It’s all in the hair: Changes in hair cortisol concentrations in reaction to the COVID-19 pandemic predicts post-traumatic stress symptoms in children

BACKGROUND: About 25 to 35% of victims of a traumatic event will develop post-traumatic stress disorder (PTSD). Low cortisol levels appear to be a risk factor for the development of PTSD. In adults, decreased diurnal and cumulative cortisol levels before or shortly after a traumatic event are associated with increased post-traumatic symptoms in the months thereafter. In contrast, results from the only two studies conducted in children showed that elevated diurnal cortisol levels shortly after exposure to a traumatic event are associated with more severe post-traumatic symptomatology. Given that a pandemic can induce post-traumatic stress symptoms, we investigated whether cumulative cortisol levels prior to and in the beginning stages of the COVID-19 pandemic in Quebec (Canada) predicted post-traumatic stress symptoms in children. METHODS: We collected hair samples from 69 children (8-12 y/o) without history of psychopathology and exposure to a traumatic event. Cortisol levels were measured before (December 2019 - February 2020) and at the beginning of the pandemic (March 2020 - May 2020). Post-traumatic stress symptoms were assessed every 3 months between June 2020 (T1) and March 2021 (T4). RESULTS: The results showed that the percentage change in cumulative cortisol levels between the beginning of and prior to the pandemic predicted post-traumatic stress symptoms at T1. Specifically, a decrease in cortisol levels early in the pandemic was associated with increased post-traumatic stress symptoms. CONCLUSION: This study suggests that a decrease in cortisol in response to a stressful event may be a predisposing factor for PTSD in children.