Schizophrenia patients had significantly lower peripheral IGF‐1 levels compared to healthy controls (Hedges’ g −0.42, 95% CI from −0.79 to −0.04, Z = −2.73, p = .006), but between‐study heterogeneity was significant (Q = 20.26, p = .002, I2 = 70.38%). Here, IGF1 is linked to schizophrenia.