Cortisol is a well-known stress hormone and until recently, we have only been able to understand how stressed a person has been for about the past 20 minutes or the past day. Now, with about 100 strands of hair clipped from the scalp, we can get a biological indicator of stress over the past three months. Since hair growth approximately 1 cm per month, with 3 cms, we capture cortisol retrospectively, so we can measure "chronic" or accumulated stress. In one of our first studies of chronic stress conducted on the University of Massachusetts, Boston campus, we included students, staff, and community members.
The present research was conducted to assess relationships between biological chronic stress as measured by CORT and perceived stress indices. Furthermore, this research examines potential differences in biological and perceived stress by racial/ethnic identity, SES, sex and age. We obtained domain-specific indices of stress (i.e. personal perceived stress, chaos in the home and neighborhood assessments) and examined associations between CORT, subjective stress and health indicators [blood pressure and waist-to-hip ratio (WHR)]. Finally, we also investigated the interactions of well-known factors associated with health disparities: racial/ethnic identity and SES with both hair CORT and the perceived stress indices as the dependent variables.
We found the highest cortisol levels in males, the group aged 18-22 (the entire sample was 18-66 yrs.), and those who identified as an ethnic minority. Critically, we also found perceived stress was positively related to hair cortisol. Specifically, when an individual was higher across several domains of stress (e.g., stress at home, stress in their neighborhood); this was associated with higher secretion of the stress hormone. One important interpretation of this is that perceiving something as stressful, whether happening or not, can be just as meaningful on our biological reactions to stress.
An unanticipated finding was that hair cortisol levels were higher for minorities in the higher socioeconomic status (SES). Much of the literature examining the SES/health gradient posits that better health is associated with higher objective and subjective status. However, there is related evidence that minority members may not always be conferred this benefit. One interpretation is that minorities in higher SES experience greater, albeit more subtle discrimination. Researchers suggest that in high SES, race becomes more salient, along with greater instances of misunderstanding cultural differences and awkwardness during interactions.
Interestingly, CORT was associated with only one of the other biomarkers of stress, higher systolic blood pressure. Waist and WHR were not significantly associated with CORT in these data. This was unexpected, since WHR is a well-known indicator of allostatic load and has been positively associated with CORT in other research (e.g.Manenschijn, et al., 2011). The relationship between CORT and health risk indicators needs further investigation. It is not yet known whether CORT will be consistently associated with chronic health issues and reliably predictive of chronic diseases associated with allostatic load.
Since hair grows approximately 1 cm per month, capturing 3 cms of hair (about 75-100 strands) can give us a retrospective window of stress levels for the past 3 months, rather than moments or days. Hair cortisol is a promising measure of cumulative or long term stress stress. And chronic stress is quickly becoming recognized as the mediator for multiple psychological and physical health outcomes.