BDNF and major depressive disorder: The reason for BDNF reductions in this sample receiving TAU over a 3 month period is unclear; for example, even over several years a lack of significant change in serum BDNF has been reported.28,29 Conversely, a report of reduced BDNF manifesting over a long period in people who had a depressive illness compared with those without concluded that the BDNF can be considered a state marker of affective illness.30 However, our population were not experiencing depressive symptoms during the trial and subsyndromal depression severity did not differ between groups or timepoints.5