Improving CommonGround, an Online Peer Support Intervention for People Living With Long-Term Physical Health Conditions and Subthreshold Depression: Theory of Change-Informed Qualitative Study.

People living with long-term physical health conditions who are also experiencing subthreshold depression are at risk of developing major depression. In partnership with lived experience experts, clinicians, and software developers, we co-designed CommonGround, an online peer support and psychoeducation platform. CommonGround's Theory of Change (ToC) was also conceptualized to outline the intermediate outcomes (and associated indicators of whether such outcomes are achieved) needed to improve the mental health of the target population. This qualitative study, informed by the ToC, aimed to exam