Psychological Adjustment to Long-term (PAL) Physical Conditions: A Randomised Cross-over Feasibility Trial of a Self-guided App

This study is a two-arm, randomised controlled cross-over feasibility study with a nested, optional qualitative study. The intervention consists of a self-guided smartphone app (Orbi) based on cognitive behavioural therapy (CBT) principles, which is designed to support psychological adjustment in long-term physical conditions. Orbi is an app adaption of an existing, evidence-based web-based intervention COMPASS. The control condition consists of usual charity support (UCS) for the relevant long-term physical health conditions (LTCs). All charity support includes a helpline which can be accessed via telephone or email. The goal of this trial is to evaluate the feasibility of Orbi and the main questions it aims to answer are: 1. Is Orbi a feasible and acceptable intervention for individuals experiencing psychological distress related to LTCs? 2. Which aspects of the Orbi app and the trial enhance or diminish participants' experiences? Participants will: * Be randomised and each participant has an equal (50 %) chance of being assigned either to the Orbi+UCS group or to UCS group alone for 12 weeks. After 12 weeks, they will be crossed over to the alternate condition for another 12 weeks * Complete questionnaires to assess psychological distress and intervention engagement at baseline, 6 weeks, and 12 weeks. * A subset of participants will be invited to take part in a nested, optional semi-structured interviews to explore their experiences using Orbi and participating in the study.