Characteristics of adolescent boys who have displayed harmful sexual behaviour (HSB) against children of younger or equal age

Background: Adolescents who have displayed harmful sexual behaviour (HSB) are often described as a heterogeneous population, but different offender-, offense-, or victim-based typologies have been proposed. Two common typologies are based on the victim's age and/or on offender-victim age discrepancies. Methods: Using data from a Norwegian clinical sample, we aimed to investigate the characteristics of two subgroups of adolescents: those with younger/child victims (HSB-C) and peer victims (HSB-P). The sample was collected from a public child and adolescent psychiatry outpatient clinic. N=54 boys, mean age 14.1 (younger age: HSB-C, n=30, equal age: HSB-P, n=24). Based on patient records, all patient registries within the sample were reviewed retrospectively. The data were analysed in R with different statistical tests (e.g. N-1 chi-square test, Fisher's exact test). Results: After adjusting the p values for multiple comparisons, none of the test statistics showed significant results. Based on the magnitude of the effect-size estimates, the following tendencies and potential meaningful differences emerged: more adolescents in the HSB-C group had experienced their own trauma early (V=0.42), had more than one victim (V=0.32), and had displayed repeated HSB (V=0.27), and their caregivers required extensive interventions (V=0.20). More adolescents in the HSB-P group had cognitive abilities in the normal/high range (V=0.32), and their caregivers more often had difficulties acknowledging the need for support and treatment (V=0.20). Conclusions: The nonsignificant differences between the subgroups, despite some strong and moderate effects, bring about a discussion on the utility of using "victim age" in combination with the "offender-victim age differences" as the sole classification criterion for adolescents who have displayed HSB. The heterogeneity of the adolescent HSB population and lack of reliable information on more homogenous subgroups dynamics will remain challenges for clinicians and other practitioners needing a broad assessment and intervention focus.