An emerging literature challenges traditional dimensional approaches to the study of psychopathology, bolstering evidence of a general (P) factor underlying symptomology across the internalizing and externalizing broad-band domains (Caspi et al., 2014). However, important developmental considerations necessitate further research testing this hierarchical structure in younger populations before generalizations can be made. Adolescence, in particular, is a significant risk period for the onset of psychopathology, warranting further attention (Costello, Copeland, & Angold, 2011). The current study tested competing structural models of psychopathology in a sample of adolescent twin pairs from the Wisconsin Twin Project, allowing for estimation of the heritability of the general P factor. Lastly, associations with parental psychopathology were considered. It was hypothesized that the bifactor model would exhibit the best fit to the data and that the general P factor would be highly heritable.
Five hundred five adolescent twin pairs (mean age 13.23 years) and their parents completed independent diagnostic interviews (DISC and CIDI, respectively), providing self-reports of symptomology across several DSM-IV disorders. Two-factor oblique, bifactor, and 1-factor models were tested utilizing adolescent symptom counts. The bifactor model exhibited the best fit to the data (χ2 (25) = 114.007, RMSEA = .059, CFI = .966, TL I= .938). An AE model was the best fit to the P factor, with 56% of the variance explained by additive genetic factors. Lastly, mixed model regression analyses were conducted to test for associations between parental diagnoses and adolescents’ general liability to psychopathology. Paternal depression and both paternal and maternal anxiety were significantly associated with adolescent P factor scores (β=.21 (.08), p< .05, β=.11 (.05), p< .05, and β=.17 (.07), p< .05, respectively). Conversely, parental alcohol dependence/abuse (a proxy for parental externalizing) was not associated with adolescent P factor scores.
These findings provide evidence of a moderately heritable general P factor underlying adolescent psychopathology. Additionally, significant associations with parental psychopathology provide external validation of the adolescent bifactor model. Future directions include modeling the hierarchical structure of parental psychopathology and testing whether the intergenerational transmission of psychopathology is sufficiently explained at the level of the P factor. Lastly, application of the nuclear twin-family design can elucidate whether conferral of genetic risk sufficiently explains the intergenerational transmission of this general liability to psychopathology or whether environmental transmission effects exert additional influence. These findings stand to make a significant contribution to science, as the traditional nosological approaches to classification of psychopathology, which have so long informed our research and treatment, are called into question.
Caspi, A., Houts, R. M., Belsky, D. W., Goldman-Mellor, S. J., Harrington, H., Israel, S., ... Moffitt, T. E. (2014). The p factor: One general psychopathology factor in the structure of psychiatric disorders? Clinical Psychological Science, 2(2), 119-137.
Costello, E. J., Copeland, W., & Angold, A. (2011). Trends in psychopathology across the adolescent years: What changes when children become adolescents, and when adolescents become adults? Journal of Child Psychology and Psychiatry, 52(10), 1015-1025.
Psychopathology (e.g., Internalizing, Externalizing, Psychosis) , Statistical Methods
