Home | Opinion | Link between cortisol levels in hair and stress from trauma: study

Link between cortisol levels in hair and stress from trauma: study

Recent research suggests important links between the experience of adversity, biology and mental health outcomes.

The study, published in the journal Psychoneuroendocrinology, examines the cortisol levels of 70 9-year-old Australian children. We recorded levels from head hair to determine total cortisol output over months. Cortisol is often referred to as the stress hormone. It plays a complex and wide-ranging role in the human stress and arousal response. We found that the number of traumatic events experienced earlier in childhood correlated with hair cortisol levels. The period of hair growth was measured after the events had occurred. These events commonly included illnesses and deaths in the family and being sick or hurt in an accident, rather than more serious types of trauma. Families were not selected for having experienced more trauma or adversity than others in the community.

What this work tells us is that the commonly experienced traumatic events of childhood probably alter hormonal and stress physiology in children in an enduring way. This also alters how children respond to their day-to-day experiences. Increasing evidence supports a role for hormones, such as cortisol and those related to puberty, in shaping children’s physiology and behaviour in response to their experiences. This is in part adaptive, an evolutionary mechanism to prepare children for what is to come later in life. However, a wealth of research also demonstrates that the experience of trauma and adversity increases risk for a range of negative health outcomes, including mental illness and behavioural problems (e.g., problematic drug use, risky sex) and physical health disorders (e.g., diabetes, and respiratory and cardiovascular problems). Indeed, we see dysregulated cortisol function in a range of mental health disorders, such as depression, anxiety and post-traumatic stress disorder.

So what should we conclude from this work? Does it suggest that the effects of trauma are irreversible? In short, no. The traumatic events we studied explained only about 10 per cent of the variance in children’s long-term cortisol levels. This study is the first part of an ongoing longitudinal investigation and future work will elucidate relationships between cortisol in hair and later health outcomes. We all experience traumatic events in our lives; however, most people will not develop a mental health disorder. In other research we have conducted, we have found that other factors, such as parental warmth in childhood, influence brain development and decrease risk of depression and anxiety disorders through adolescence. Our work to date demonstrates the influence of the environment, both good and bad, on children’s health outcomes, but also, and critically, that children’s biology is both sensitive and malleable.

Dr Julian G. Simmons is a research fellow in child and adolescent mental health at the University of Melbourne, and is based in the Melbourne School of Psychological Sciences and the Melbourne Neuropsychiatry Centre.

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