Does fluoxetine influence major depression by modifying five-factor personality traits?

Selective serotonin reuptake inhibitors (SSRIs) are effective in the treatment of depression, though response to them is difficult to predict. The aims of this study were two-fold: (1) to determine the differences in personality profile between patients with major depression and healthy control subjects and (2) to assess the effect of treatment with fluoxetine on personality domain scores and determine whether any of the personality traits can predict the outcome of antidepressant treatment.

The study included 53 patients with major depression and 53 healthy controls. The NEO-Five-Factor Inventory (NEO-FFI) was administered to all subjects before and after 24 weeks of treatment with fluoxetine.

The patients in an episode of major depression had a significantly different personality profile compared to healthy controls at baseline and the severity of their illness correlated with higher scores in the Neuroticism domain. Treatment with fluoxetine was associated with a reversal of high Neuroticism scores and low Extraversion scores in the whole sample and in a subgroup of responders but not in non-responders. Among the FFI personality domains, Agreeableness was a better predictor of treatment outcome than baseline HAMD-17 scores.

There was no placebo group, which would have permitted the evaluation of the effect of non-drug factors in treatment outcome and changes in personality domain scores. The sample size was only moderate.

The results suggest that (a) significant differences exist between the personality profiles of depressed patients and healthy control subjects and (b) responders to treatment with fluoxetine show significant changes in personality profile. These changes may be attributed to improvement of depressive symptoms.