Separating within-person from between-person effects in the longitudinal co-occurrence of depression and different anxiety syndromes in youth

Cross-lagged panel models (CLPM) are often used to study anxiety-depression co-occurrence. However, the CLPM aggregates within- and between-person variance, which can lead to incorrect estimates. The latent curve model with structured residuals (LCM-SR) parses these sources of variance. We utilized the LCM-SR to examine prospective associations between anxiety (physical, social, separation) and depression. Youth (N = 680; M_age = 11.8; 55% female) completed measures of depression and anxiety every 3 months for 3 years (13 timepoints). The LCM-SR describing anxiety-depression co-occurrence fit well (RMSEA = 0.05, SRMR = 0.06). Depression predicted within-person change in social (b = 0.09), physical (b = 0.04), and separation anxiety (b = 0.06) over 13 timepoints. Separation anxiety predicted within-person change in depression (b = 0.08); social and physical anxiety did not. Findings advance knowledge of within-person development of anxiety-depression co-occurrence.