Friendships and peer relationships and self-harm ideation and behaviour among young people: a systematic review and narrative synthesis.

Friendships and peer relationships have an important role in the experience of self-harm ideation and behaviour in young people, yet they typically remain overlooked. This systematic review and narrative synthesis explores the extant literature on this topic to identify important relationships between these constructs. We did a keyword search of peer-reviewed empirical articles relating to friendships and peer relationships and self-harm ideation and behaviour in young people (aged 11-25 years). We identified 90 articles with evidence primarily from adolescents aged 11-18 years, including mixed genders and a majority of White individuals. Findings highlight substantive relationships between the key constructs, showing that: characteristics of friends and peers, including their self-harm ideation and behaviour, relate to and predict ego self-harm ideation and behaviour; friends and peers are important sources of support; and evidence on causal mechanisms is scarce but highlights potential peer selection and influence processes. Studies of the friends and peers of young people with self-harm ideation and behaviour highlight that: friends' attitudes to self-harm and suicide influence their responses to peers with self-harm ideation and behaviour; and friends who are bereaved and friend supporters experience negative outcomes such as symptoms of depression, anxiety, PTSD, and grief, alongside difficult emotions. Despite substantial heterogeneity across samples, study designs, and definition or measurement of the primary constructs, this work presents an initial step in organising a complex literature on a crucially important topic, which can help to inform future research and evidence-based interventions.