The pathoplasticity model can be evaluated in longitudinal studies of persons with depressive disorders by examining the associations among personality traits and clinical features, course, and treatment response. Specifically, the pathoplasticity model posits that the trait would predict these outcomes even after controlling for initial illness severity and other prognostic factors. Of note, an alternative explanation of such results is that the personality trait is a marker for a more severe, chronic, or etiologically distinct subgroup, rather than having a causal influence on the expression of the disorder. A multiwave follow-up of individuals with a depressive disorder could be helpful in ruling out this possibility. If the trait influences the disorder course directly, rather than because it is an indicator of a latent disorder class, changes in personality scores should predict subsequent changes in outcomes.
