Duration of last depressive episode may influence serum BDNF levels in remitted patients with major depression.

BACKGROUND

Brain-derived neurotrophic factor (BDNF) may have an important role in the pathophysiology of depression. Previous studies indicate that serum BDNF levels were lower in patients with depression and increased after treatment with antidepressants. However, results of studies on serum BDNF levels in remitted patients with depression have been inconsistent. The purpose of the present study was to determine which factors influence the alteration of serum BDNF levels in depression in the remitted state.

METHODS

Serum BDNF levels were evaluated in 75 remitted inpatients with major depressive disorder (MDD) and 108 controls. Multiple regression analyses were conducted using serum BDNF levels as the dependent variable; and the number of episodes, Hamilton Rating Scale for Depression score at admission, or duration of last depressive episode as independent variables.

RESULTS

Serum BDNF levels were lower in remitted patients with MDD than in controls (P < .001). Multiple regression analysis showed a significant effect between the duration of the last depressive episode and serum BDNF levels (P < .022).

CONCLUSIONS

Serum BDNF levels in remitted patients with MDD did not recover to the level of healthy controls, and lower serum BDNF levels were influenced by a longer duration of last depressive episode. It is possible that persistent hippocampal reduction in remitted depression may be caused by lower BDNF levels associated with a longer duration of the last depressive episode.