Simple Hair Test Can Identify Children at High Risk for Depression and Anxiety

A groundbreaking study suggests that measuring stress levels through children’s hair could hold the key to early detection of anxiety and depression, especially among those living with chronic physical illnesses (CPI). Researchers at the University of Waterloo have found that hair cortisol a biological marker that reflects long-term stress could be a simple, non-invasive screening tool to identify at-risk children years before symptoms become visible. "Hair cortisol offers a non-invasive, easy-to-collect biomarker that could one day be used to screen children and track whether treatments or support programs are helping to reduce stress,” said Professor Mark Ferro from the School of Public Health Sciences at Waterloo.

The study, published in Stress and Health, followed 244 Canadian children with chronic physical conditions over a span of four years. Researchers discovered that more than two-thirds of participants had persistently high levels of cortisol in their hair. These elevated stress levels strongly correlated with emotional and behavioral difficulties, including anxiety and depression. Children whose cortisol levels declined over time showed fewer mental health issues compared to those whose levels remained high, highlighting the potential of hair cortisol as a predictor of mental well-being.

The method works by analyzing segments of hair to create a historical record of cortisol exposure. Since hair grows about one centimeter per month, a three-centimeter sample can give a picture of a child's stress levels over a three-month period. This method offers a more accurate long-term view than saliva or blood tests, which only measure short-term cortisol spikes. The hair is washed, pulverized, and processed with solvents like methanol to extract cortisol, which is then measured using high-precision lab techniques such as enzyme-linked immunoassay or liquid chromatography-mass spectrometry.

Chronic physical illness affects nearly 40 percent of children in Canada, a number that continues to grow. These children are already at higher risk for developing mental health issues anywhere from 20% to 50% compared to their healthy peers. These conditions often lead to reduced quality of life, increased healthcare use, and in severe cases, suicidal ideation. That’s why early identification of mental health risks is critical, especially when intervention can still make a significant difference.