A meta-analysis of the prevalence of different functions of non-suicidal self-injury

Background A broad variety of different functions can underlie acts of Non-suicidal self-injury (NSSI). Whilst research so far has identified many of the commonly reported functions, no reliable estimates of prevalence currently exist for these different NSSI functions. Understanding the prevalence of NSSI functions represents a key to better understanding the phenomenology of NSSI and addressing the differing needs of the NSSI population. We conducted a systematic review and meta-analysis of the prevalence of NSSI functions in community and clinical samples. Method A literature search of electronic databases PsycINFO, Medline, and Web of Science from date of inception to March 2017 was undertaken. A pre-specified framework for categorising different functions of NSSI was used to collate data from across studies. A random-effects meta-analysis of prevalence was then undertaken on these data. Results Intrapersonal functions (66–81%), and especially those concerning emotion regulation were most commonly reported by individuals who engage in NSSI (63–78%). Interpersonal functions (e.g., expressing distress) were less common (33–56%). Limitations The review was limited to English-language articles. Reviewed articles were inconsistent in their measurement of NSSI. Inconsistency within pooled prevalence estimates was high when moderators were not accounted for. Conclusions Findings indicate that intrapersonal functions of NSSI are most common and are present for the majority of participants. This finding supports dominant emotion-regulation models of NSSI, and the use of interventions that work to improve emotion-regulation ability. However, interpersonal functions remain endorsed by a substantial portion of participants.