The p Factor: One General Psychopathology Factor in the Structure of Psychiatric Disorders?

Abstract

Mental disorders traditionally have been viewed as distinct, episodic, and categorical conditions. This view has been challenged by evidence that many disorders are sequentially comorbid, recurrent/chronic, and exist on a continuum. Using the Dunedin Multidisciplinary Health and Development Study, we examined the structure of psychopathology, taking into account dimensionality, persistence, co-occurrence, and sequential comorbidity of mental disorders across 20 years, from adolescence to midlife. Psychiatric disorders were initially explained by three higher-order factors (Internalizing, Externalizing, and Thought Disorder) but explained even better with one General Psychopathology dimension. We have called this dimension the p factor because it conceptually parallels a familiar dimension in psychological science: the g factor of general intelligence. Higher p scores are associated with more life impairment, greater familiality, worse developmental histories, and more compromised early-life brain function. The p factor explains why it is challenging to find causes, consequences, biomarkers, and treatments with specificity to individual mental disorders. Transdiagnostic approaches may improve research.

Keywords: DSM; developmental psychopathology; psychiatric epidemiology.

Fig. 1

The structure of psychopathology Three models were tested using confirmatory factor analysis: a correlated-factors model (Model A), a hierarchical or bifactor model (Model B), and a 1-factor model (Model C) Model B′ shows the final revised hierarchical model Colored ovals represent latent (unobserved) continuous symptom trait factors colored boxes represent observed symptom counts for each disorder at each assessment age The following 11 disorder/symptoms were assessed alcohol dependence, cannabis dependence, dependence on hard drugs, tobacco dependence, conduct disorder, major depression, generalized anxiety disorder, fears/phobias, obsessive-compulsive disorder, mania and positive and negative schizophrenia symptoms. Disorder/symptoms were assessed at ages 18, 21, 26, 32, and 38 years (not all disorders were assessed at every age, but each disorder was measured at least three times; missing assessments are depicted by white space) Gray ovals represent method/state factors designed to pull out age- and assessment-related variance (e.g., interviewer effects, mood effects, and age-specific vulnerabilities) that was uncorrected with trait propensity toward psychopathology. Note Alc = alcohol; Can = cannabis; Drg = hard drugs Tob = tobacco; CD = conduct disorder; MDE = major depression; GAD = generalized anxiety disorder; Fears = fears/phobias; OCD = obsessive-compulsive disorder; Schiz = schizophrenia

Fig. 2

Association between p factor scores and age-3 brain Integrity. The p factor is standardized to a mean of 100 (SD = 15), and higher p scores Indicate more Generalized Psychopathology. The bars of the histograms graph the percentages of the sample at different levels of the p factor. The squares and standard error bars show the scores of individuals on the age-3 brain integrity factor as a function of p scores less than 85, 85 to 95, 95 to 105, 105 to 115, 115 to 125, and greater than 125. The regression line shows the correlation between the p factor and childhood brain integrity.

Fig. 3

The p factor. Many individuals manifest a brief episode of a gendered individual disorder, a smaller subset of individuals progress to develop persistent and increasingly impairing externalizing and internalizing disorders, whereas only a few individuals progress to extreme elevation of p, ultimately emerging with disordered thought processes.