Neuroplastic processes are thought to be involved in the pathophysiology of many psychiatric disorders, including major depression. It has been hypothesized that the brain-derived neurotrophic factor (BNDF), a key factor in neuroplasticity, is associated with depressive disorders. Our study evaluated the pre- and post-treatment levels of BDNF in a group of depressed patients and compared them with healthy controls. In order to exclude the effects of gender on neuroplasticity, our study group was restricted to women exclusively and consisted of 20 depressive patients and 20 healthy controls, with similar age and educational level distribution. Blood samples were collected before the treatment and on the sixth week of the treatment with 10 mg S-citalopram. The pre-treatment BDNF levels of the depressed patients were found to be lower than those of the healthy subjects. During the sixth week, the BDNF levels of depressive patients were significantly higher than the pre-treatment levels but similar to those of control subjects. These findings suggest that BDNF level may be an important factor in the etiopathogenesis of depression and may have a role in the action mechanism of antidepressant drugs.