Common Factors and Interpretation of the p Factor of Psychopathology

Distal-to-proximal etiologically relevant variables associated with the general (p) and specific factors of psychopathology

BACKGROUND

The general factor of psychopathology, often denoted as p, captures the common variance among a broad range of psychiatric symptoms. Specific factors are co-modeled based on subsets of closely related symptoms. This paper investigated the extent to which wide-ranging genetic, personal, and environmental etiologically relevant variables are associated with p and specific psychopathology factors.

METHODS

Using data from four waves (ages 11-19) of TRAILS, we modeled a bifactor model of p and four specific factors [internalizing, externalizing, ADHD, Autism Spectrum Disorder (ASD)]. Next, we examined the associations of 19 etiologically relevant variables with these psychology factors using path models that organized the variables according to the distal-to-proximal risk principle.

RESULTS

Collectively, the etiologically relevant factors, including temperament traits, accounted for 55% of p's variance, 46% in ADHD, 35% in externalizing, 19% in internalizing, and 7% in ASD. The low 7% is due to insufficient unique variance in ASD indicators that load more strongly on p. Excluding temperament, variables accounted for 29% variance in p, 9% ADHD, 14% EXT, 7% INT, and 4% ASD. Most etiologically relevant factors were generic, predicting p. In addition, we identified effects on specific factors in addition to effects on p (e.g., parental SES, executive functioning); only effects on specific factors (e.g., parental rejection); opposite effects on different factors [e.g., diurnal cortisol (high INT but low EXT, p); developmental delay (high ASD and p but low EXT)]. Frustration, family functioning, parental psychopathology, executive functioning, and fearfulness had strong effects on p.

CONCLUSIONS

(1) Strong generic effects on p suggest that etiologically relevant factors and psychopathology tend to cluster in persons. (2) While many factors predict p, additional as well as opposite effects on specific factors indicate the relevance of specific psychopathology factors in understanding mental disorder. (3) High frustration, neurodevelopmental problems, and a disadvantaged family environment primarily characterize p.

The general psychopathology factor (p) from adolescence to adulthood: Exploring the developmental trajectories of p using a multi-method approach

Considerable attention has been directed towards studying co-occurring psychopathology through the lens of a general factor (p-factor). However, the developmental trajectory and stability of the p-factor have yet to be fully understood. The present study examined the explanatory power of dynamic mutualism theory - an alternative framework that suggests the p-factor is a product of lower-level symptom interactions that strengthen throughout development. Data were drawn from a population-based sample of girls (N = 2450) who reported on the severity of internalizing and externalizing problems each year from age 14 to age 21. Predictions of dynamic mutualism were tested using three distinct complementary statistical approaches including: longitudinal bifactor models, random-intercept cross-lagged panel models (RI-CLPMs), and network models. Across methods, study results document preliminary support for mutualistic processes in the development of co-occurring psychopathology (that is captured in p). Findings emphasize the importance of exploring alternative frameworks and methods for better understanding the p-factor and its development.

On the Meaning of the "P Factor" in Symmetrical Bifactor Models of Psychopathology: Recommendations for Future Research From the Bifactor-(S-1) Perspective

Symmetrical bifactor models are frequently applied to diverse symptoms of psychopathology to identify a general P factor. This factor is assumed to mark shared liability across all psychopathology dimensions and mental disorders. Despite their popularity, however, symmetrical bifactor models of P often yield anomalous results, including but not limited to nonsignificant or negative specific factor variances and nonsignificant or negative factor loadings. To date, these anomalies have often been treated as nuisances to be explained away. In this article, we demonstrate why these anomalies alter the substantive meaning of P such that it (a) does not reflect general liability to psychopathology and (b) differs in meaning across studies. We then describe an alternative modeling framework, the bifactor-(S-1) approach. This method avoids anomalous results, provides a framework for explaining unexpected findings in published symmetrical bifactor studies, and yields a well-defined general factor that can be compared across studies when researchers hypothesize what construct they consider "transdiagnostically meaningful" and measure it directly. We present an empirical example to illustrate these points and provide concrete recommendations to help researchers decide for or against specific variants of bifactor structure.

Utility and validity of the Brief Psychiatric Rating Scale (BPRS) as a transdiagnostic scale

The Brief Psychiatric Rating Scale (BPRS) was originally conceived to assess psychopathology in several psychiatric disorders, making it an appropriate candidate to be used as a transdiagnostic instrument. We analyzed the utility and validity of the BPRS in a diagnostically heterogeneous sample of 600 psychiatric inpatients. As a comparator, we chose the mini-ICF-APP, a scale used to measure functioning and impairment across the diagnostic spectrum. Both scales had good internal consistency. The BPRS and the mini-ICF-APP showed a moderate correlation, with good levels of agreement. We were able to identify general symptoms present across the diagnostic spectrum, influencing severity and a cluster of symptoms specific for each diagnosis. Our results show the utility and validity of the BPRS as a transdiagnostic assessment tool that could easily be introduced in routine clinical work.

Folk Classification and Factor Rotations: Whales, Sharks, and the Problems With the Hierarchical Taxonomy of Psychopathology (HiTOP)

The Hierarchical Taxonomy of Psychopathology (HiTOP) uses factor analysis to group people with similar self-reported symptoms (i.e., like-goes-with-like). It is hailed as a significant improvement over other diagnostic taxonomies. However, the purported advantages and fundamental assumptions of HiTOP have received little, if any scientific scrutiny. We critically evaluated five fundamental claims about HiTOP. We conclude that HiTOP does not demonstrate a high degree of verisimilitude and has the potential to hinder progress on understanding the etiology of psychopathology. It does not lend itself to theory-building or taxonomic evolution, and it cannot account for multifinality, equifinality, or developmental and etiological processes. In its current form, HiTOP is not ready to use in clinical settings and may result in algorithmic bias against underrepresented groups. We recommend a bifurcation strategy moving forward in which the DSM is used in clinical settings while researchers focus on developing a falsifiable theory-based classification system.

Drs. Constantinou and Fonagy Reply

We thank Aristodemou and Fried¹ for their thoughtful comments on our article about changes in the psychopathology bifactor dimensions over a psychosocial intervention.² Aristodemou and Fried expressed concerns over our interpretation of the p factor and our selection of the bifactor model over alternative models. We will address each concern and highlight the issues they raise for the field more broadly.