Schizophrenia patients under antipsychotic treatment had significantly lower peripheral IGF‐1 levels compared to healthy controls (n = 632, Hedges’ g –0.42, 95% CI from –0.79 to –0.04, p = .006, I2 = 70.38%), while no significant difference was found between schizophrenia patients regardless of the antipsychotic treatment status and healthy controls, as well as between antipsychotic naïve or free schizophrenia patients and healthy controls, and before and after initiation of antipsychotic treatment. This evidence concerns the gene IGF1 and schizophrenia.