Changes in General and Specific Psychopathology Factors Over a Psychosocial Intervention.

OBJECTIVE: Recent research suggests that comorbidity among child and adolescent psychiatric symptoms can be explained by a single general psychopathology ('p') factor, as well as more specific factors summarizing clusters of symptoms. We investigated within- and between-person changes in the general and specific psychopathology factors over a psychosocial intervention.

METHOD: We ran a secondary analysis of the Systemic Therapy for At-Risk Teens study, a pragmatic randomized controlled trial that compared the effects of multisystemic therapy to management-as-usual for reducing antisocial behavior in 684 adolescents (82% male; 11-18 at baseline) over an 18-month period. The general p factor, as well as specific antisocial, attention, anxiety, and mood factors, were estimated from a symptom-level analysis of a set of narrow-band symptom scales measured repeatedly over the study. General and specific psychopathology factors were assessed for reliability, validity, and within- and between-person change using a parallel process multilevel growth model.

RESULTS: A revised bifactor model that included a general p factor and specific anxiety, mood, antisocial, and attention factors with cross-loadings fit the data best. While the factor structure was multidimensional, p accounted for most of the variance in total scores. The p, anxiety, and antisocial factors predicted within-person variation in external outcomes. p and antisocial factors showed within-person reductions, while anxiety showed within-person increases over time. Despite individual variation in baseline factor scores, adolescents showed similar rates of change.

CONCLUSION: The bifactor model is useful for teasing apart general and specific therapeutic changes which are conflated in standard analyses of symptom scores.

CLINICAL TRIAL REGISTRATION INFORMATION: START (Systemic Therapy for At Risk Teens): A National Randomised Controlled Trial to Evaluate Multisystemic Therapy in the UK Context. https://www.isrctn.com; ISRCTN77132214.