The proportionality hypothesis: Personality disorder traits weaken the link between impairment and change motivation

Clinical theory has long characterized personality disorders (PDs) as difficult to treat, reflecting limited insight into impairment, and harmonious with the self-concept. However, recent evidence suggests that PD traits can diminish over time and that individuals higher in PD traits report greater impairment and motivation to change. We proposed the proportionality hypothesis to reconcile these seemingly contradictory perspectives on PDs. This hypothesis suggests that people elevated in PD traits do acknowledge impairment and express motivation to change, but their motivation is reduced relative to the extent of their acknowledged impairment. In Study 1, participants reported their PD traits, current life impairment, and change motivation. As expected, PD traits were associated with greater impairment and change motivation. However, consistent with the proportionality hypothesis, the positive association between impairment and change motivation was weakened with increments in psychoticism and antagonism, and this attenuation was also apparent for the global PD-trait composite. Study 2 included Study 1's domain-general indicators of impairment and change motivation along with trait-specific indicators of these two constructs. Largely consistent with Study 1, the positive association between domain-general impairment and change motivation was weakened with increments in all PD traits except detachment as well as the global composite; however, proportionality effects failed to clearly extend to the trait-specific measures. We speculate about potential mechanisms underlying these patterns and highlight potential clinical implications and directions for future research. (PsycInfo Database Record (c) 2026 APA, all rights reserved).