acceptability.

Discussion: This trial will provide data on the feasibility of conducting a full-scale RCT of the effectiveness and cost-effectiveness of the app to improve psychological wellbeing for people with Parkinson's disease.