Hair cortisol concentration (HCC) decreased significantly over two years in adolescent twins, with limited associations with psychosocial stressors, suggesting HCC 'may capture specific stress-related processes in certain subgroups' rather than functioning as 'a broadly sensitive biomarker of chronic stress.'
Key Findings
Results
Average hair cortisol concentration decreased significantly between the two assessment sessions approximately two years apart.
Sample consisted of 302 community-dwelling adolescent twins from Brisbane, Australia
Data collected at two sessions approximately two years apart following a standardised assessment protocol
Three cm long hair samples were analysed to quantify cumulative stress exposure over three months
Linear mixed-effects models were used to examine mean-level associations
Results
There was no main effect of sex, twin zygosity, or pubertal stage on average hair cortisol concentration.
Sex, twin zygosity, and pubertal stage were examined as predictors of HCC
None of these variables showed a statistically significant main effect on average HCC
Linear mixed-effects models were used for analysis
The sample included both male and female adolescent twins of varying zygosity
Results
In males, higher average HCC at the second session was associated with elevated general anxiety.
This sex-specific association was found only at the second assessment session
Participants completed self-reported measures of anxiety
The association was identified using linear mixed-effects models
No equivalent anxiety association was found in females
Results
In females, higher average HCC was associated with higher exposure to severe lifetime stress.
This association was specific to female participants
Participants completed self-reported measures of daily stress and adverse childhood experiences (ACEs)
The association was with severe lifetime stress specifically, not ACEs
No equivalent severe lifetime stress association was found in males
Results
No associations were found between average HCC and adverse childhood experiences (ACEs).
ACEs were measured via self-report in all participants
Neither linear mixed-effects models nor quantile regression revealed significant associations between HCC and ACEs
This null finding held across the sample regardless of sex
Both mean-level and distributional analyses (quantile regression) were employed to examine this association
Results
HCC provided a stable measure of long-term cortisol in adolescents, though its associations with psychosocial stressors were limited in this cohort.
HCC reflects cumulative cortisol secretion over the three months before each assessment
The authors characterise average HCC as 'a stable measure of long-term cortisol in adolescents'
Associations with depression, daily stress, and social support were not highlighted as significant findings
The authors conclude that 'its utility may depend on the type, timing, and chronicity of stress exposure'
Methods
Quantile regression was used alongside linear mixed-effects models to examine distributional associations between HCC and psychological and environmental variables.
Quantile regression examined associations across the distribution of HCC rather than only at the mean
Psychological measures included depression, anxiety, daily stress, social support, and ACEs
This dual analytical approach allowed examination of both mean-level and distributional associations
The study is described as longitudinal with a standardised assessment protocol