D Ceylan^a, A Özerdem^{a, b}, ŞN Gürz Yalçın^c, C Hidiroğlu^b, Y Ç Arslan^a, B Bağcı^a, M Bayind, Ö Aydemir^e, C Cengisiz^e, H Resmi^f, Z Tunca^a

^aDepartment of Psychiatry, Dokuz Eylul University Medical School, Izmir, Turkey, ^bDepartment of Neuroscience, Dokuz Eylul University Health Sciences Institute, Izmir, Turkey, ^cDepartment of Psychiatry, Etlik Zubeyde Hanim Women’s Health Teaching and Research Hospital, Ankara, Turkey, ^dDepartment of Psychiatry, Nevsehir Dr I Sevki Atasagun Public Hospital, Nevsehir, Turkey, ^eDepartment of Psychiatry, Celal Bayar University Medical School, Manisa, Turkey, ^fDepartment of Biochemistry, Dokuz Eylul University Medical School, Izmir, Turkey

Introduction: Despite discrepancies in serum BDNF (brain-derived neurotrphic factor) levels in different states of bipolar disorder (BD), low peripheral BDNF levels are generally accepted as a biomarker for illness activity and progression. This is the first study investigating serum BDNF levels as a candidate endophenotype for BD.

Objective: We aimed to compare serum BDNF levels in bipolar patients, their unaffected first degree relatives and in healthy controls.

Method: Patients with DSM-IV BD (n = 53) either in euthymic (n = 30), depressed or manic (n = 23) states, their first degree relatives (n = 19) and 37 healthy controls were included in the study. Diagnosis was confirmed using Structural Clinical Interview for DSM-IV-TR (SCID-I); Symptomatic and syndromal severity were assessed using Young Mania Rating Scale (YMRS), Hamilton Depression Scale-17 (HAM-D 17), Clinical Global Impression Scale (CGI). Serum BDNF levels were measured with an enzyme-linked immunosorbent assay (ELISA) method.

Results: The mean serum BDNF levels of in-episode bipolar patients (4.27 ± 1.09 ng/ mL) were significantly lower than that of euthymic patients (8.04 ± 2.20) (p < 0.00), first degree relatives (7.14 ± 2.13 ng/mL) (p < 0.000), and healthy controls (7.05 ± 2.64 ng/mL) (p < 0.000). There was no significant difference between the latter three groups. Serum BDNF levels correlated negatively with HAM-D, YMRS and CGI scores.

Conclusion: Our findings confirm the existing data that serum BDNF levels are abnormally low in active phases of BD and related with episode severity. We suggest that low serum BDNF levels are nonspecific state markers and cannot be identified as an endophenotype for BD.

Keywords: brain-derived neurothrophic factor, bipolar disorder, endophenotype, biomarker

Bipolar Disorders ª 2011 John Wiley & Sons A/S, Bipolar Disorders, 14 (Suppl. 1) 52–138