Daily serum and salivary BDNF levels correlate with morning-evening personality type in women and are affected by light therapy

Introduction. BDNF is present in human serum and its level changes have been used as a marker of antidepressant efficacy in some psychiatric disorders. In addition, the positive effects of light therapy on major depression suggest that circadian-regulated factors should be taken into account in the management of mood disorders. The aim of the present study was to test ultradian fluctuations in serum and salivary BDNF levels and their interaction with light therapy in a sample of healthy women. Methods. The study included 16 young women. Psychopathological status and chronotype traits were assessed by SPAQ, BDI, STAI, TAS, and MEQ. Standard light treatment protocol was applied. Serum and saliva were collected at 8.00, 13.00 and 20.00 hrs on the same day and at the end of light therapy. Results. BDNF levels declined over the course of the day both in serum and saliva, and a correlation between diurnal BDNF trend and personality traits and habits characterizing the morning and evening types in healthy women was found. Conclusions. The present study is one of the first to show measurable BDNF in human saliva and to demonstrate its daily fluctuations in both saliva and serum of healthy young women. The correlation between diurnal changes in BDNF and the personality traits associated with body rhythms corroborates the notion that salivary BDNF may be a useful biomarker for stress-related research and different clinical investigations.