A systematic review of abnormalities in intracortical myelin across psychiatric illnesses

•Braining imaging studies showed intracortical myelin (ICM) abnormalities in schizophrenia (SCZ), bipolar disorder (BD), major depressive disorder (MDD), and obsessive-compulsive disorder (OCD).•ICM deficits were present in the frontal lobe across all identified psychiatric illnesses, in the frontal gyri and insular regions of SCZ, and the temporal, parietal, and occipital cortices of BD and MDD.•Increased ICM was observed in the parietal and temporal cortices in SCZ and OCD.•Antipsychotic exposure in SCZ was linked to increased ICM, with higher sensitivity to injections versus oral administration.