Directionality of effects between non-suicidal self-injury and identity formation: A prospective study in adolescents

- Non-suicidal self-injury and identity formation are known to be correlated.
- The directionality of the association between these variables remains unknown.
- 380 high school students participated in a one-year, two-wave longitudinal design.
- Cross-lagged analyses indicated a bidirectional relation between the study variables.

The aim of the present 1-year longitudinal study was to investigate the directionality of association between NSSI and identity formation. We also explored if identity synthesis and identity confusion differed among the control, cessation, onset, and maintenance NSSI groups over a period of one year. We collected data on NSSI and identity from 380 high school students (Mean age = 14.3 years; SD = 1.68; range 12 to 19 years; 52.4% females) using self-report questionnaires at two measurement waves separated by a one-year period. The lifetime prevalence of NSSI at Time 1 was 14.2% and the 12-month prevalence of NSSI at Time 2 was 7.7%. We performed cross-lagged analyses using structural equation modelling techniques to investigate the directionality of effects. Our findings suggest that the associations between NSSI and identity synthesis and confusion are likely to be bi-directional. Mean differences in identity synthesis and confusion were also observed among control, cessation, onset, and maintenance NSSI groups. Clinical implications of these findings are discussed.