There is an urgent need to identify biomarkers for major depressive disorder.

Low serum BDNF has promise as a biomarker for major depressive disorder.

Low serum BDNF was associated with worse depressive symptoms at baseline.

Serum BDNF did not predict the new onset of major depressive disorder.

Vitamin D and omega-3 supplements did not alter serum BDNF levels over 2 years.

This study: 1) examined cross-sectional and longitudinal relations of serum brain-derived neurotrophic factor (BDNF) to late-life depression (LLD); 2) tested effects of vitamin D3 and omega-3s on change in BDNF; 3) explored modifying or mediating roles of BDNF on effects of vitamin D3 and omega-3s for LLD. We selected 400 adults from a completed trial of vitamin D3 and omega-3 supplements for LLD prevention. BDNF was measured using an enzyme-linked immunosorbent assay. We administered semi-structured diagnostic interviews and Patient Health Questionnaire [PHQ]-9 to ascertain outcomes at baseline (depression caseness vs. non-caseness; PHQ-9) and at 2-year follow-up among baseline non-depressed individuals (incident vs. no incident MDD; change in PHQ-9). At baseline, while there were no significant differences in mean serum BDNF comparing depression cases and non-cases, being in the lowest vs. highest serum BDNF quartile was significantly associated with worse depressive symptoms. There were no significant longitudinal associations between serum BDNF and LLD. Neither supplement significantly affected change in BDNF; serum BDNF did not appear to modify or mediate treatment effects on LLD. In conclusion, we observed significant cross-sectional but not longitudinal associations between serum BDNF levels and LLD. Vitamin D3 or omega-3s did not alter serum BDNF over 2 years.

BDNF

Depression

Vitamin D3

Omega-3s

Geriatric

Brain-derived neurotrophic factor

Major depressive disorder

Patient Health Questionnaire-9

Patient Health Questionnaire-8

VITamin D and OmegA-3 TriaL

VITamin D and OmegA-3 TriaL-Depression Endpoint Prevention

Clinical and Translational Science Center

Mini-International Neuropsychiatric Interview

Diagnostic and Statistical Manual of Mental Disorders

Selective serotonin reuptake inhibitor

© 2023 Published by Elsevier Ltd.