LEP and major depressive disorder: Consistent with Dehzad et al. 2023 [28], Atkin et al. 2017 [132] also observed a significant decrease in plasma leptin levels following a curcuminoid intake of 250–1000 mg/day for 4–24 weeks [standardized mean difference (SMD) = 0.69; 95% CI −1.16 to −0.23; p = 0.003; I2 = 76.53%)] in subjects with T2DM, metabolic syndrome, and major depressive disorder.