Hypothalamic-pituitary-adrenal axis tonus is associated with hippocampal microstructural asymmetry

► We studied the relationship between cortisol levels and hippocampus microstructure. ► Indices of grey matter microstructure were obtained using diffusion-tensor imaging. ► Higher left relative to right hippocampus MD was linked to higher cortisol levels. ► Associations were anatomically specific and not due to hippocampal volume asymmetry.