IGF1 and major depressive disorder: Only 5 articles reported comparisons of peripheral IGF-1 levels in patients with BD or MDD before and after treatment.16,18,19,21,24 In the meta-analysis of these studies, we did not find any significant difference between the peripheral IGF-1 levels in patients with BD or MDD before and after treatment (ESs = 0.23, 95% CI: −0.04 to 0.51, P = 0.092) (Figure 2B).