The associations of glycosylated hemoglobin with grey matter volume and depression: Investigating mediating role of grey matter volume

•This is the first study to investigate the mediation effect of GMV on the association between HbA1c and depression.•Hba1c was negatively associated with GMV, and that association were stronger in prediabetic participants.•Cerebral GMV plays a mediating role on the association “HbA1c-depression”, with a proportions of 6.82%.•Effective control of glycemia can potentially prevent brain abnormality and reduce the risk of depression.