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

Objective: Recent research suggests that comorbidity in child and adolescent psychiatric symptoms can be summarized by a single latent dimension known as the p factor and more specific factors summarizing clusters of symptoms. This study investigated within- and between-person changes in general and specific psychopathology factors over a psychosocial intervention.

Method: A secondary analysis was conducted of the Systemic Therapy for At-Risk Teens study, a pragmatic randomized controlled trial that compared the effects of multisystemic therapy with those of management as usual for decreasing antisocial behavior in 684 adolescents (82% boys; 11-18 years old at baseline) over an 18-month period. The general p factor and specific antisocial, attention, anxiety, and mood factors were estimated from a symptom-level analysis of a set of narrowband symptom scales measured repeatedly during 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 bi-factor model that included a general p factor and specific anxiety, mood, antisocial, and attention factors with cross-loadings fit the data best. Although the factor structure was multidimensional, the p factor accounted for most of the variance in total scores. The p factor, anxiety, and antisocial factors predicted within-person variation in external outcomes. Furthermore, the p factor and antisocial factors showed within-person declines, whereas anxiety showed within-person increases, over time. Despite individual variation in baseline factor scores, adolescents showed similar rates of change.

Conclusion: The bi-factor model is useful for teasing apart general and specific therapeutic changes that 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; http://www.isrctn.com; ISRCTN77132214.