Interpersonal and Intrapersonal Functions of Deliberate Self-Harm (DSH): A Psychometric Examination of the Inventory of Statements About Self-Injury (ISAS) Scale

Abstract

Deliberate self-harm (DSH), commonly defined as the intentional, direct and non-suicidal destruction of one's body, appears to be common across both clinical and non-clinical populations. A recently developed measure of functions of DSH, the Inventory of Statements About Self-Injury (ISAS), was examined to test its two-factor model within a sample of members of online social networks. The approach adopted was to fit data from the scale to the Rasch measurement model, which is increasingly used to develop and/or assess scales. Two hundred and one (n = 201) participants aged over 18 years of age, who had engaged in DSH in the last 12 months, were recruited from online social networks’ DSH peer support groups to complete an online survey. An exploratory factor analysis supported interpersonal and intrapersonal factors based on 13 function domains. Furthermore, both factors demonstrated satisfactory fit to the Rasch model. Some local dependency was detected, and when addressed, it impacted on the alpha coefficient level for intrapersonal factor. This study is the first independent psychometric investigation of ISAS, further supporting the scale authors’ psychometric evaluations. Additional validation across different DSH samples is recommended.