Understanding the subtypes of non-suicidal self-injury: A new conceptual framework based on a systematic review.

Non-suicidal self-injury (NSSI) is a significant public health problem, but there is no consistent evidence of its risk factors. One possibility is that there are subtypes NSSI that have different risk factors and clinical symptoms. In this review we evaluated the evidence of subtypes to determine if there were consistent subtypes of NSSI that emerged across studies. Four databases (Medline; Embase; PsycINFO; Web of Science) were searched to identify studies that used data-driven approaches and were published before November 9, 2022. There were 21 studies with 23 unique samples for review. Most of the included studies used NSSI symptoms or personal characteristics as the subtyping indicators, revealing 2-5 subtypes of NSSI. Variations in subtyping indicators, sample characteristics, and statistical methods may have contributed to the inconsistent number and characteristics of subtypes across studies. A new conceptual framework is proposed to integrate these diverse findings, highlighting the important roles of NSSI function and psychological pain in differentiating NSSI subtypes. This framework sheds light on the differences among self-injurers and offers insights for future endeavors to address the complexities of NSSI.