title: Serum BDNF concentrations show strong seasonal variation and correlations with the amount of ambient sunlight.
abstract: Earlier findings show seasonality in processes and behaviors such as brain plasticity and depression that in part are regulated by Brain-Derived Neurotrophic Factor (BDNF). Based on this we investigated seasonal variation in serum BDNF concentrations in 2,851 persons who took part in the Netherlands Study of Depression and Anxiety (NESDA). Analyses by month of sampling (monthly n's >196) showed pronounced seasonal variation in serum BDNF concentrations (P<.0001) with increasing concentrations in the spring-summer period (standardized regression weight (ß) = 0.19, P<.0001) and decreasing concentrations in the autumn-winter period (ß = -0.17, P<.0001). Effect sizes [Cohen's d] ranged from 0.27 to 0.66 for monthly significant differences. We found similar seasonal variation for both sexes and for persons with a DSM-IV depression diagnosis and healthy control subjects. In explorative analyses we found that the number of sunshine hours (a major trigger to entrain seasonality) in the week of blood withdrawal and the 10 weeks prior to this event positively correlated with serum BDNF concentrations (Pearson's correlation coefficients ranged: 0.05-0.18) and this could partly explain the observed monthly variation. These results provide strong evidence that serum BDNF concentrations systematically vary over the year. This finding is important for our understanding of those factors that regulate BDNF expression and may provide novel avenues to understand seasonal dependent changes in behavior and illness such as depression. Finally, the findings reported here should be taken into account when designing and interpreting studies on BDNF.
authors.affiliation: Institute of Psychology, Leiden University, Leiden, The Netherlands. molendijkml@fsw.leidenuniv.nl
authors.forename: Marc L
authors.initials: ML
authors.lastname: Molendijk
authors.forename: Judith P M
authors.initials: JP
authors.lastname: Haffmans
authors.forename: Boudewijn A A
authors.initials: BA
authors.lastname: Bus
authors.forename: Philip
authors.initials: P
authors.lastname: Spinhoven
authors.forename: Brenda W J H
authors.initials: BW
authors.lastname: Penninx
authors.forename: Jos
authors.initials: J
authors.lastname: Prickaerts
authors.forename: Richard C
authors.initials: RC
authors.lastname: Oude Voshaar
authors.forename: Bernet M
authors.initials: BM
authors.lastname: Elzinga
mesh_terms: D000328:Adult; D001007:Anxiety / Q000097:blood*; D015992:Body Mass Index; D019208:Brain-Derived Neurotrophic Factor / Q000097:blood*; D016022:Case-Control Studies; D003863:Depression / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D012044:Regression Analysis; D012621:Seasons; D013472:Sunlight; D013997:Time Factors
chemical_list: D019208:Brain-Derived Neurotrophic Factor