Chronic stress, salivary cortisol response, interpersonal relatedness, and depression among community-dwelling survivors of traumatic brain injury.

Depression is a common mood disorder after traumatic brain injury (TBI). Largely, study of this phenomenon is theoretical and without biological measures. This explanatory study, guided by McEwen's allostasis model of stress, examined relationships among chronic stress, salivary cortisol profiles, post-injury depression, and interpersonal relatedness. Seventy-five participants, who were or had participated in outpatient brain injury rehabilitation therapies and experienced mild-to-moderate levels of brain injury, were recruited for this cross-sectional study. Salivary cortisol levels showed the usual patterns of circadian rhythmicity, and those with milder injuries had higher 8 am cortisol levels. Salivary cortisol values were not related to measures of chronic stress, interpersonal relatedness, or depression with two exceptions. The 8 am and noon mean values were significantly greater for those who reported more pre-injury childhood adversity, while the 8 pm cortisol mean level was associated with the frequency of pre-injury stressful life events. For this outpatient sample, salivary cortisol levels do not appear to be elevated after TBI or to lack circadian rhythmicity as previously reported. There may be some value in using this measure as a correlate with persons treated in specialized TBI clinics who report pre-injury chronic stress, but future studies are needed with TBI persons who were not treated in specialized clinics or were not taking medications known to influence the hypothalamic-pituitary-adrenal axis.