The relationship between antioxidant vitamins and mental disorders: a meta-analysis

Background: mental disorders are associated with oxidative stress. Antioxidant vitamins A, C and E exhibit antioxidant properties. Nevertheless, the association between antioxidant vitamins and mental disorders remains ambiguous. Methods: this meta-analysis compared the levels of dietary and blood vitamins A, C, and E between patients with attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), depression, and schizophrenia (SZ) and healthy controls. Furthermore, a Mendelian randomization (MR) post-meta-analysis approach was employed to explore the causal relationships between these antioxidant vitamins and mental health conditions. Results: dietary analysis indicated that patients with depression exhibited a significantly lower intake of vitamin A (SMD: -0.13; 95% CI: -0.21, -0.05; and P < 0.01), vitamin C (SMD: -0.18; 95% CI: -0.24, -0.13; and P < 0.01), vitamin E (SMD: -0.16; 95% CI: -0.28, -0.04; and P = 0.01), and carotenoids (SMD: -0.17; 95% CI: -0.20, -0.14; and P < 0.01) compared with controls. Blood analysis revealed that patients with depression had decreased blood levels of vitamin A (SMD = -0.18; 95% CI: -0.29, -0.06; and P < 0.01), vitamin C (SMD = -0.52; 95% CI: -0.94, -0.10; and P = 0.01), and vitamin E (SMD = -0.77; 95% CI: -1.39, -0.16; and P = 0.01). Similarly, patients with SZ demonstrated a reduced blood level of vitamin C (SMD = -0.85; 95% CI: -1.49, -0.21; and P = 0.01) and vitamin E (SMD = -0.92; 95% CI: -1.21, -0.62; and P < 0.01). However, no significant differences were found in the dietary or blood antioxidant vitamins in patients with ADHD and ASD. MR post-meta-analysis identified a causal relationship between SZ and vitamin C. Conclusions: patients with depression had lower levels of dietary and blood vitamins A, C, and E. Similarly, patients with SZ had reduced blood levels of vitamins C and E.