Plasma brain-derived neurotrophic factor in bipolar and unipolar depression

BDNF nelle depressioni bipolare ed unipolare

L. Dell'Osso*, C. Bianchi*, A. Del Debbio*, I. Roncaglia*, A. Veltri*, M. Carlini*, M. Catena Dell'Osso*, N. Origlia**, L. Domenici** ***, D. Marazziti*, A. Piccini* *

Dipartimento di Psichiatria, Neurobiologia, Farmacologia e Biotecnologie, University of Pisa; ** Institute of Neuroscience, National Research Council, Pisa; *** Dipartimento di Scienze e Tecnologie Biomediche, University of L'Aquila



There is increasing evidence that Brain- Derived Neurotrophic Factor may be involved in the pathophysiology of depression and the actions of antidepressants. At the same time, the differential diagnosis between unipolar and bipolar depression is often a challenge with important treatment implications. The aim of the present study was to analyze the relationship between Brain- Derived Neurotrophic Factor levels and clinical variables in subjects with unipolar versus bipolar depression.


Thirty-three outpatients (17 with unipolar and 16 with bipolar depression) and 15 healthy controls were consecutively enrolled at the Department of Psychiatry, Neurobiology, Pharmacology and Biotechnologies of the University of Pisa. Brain-Derived Neurotrophic Factor concentrations were measured with an enzyme-linked immunosorbent assay method. Severity of depression was assessed by means of the 21-item Hamilton Rating Scale for Depression and the Clinical Global Impressions – Severity of Illness scale. Fifteen healthy subjects, with no history of past or current chronic physical or mental disorders and not taking regular medications, were recruited as the control group.


Compared to healthy controls, plasma Brain-Derived Neurotrophic Factor concentrations were significantly reduced in patients with unipolar or bipolar depression, with no significant difference between the two groups. Statistical analyses showed significant intergroup differences in the age of onset, presence of psychotic symptoms and cognitive disturbances (Table I). Significant and negative correlations were found in the total sample between Brain-Derived Neurotrophic Factor levels and the Hamilton Rating Scale for Depression total scores (r = – 0.511, p = 0.002), the retardation factor scores (r = -0.416, p = 0.016) and Clinical Global Impressions “severity of illness” scores (r = -0.385, p = 0.027). When the same analyses were repeated in each group separately, these findings were confirmed only in patients with bipolar depression (Figs. 1, 2).


Our results show that lower Brain-Derived Neurotrophic Factor levels may be related to both severity of depression and retardation symptoms in bipolar depression. Further studies need to ascertain whether and how the Brain-Derived Neurotrophic Factor levels may be associated with any psychopathological dimensions of the depressive state and be used as a biological marker to differentiate bipolar from unipolar depression.

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