The role of personality and traumatic events in cortisol levels - Where does PTSD fit in?

Background: Studies of cortisol in post-traumatic stress disorder (PTSD) have yielded mixed results. We hypothesize that personality traits and traumatic experiences could be the confounders of cortisol measures and disease symptoms. Method: This study was a part of a broader project in which simultaneous psychological and biological investigations were carried out in hospital conditions on 400 male participants categorized by four groups: (A) 133 with current PTSD, (B) 66 with lifetime PTSD, (C) 102 trauma controls, and (D) 99 healthy controls (matched by age and education). Cortisol and ACTH were measured in blood samples taken hourly from 22:00 h to 09:00 h, with an additional sample at 07:30 h (resting state and morning rise). The next night, dexamethasone (0.5 mg) suppression test was performed. Results: No significant differences in basal cortisol and ACTH were found between study groups. The trait Conscientiousness, negatively modulated by Extraversion (assessed by NEO Personality Inventory-Revised) was found to correlate with cortisol (but not with ACTH). Group differences are found on suppression. Structural equation modeling shows excellent fit only when the paths (influences) from Conscientiousness to basal cortisol and from traumatic events to suppression are present. The paths connecting suppression and PTSD symptoms do not contribute. Conclusions: Two sources of differences of hypothalamo-pituitary-adrenocortical axis functioning are implied, both only indirectly connected to PTSD. It seems that basal cortisol secretion is associated more tightly with personality (introvertively modulated Conscientiousness), while the regulation by glucocorticoid receptor system is sensitized by repeated traumatic situations