The Role of Parent–Child Attachment in the Association Between Loneliness and Self-Harm Thoughts and Behaviors in Daily Life

Adolescence is a critical period for self-harm thoughts and behaviors (SHTBs), and loneliness is an important risk factor. However, no research has investigated how loneliness is associated with adolescent SHTBs in real time and whether this association is influenced by parent–child attachment relationships, which correlate with both loneliness and SHTBs. We used experience-sampling methodology and self-report questionnaires to examine the role of loneliness and parent–child attachment in SHTBs in a general-population adolescent sample ( N = 1,602). Multilevel analyses provide evidence for loneliness as a short-term risk factor for self-harm thoughts and the emotion-regulation function of self-harm behaviors (i.e., downregulation of loneliness). The relationship between loneliness and SHTBs was stronger for participants with more insecure paternal and maternal attachment relationships. These results illuminate when (i.e., moments of loneliness) and why (i.e., loneliness downregulation) adolescents think about and engage in self-harm, offering critical guidance to clinicians and researchers.