IGF1 and schizophrenia: In patients with schizophrenia, we found a significant positive correlation between serum cortisol levels and BPRS scores (R = 0.38, p < 0.01; Fig. 3A) and a significant negative correlation between serum IGF-1 levels and BPRS scores (R = − 0.50, P < 0.01; Fig. 3B).