Sociodemographic, lifestyle, and psychosocial determinants of hair cortisol in a South London community sample

Objective Hypothalamic–pituitary–adrenal (HPA) measures are crucial for research into stress and stress-related disorders. Most HPA measures fluctuate depending on diurnal rhythms and state confounders. Hair cortisol concentrations (HCC) are less susceptible to such fluctuations, but less is known about trait-like confounders. Using a community sample, we tested the relationship between HCC and a range of variables including demographic variables, hair treatment, and medication, as well as psychosocial variables, namely childhood trauma, critical life events, and depressive symptoms. Methods Hair samples were collected from 144 individuals from the South East London Community Health (SELCoH) study. Childhood trauma, life events, and depressive symptoms were measured, together with age, sex, ethnicity, relationship status, educational attainment, employment status, occupational social class, hair washing frequency, hair treatments, season reflected in the hair sample, hazardous drinking, smoking, medication intake, and body mass index. Hair samples reflecting the past 3 months were collected and analysed using immunoassays. First, correlations (continuous variables) and simple linear regressions (dichotomous variables) were conducted to identify sociodemographic, hair-related, and lifestyle determinants of HCC. Next, multiple linear regressions were conducted to test the relationship between psychosocial variables and HCC when controlling for the identified confounders. Results Age (r = −0.17, p = 0.050), White British ethnicity (β = −0.19, p = 0.023), heat-based treatments (β = −0.22, p = 0.010), and winter season (β = −0.18, p = 0.024) were associated with lower HCC, whereas summer season (β = 0.24, p = 0.024), painkillers (β = 0.25, p = 0.003), anxiolytics/antidepressants (β = 0.21, p = 0.014), and hormonal contraceptives (β = 0.27, p = 0.006) were associated with higher HCC. Controlling for these confounders, physical neglect during childhood (β = −0.17, p = 0.057), war-related experiences (β = 0.20, p = 0.027), separation (β = 0.18, p = 0.054), and being the victim of a serious crime (β = −0.17, p = 0.062) were linked with altered HCC. Conclusion Our findings suggest that variation in HCC occurs according to sociodemographic, hair-related, and lifestyle variables, and that certain associations between stress and altered HCC can only be revealed when accounting for these confounders