Cortisol levels are positively correlated with hippocampal N-acetylaspartate

Background This study examined the relationship of hypothalamic–pituitary–adrenal measures and hippocampal N-acetylaspartate (NAA) in posttraumatic stress disorder (PTSD) patients and control subjects. Methods Eleven patients with combat-related PTSD and 11 control subjects were evaluated with magnetic resonance spectroscopy as well as by morning salivary cortisol samples before and after administration of low-dose dexamethasone (.5 mg). Results Left hippocampal NAA was strongly associated with both pre-dexamethasone cortisol levels (n = 22, r = .53, p = .013) and post-dexamethasone cortisol levels (n = 22, r = .63, p = .002). After accounting for clinical symptom severity and hippocampal volume, cortisol levels accounted for 21.9% of the variance (F = 5.6, p = .004) in left hippocampal NAA and 12.6% of the variance (F = 3.2, p = .035) in right hippocampal NAA. Conclusions This study shows a positive relationship between cortisol levels and hippocampal NAA in subjects without hypercortisolemia. Within the range of values seen in our subjects, cortisol may have a trophic effect on the hippocampus.