IGF1 and schizophrenia: The subgroup in which peripheral IGF‐1 levels were measured in plasma (Demirel et al., 2014; Palomino et al., 2013) was without any heterogeneity (I2 = 0.00%) in the meta‐analysis where schizophrenia patients were under antipsychotic treatment, but the combined effect size was nonsignificant (Hedges’ g 0.03, 95% CI from −0.02 to 0.08).