The aim of the present study was to determine whether psychopathic traits act as a predictor and/or moderator of the effectiveness of Multisystemic Therapy (MST).
The sample included N = 256 adolescents (188 boys and 68 girls) referred for conduct problems, randomized to MST or Treatment As Usual (TAU). The mean age was 16 years (SD = 1.31). Assessments were carried out before and immediately after treatment (6 months later). Three psychopathic traits (callous/unemotional traits, narcissism, and impulsiveness) were assessed with parent reports. Adolescents and parents were informants on externalizing problems.
MST was more effective than TAU in decreasing externalizing problems for the “lower callous/unemotional” and “lower narcissism” group, but not for the “high callous/unemotional” and “high narcissism” group (moderators). Impulsiveness was found to predict more post-treatment externalizing problems rated by adolescents (predictor), but not more post-treatment externalizing problems rated by parents.
These findings point out the clinical relevance of adequately assessing psychopathic traits in adolescents referred for treatment of antisocial behaviour, and identifying those adolescents who show high levels of these traits. It is important to tailor MST specifically to meet the needs of juveniles with high levels of callous/unemotional traits and high levels of narcissism to obtain the same level of effectiveness as with juveniles scoring lower on these traits.