Brain-derived neurotrophic factor (BDNF) plays a role in neuroplasticity, appetite regulation, and reward processing. Its possible involvement in eating disorders (EDs) has been investigated; however, Show more
Brain-derived neurotrophic factor (BDNF) plays a role in neuroplasticity, appetite regulation, and reward processing. Its possible involvement in eating disorders (EDs) has been investigated; however, contradictory findings and substantial methodological heterogeneity have prevented definitive conclusions. To systematically evaluate peripheral BDNF levels in individuals with EDs, healthy controls and recovered individuals. A systematic review with meta-analysis was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement (CRD420250654199). Observational studies and randomized controlled trials comparing BDNF levels in individuals with and without EDs were included. The Newcastle-Ottawa Scale and risk-of-bias tool for randomized trials were used. Twenty-one studies were included. BDNF serum levels were significantly lower in acute anorexia (AN) compared with healthy controls (Standardized Mean Difference [SMD] = -0.49;p < 0.001,n = 17), with significance maintained after excluding outliers (SMD = -0.41; p < 0.001,n = 8). No significant difference was found between recovered AN and controls. Bulimia nervosa (BN) individuals showed significantly lower BDNF serum levels (SMD = -0.72;p < 0.001,n = 4). Longitudinal studies showed a significant increase in serum BDNF levels after recovery (SMD = 1.78;p = 0.003,n = 6). These findings support a predominantly state-related association between peripheral BDNF levels and illness stage in AN and BN, rather than a stable condition-specific. Evidence for binge-eating disorders is extremely limited, relying on a single eligible study. Interpretation is constrained by methodological heterogeneity, variability in recovery definitions, and the largely correlational nature of the evidence. Further standardized, high-quality longitudinal studies are needed to clarify whether peripheral BDNF alterations reflect state-related mechanisms, trait vulnerability, or dynamic biological changes across illness stages. Show less