Neuroticism, introversion, and major depressive disorder--traits, states, or scars?

The extent to which measures of the personality dimensions of neuroticism and introversion are influenced by symptoms of depression and anxiety or by episodes of depression, and whether neuroticism alone or both traits predispose one to depression remain unclear.

Major depressive disorder patients (n=193) from the Vantaa Depression Study were interviewed at baseline and at 6 and 18 months, and a general population comparison group (n=388) was surveyed by mail. Patients' scores of neuroticism and extraversion-introversion were compared between time points, and before and after a possible recurrence of depression between interviews. Patients' scores at an index interview, when the level of depression was lowest, were compared with scores of the general population, after controlling for anxiety and depression.

Among depressive patients, neuroticism scores declined (from 17.2, SD 3.7-13.7, SD 5.6, P<0.001) and extraversion scores increased (from 10.0, SD 4.7-11.2, SD 4.5, P<0.001) with recovery during follow-up. The scores were not influenced by a recurrence of depression between measurements. In logistic regression, patients had higher neuroticism (odds ratio, OR 1.11, P=0.001) and lower extraversion (OR 0.92, P=0.003) than the general population.

The overall level of neuroticism is markedly and introversion somewhat higher in depressive patients than in the general population. Anxiety symptoms have some, and depressive symptoms a strong influence on neuroticism scores, but only depression has an impact on introversion during a depressive episode. In medium-term follow-up, depressive episodes are unlikely to result in a personality scar persisting after recovery from an episode.