APOE and type 2 diabetes mellitus: Consequently, the loss of interhemispheric hippocampal asymmetry has emerged as a key contributor to cognitive decline and putative biomarker across various neurologic and neuropsychiatric conditions, including type 2 diabetes [17] carriage of the ApoE ɛ4 allele [18], as well as in BD [19] and MDD [20].