Associations between Brain-Derived Neurotrophic Factor Plasma Levels and Severity of the Illness, Recurrence and Symptoms in Depressed Patients

Background: There is increasing evidence that the brain-derived neurotrophic factor (BDNF) is involved in the pathophysiology of mood disorders and that its peripheral levels represent a reliable mirror of its concentration in the brain. The aim of the present study was to measure BDNF plasma levels in patients affected by major depression and to explore the possible relationship between the biological parameter and characteristics of the illness. Method: BDNF plasma levels were evaluated in 30 inpatients suffering from major depression, according to DSM-IV criteria, by means of a commonly employed ELISA method. The clinical characteristics were assessed by the Hamilton Rating Scale for Depression (HRSD) and the Clinical Global Impression Scale. Results: BDNF plasma levels were significantly lower in the patients with the severest illness compared with the others, and the same was true for patients with dissociative symptoms, severe sleep disturbance and recurrent depression. A significant and negative correlation was observed between the biological parameter and the retardation factor score of the HRSD. Conclusion: These findings suggest that low BDNF levels are related to both recurrence and severity of depression, as well as to symptoms typical of dysfunctions of the hypothalamic-pituitary-adrenal axis.