Abstract
Depression has been associated with inflammation, and inflammation may both influence and interact with growth factors such as brain-derived neurotrophic factor (BDNF). Both the functional Val66Met BDNF polymorphism (rs6265) and BDNF levels have been associated with depression. It is thus plausible that decreased BDNF could mediate and/or moderate cytokine-induced depression. We therefore prospectively employed the Beck Depression Inventory-II (BDI-II), the Hospital Anxiety and Depression Scale (HADS), and the Montgomery-Asberg Depression Rating Scale (MADRS) in 124 initially euthymic patients during treatment with interferon-alpha (IFN-alpha), assessing serum BDNF and rs6265. Using mixed-effect repeated measures, lower pretreatment BDNF was associated with higher depression symptoms during IFN-alpha treatment (F-144,F-17.2 = 6.8; P<0.0001). However, although the Met allele was associated with lower BDNF levels (F-1,F-83.0 = 5.0; P = 0.03), it was only associated with increased MADRS scores (F-4,F-8.9 = 20.3; P<0.001), and not the BDI-II or HADS. An exploratory comparison of individual BDI-II items indicated that the Met allele was associated with suicidal ideation, sadness, and worthlessness, but not neurovegetative symptoms. Conversely, the serotonin transporter promoter polymorphism (5-HTTLPR) short allele was associated with neurovegetative symptoms such as insomnia, poor appetite and fatigue, but not sadness, worthlessness, or suicidal ideation. IFN-alpha therapy further lowered BDNF serum levels (F-4,F-37.7 = 5.0; P = 0.003), but this decrease occurred regardless of depression development. The findings thus do not support the hypothesis that decreasing BDNF is the primary pathway by which IFN-alpha worsens depression. Nonetheless, the results support the hypothesis that BDNF levels influence resiliency against developing inflammatory cytokine-associated depression, and specifically to a subset of symptoms distinct from those influenced by 5-HTTLPR. Neuropsychopharmacology (2013) 38, 985-995; doi:10.1038/npp.2012.263; published online 16 January 2013