To understand how key relational factors lead to observed outcomes in mental health peer support.

This realist-informed qualitative review synthesised findings from 18 studies to develop programme theory relating to interpersonal contexts, linked outcomes and underlying mechanisms of change of mental health peer support.

Four databases were searched: PsycINFO, Embase, Medline, CINAHL.

All studies were evaluated for relevance and rigour for development of programme theory.

Qualitative data were extracted from 20 studies. A realist-informed synthesis identified repeating themes with context-mechanism-outcome configurations.

This identified five key contextual factors that together form the APPEAR framework (Accepting, Personalised Practice, Empowering, Available and Reciprocal). These contextual factors were found to interact to create the conditions for improved personal recovery outcomes in the domains of (1) self-acceptance, (2) confidence, (3) hopefulness, (4) self-expression, (5) relationships and (6) knowledge and skills.

The APPEAR framework offers an operational foundation for understanding interpersonal mental health peer support interventions.