Stability of personality traits in bipolar disorder: Findings from a longitudinal cohort

•For some individuals with bipolar disorder, personality traits are about as stable as in healthy controls, but for a proportion of our bipolar sample, personality traits change in a clinically significant way.•There are mood-state effects of depression on self-reported personality traits within bipolar disorder.•Changes in personality scores over time are not related changes in mood with the exception of changes in Neuroticism are related to change in depression within our bipolar sample. Individuals with bipolar disorder (BD) show different personality profiles compared to non-psychiatric populations, but little is known about the temporal stability of personality traits over time, and if changes in mood state drive changes in personality. Participants were 533 BD and 185 healthy controls (HC) who completed the NEO-Personality Inventory-Revised (NEO-PI-R) and clinician-administered measures of mood at baseline. One-hundred-eighty BD and 79 HC completed the measures at 5-year follow-up and 60 BD and 16 HC completed the measures at 10-year follow-up. The above measures and demographic information, but not other clinical status indicators the BD illness, were used in analyses. The BD group has higher Neuroticism (N)/N facets and lower Extraversion (E)/E facets and Consciousness (C)/C facets compared to HC. Significant mean-level changes existed within groups but were small in magnitude, and groups showed similar moderate-to-high rank-order stability. Change in (N)/N facets shows an association with change in depression, but changes in all other NEO-PI-R scores are not associated with changes in mood. Personality traits are clinically stable in part of our bipolar sample using clinically relevant interpretation of changes in T scores; however, some BD subjects did show more reliable changes in personality traits than the healthy controls. Reliance on self-report measurement and not all our participants completed the 5- and 10-year follow-up personality assessment who were eligible to do so. Mean-level and rank-order personality scores show only modest changes, so most personality changes over time are not systematic. Observed changes in personality traits are not explained by changes in mood with the exception of Neuroticism, suggesting other factors influence changes in personality.