Differences in Neuroticism and Extraversion Between Patients with Bipolar I or II and General Population Subjects or Major Depressive Disorder Patients

Background: Whether levels of neuroticism or extraversion differ between patients with bipolar disorder (BD), major depressive disorder (MDD) and subjects from the general population, or between BD I and BD II patients, remains unclear.

Methods: BD patients (n=191) from the Jorvi Bipolar Study, and MDD patients (n=358) from both the Vantaa Depression Study and the Vantaa Primary Care Depression Study cohorts, were interviewed at baseline and at 18 months. A general population comparison group (n=347) was surveyed by mail. BD patients' neuroticism and extraversion scores, measured by Eysenck Personality Inventory, were compared at an index interview, when the levels of depression and mania were lowest, with scores of MDD patients and general population controls. Comparisons were also made between BD I (n=99) and BD II (n=92) patients.

Results: In multinomial logistic regression, BD patients had higher neuroticism (OR=1.17, p<0.001) and lower extraversion (OR=0.92, p=0.003) than the general population. When entered simultaneously into the model, the effect of extraversion disappeared. In logistic regression, the levels of neuroticism and extraversion did not differ between BD and MDD patients, or between BD I and II patients.

Limitations: Patients' personality scores were not pre-morbid.

Conclusions: Levels of neuroticism and extraversion are unlikely to differ between BD and MDD patients, or between BD I and II patients. The overall level of neuroticism is moderately higher and extraversion somewhat lower in BD patients than in the general population. High neuroticism may be an indicator of vulnerability to both bipolar and unipolar mood disorders.