Simple Hair Test Detects High Stress in Children with Chronic Illness

A groundbreaking study has revealed that a simple hair test can identify high stress levels in children living with chronic illnesses. Researchers at the University of Waterloo in Canada found that measuring cortisol, a stress hormone stored in hair, may help pinpoint young patients at risk of developing anxiety, depression, or behavioral issues.

According to a 2025 study, approximately one in four children globally lives with a chronic illness, with prevalence estimates ranging from 10% to 30%. Chronic physical illnesses (CPI) such as type 1 diabetes, juvenile arthritis, and epilepsy present significant challenges, not just in managing symptoms but also in maintaining mental well-being.

Emma Littler, a PhD candidate in Public Health Sciences and the lead author of the study, explained, “Living with a chronic illness means facing daily challenges such as taking medications, missing school, and adjusting activities, all of which can take a serious emotional toll.” The study’s findings indicate that prolonged high stress, as measured through hair samples, could facilitate earlier identification of children with CPIs who are most vulnerable to mental health problems.

Understanding Cortisol and Its Implications

Cortisol is produced by the adrenal glands and plays a crucial role in the body’s response to stress, regulating functions such as blood sugar, blood pressure, and sleep cycles. As hair grows steadily—about 1 cm (0.4 in) per month—it serves as a timeline of cortisol exposure. A 1-cm segment of hair represents approximately one month of stress exposure, while a 3-cm segment reflects around three months.

The study involved 244 children aged two to 16 with a CPI, tracked over a period of 48 months. Hair samples were collected up to five times during this period, with researchers examining cortisol levels to identify different patterns or “trajectories.”

The analysis categorized cortisol patterns into three groups:
1. **Hypersecretion** (68%) – consistently high cortisol levels
2. **Hyposecretion** (9%) – consistently low cortisol levels
3. **Hyper-to-hypo** (23%) – initially high cortisol levels that decreased to normal

Children in the hyper-to-hypo group exhibited fewer mental health issues compared to those in the hypersecretion category. Interestingly, children classified in the hyposecretion group did not display significant differences in mental health symptoms when compared to those with chronically high cortisol levels.

Overall, high cortisol levels appeared closely linked to an increased risk of mental health problems, aligning with previous research on the harmful effects of stress. Other factors, such as higher disability scores and certain parental characteristics, were also associated with worse mental health outcomes.

Future Implications for Intervention

Despite its promising findings, the study does have limitations. Most participants were White and came from relatively advantaged backgrounds, limiting the generalizability of the results. Additionally, the absence of a healthy control group means comparisons were indirect, and the effects of puberty were not measured across the broad age range of participants.

Nonetheless, tracking hair cortisol levels over time may prove invaluable in identifying children at higher risk of developing mental health issues. The study also suggests that mindfulness-based interventions could effectively lower cortisol levels and improve outcomes for affected children.

Dr. Mark Ferro, a co-author and associate professor in the School of Public Health Sciences at the University of Waterloo, emphasized the importance of early identification of risk factors. “Identifying these risk factors early could help doctors and families intervene before emotional and behavioral difficulties take hold,” he noted.

The findings were published in the journal Stress and Health, and they underline the potential of hair cortisol as a non-invasive biomarker that could be used to screen children and monitor the effectiveness of treatments or support programs aimed at reducing stress.