Reverse MR analyses were performed, and the results indicated that depression had no causal effect on acetoacetate (OR = 1.178, 95% CI = 0.534–2.599, P = 0.685), apolipoprotein A-I (OR = 0.800, 95% CI = 0.358–1.782, P = 0.585), glucose (OR = 1.028, 95% CI = 0.497–2.127, P = 0.940), glutamine (OR = 0.569, 95% CI = 0.276–1.170, P = 0.125), glycoproteins (OR = 1.982, 95% CI = 0.873–4.501, P = 0.102), isoleucine (OR = 1.614, 95% CI = 0.791–3.293, P = 0.188), and urea (OR = 1.349, 95% CI = 0.545–3.338, P = 0.518). This evidence concerns the gene APOA1 and major depressive disorder.