BDNF in late-life depression: effect of SSRI usage and interaction with childhood abuse.

Brain-Derived Neurotrophic Factor (BDNF) serum levels are abnormally low in depressed patients as compared to healthy controls and normalize with SSRI treatment. The aim of this study is to examine serum BDNF levels in late-life depression, stratified for SSRI usage, and to explore the relation between BDNF levels and specific depression characteristics as well as between BDNF levels and early and recent life stressors in late-life depression. We assessed serum BDNF levels in 259 depressed patients not using an SSRI, 99 depressed patients using an SSRI and 119 non-depressed controls (age range 60-93 years). Depressive disorders were diagnosed with the Composite International Diagnostic Interview (CIDI, version 2.1). Serum BDNF levels were significantly higher in depressed patients who used an SSRI compared to depressed patients not using SSRIs and compared to non-depressed controls, when adjusted for age, sex, life style characteristics, cognitive functioning and somatic comorbidity. Recent life-events, assessed with the List of Threatening Events-Questionnaire, were significantly associated with lower BDNF levels in non-depressed subjects only. Although a summary score of early traumatization (before the age of 16 years) was not associated with serum BDNF levels in any of the three groups, we found an interaction between a history of severe physical abuse and SSRI usage in the depressed group. Interestingly, higher serum levels of BDNF in depressed patients using SSRIs were only found in those patients without a history of severe childhood abuse and not in those with a history of severe childhood abuse.