by Alexander Williams, MS
Northwestern University
Cross-sectional inquiries make clear that personality and psychopathology are reliably linked (Kotov et al., 2010). For decades, theorists have proposed and studied a set of models that purport to account for the overlap between personality and psychopathology. Research in this area has the potential to guide prevention efforts (via targeting of personality traits) and enhance our understanding of the etiology of mental health problems. What are the important models and how do they differ? In this primer, I will review the most influential models.
Common Cause
The common cause model states that associations between personality and psychopathology arise due to shared etiological factors. Findings from behavior genetics research lend credence to this model. For instance, Kendler et al. (2006) found a substantial genetic correlation between neuroticism and depression, meaning that the genes that confer risk for high neuroticism overlap with those that confer risk for depression. Analogous genetic correlations have been detected between psychopathic traits and dimensions representing internalizing and externalizing problems (Blonigen et al., 2005). The common cause model can be considered a weak version of the continuum model, reviewed next.
Continuum/Spectrum
This model underlines the overlap between personality features and the symptoms of psychological disorders. The extent of this overlap, according to this model, provides basis for continuity. Continuity is the notion that there is no clear dividing line between personality and psychopathology. Evidence that measures of traits and disorders are strongly associated (e.g., Kotov et al., 2010) support this model. However, as Durbin and Hicks (2014) note, the model is difficult to falsify without applying a threshold to such associations. One prediction of the continuum model is that change in symptomatology should also result in change in personality if the two truly reflect the same dimension.
Predisposition/Scar
The predisposition and scar models both posit causal effects between personality and psychopathology but in opposite directions. Scarring reflects the idea that personality can be permanently affected by the experience of clinically significant psychopathology after it remits. There is scant evidence to support this idea, at least in the context of depression (Klein et al., 2011). Neither the common cause nor the continuum model consider the possibility of effects between personality and psychopathology. Predisposition and scar models are often explored in concert where vulnerability and scar effects can be compared (e.g., Jylhä et al., 2009). In strong versions of these causal models, distinct etiologies of personality and psychopathology are assumed.
Each of the above models orients longitudinal research on the relationships between personality and psychopathology. Future tests of the above models will be most useful when they permit falsification of the theory tested (e.g., Lakens, 2018). In other words, tests of these models designed to rule out effects of a certain size or larger will help narrow down the set of possible models and facilitate the progression of this research area. For a more detailed discussion of these models and their relative evidence, see Hicks and Durbin (2014).
Implications for Research, Clinical Practice, and Education
All these models share the implication that the research strategy of assessing personality as only a predisposition that predicts later clinical problems is lacking. Thus, a longitudinal strategy where personality is assessed at baseline but only psychopathology is assessed at later assessments poses serious limitations and constrains the analyst to the unconfirmed idea of predisposition being the defining way that personality relates to psychopathology. As for clinical practice, both the common cause and continuum models suggest that personality assessment and targeting is relevant for clinicians. If personality is continuous (or at least shares significant overlap) with psychopathology, then the assessment and targeting of personality in treatment is a valid goal. Indeed, a newer transdiagnostic treatment informed by these perspectives, the Unified Protocol (Farchione et al., 2012), explicitly targets neuroticism.
The objective in such newer interventions may be more along the lines of reducing a characteristic tendency (e.g., avoiding aversive emotions) that sets the stage for more profound clinical problems versus achieving remission of a specific mental disorder. This change in approach is advantageous from the training standpoint because learning one general protocol is more expedient than learning a number of separate protocols matched to specific clinical problems. Finally, these models also have an important implication for education about psychopathology. Based on these models, covering personality and psychopathology in separate courses (or in separate textbooks) is not consistent with their interrelations. To understand the development of psychopathology, some understanding of personality and its overlap with clinical problems is needed and should be explicitly incorporated into course material.
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References
Blonigen, D. M., Hicks, B. M., Krueger, R. F., Patrick, C. J., & Iacono, W. G. (2005). Psychopathic personality traits: Heritability and genetic overlap with internalizing and externalizing psychopathology. Psychological Medicine, 35(5), 637-648. https://doi.org/10.1017/S0033291704004180
Durbin, C. E., & Hicks, B. M. (2014). Personality and psychopathology: A stagnant field in need of development. European Journal of Personality, 28(4), 362–386. https://doi.org/10.1002/per.1962
Farchione, T. J., Fairholme, C. P., Ellard, K. K., Boisseau, C. L., Thompson-Hollands, J., Carl, J. R., Gallagher, M. W., & Barlow, D. H. (2012). Unified protocol for transdiagnostic treatment of emotional disorders: A randomized controlled trial. Behavior Therapy, 43(3), 666-678. https://doi.org/10.1016/j.beth.2012.01.001
Jylhä, P., Melartin, T., Rytsälä, H., & Isometsä, E. (2009). Neuroticism, introversion, and major depressive disorder—traits, states, or scars? Depression and Anxiety, 26(4), 325–334.
https://doi.org/10.1002/da.20385
Kendler, K. S., Gatz, M., Gardner, C. O., & Pederse, N. L. (2006). Personality and Major Depression. Archives of General Psychiatry, 63(10), 1113–1120. https://doi.org/10.1001/archpsyc.63.10.1113
Klein, D. N., Kotov, R., & Bufferd, S. J. (2011). Personality and depression: Explanatory models and review of the evidence. Annual Review of Clinical Psychology, 7, 269–295.
https://doi.org/10.1146/annurev-clinpsy-032210-104540
Kotov, R., Gamez, W., Schmidt, F., & Watson, D. (2010). Linking “big” personality traits to anxiety, depressive, and substance use disorders: A meta-analysis. Psychological Bulletin, 136(5), 768–821.
https://doi.org/10.1037/a0020327
Lakens, D., Scheel, A. M., & Isager, P. M. (2018). Equivalence testing for psychological research: A tutorial. Advances in Methods and Practices in Psychological Science, 1(2), 259–269.
https://doi.org/10.1177/2515245918770963
Ormel, J., Jeronimus, B. F., Kotov, R., Riese, H., Bos, E. H., Hankin, B., Rosmalen, J. G.M., & Oldehinkel, A. J. (2013). Neuroticism and common mental disorders: Meaning and utility of a complex relationship. Clinical Psychology Review, 33(5), 686–69
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