Changes in hair cortisol in a New Zealand community sample during the Covid-19 pandemic

Background: Evidence suggests that countries with higher Covid-19 infection rates experienced poorer mental health. This study examined whether hair cortisol reduced over time in New Zealand, a country that managed to eliminate the virus in the first year of the pandemic due to an initial strict lockdown. Methods: A longitudinal cohort study assessed self-reported stress, anxiety and depression and collected hair samples that were analyzed for cortisol, across two waves in 2020. The sample consisted of 44 adults who each returned two 3 cm hair samples and completed self-reports. Hair cortisol was assessed per centimetre. Results: Hair cortisol reduced over time (F (5, 99.126) = 10.15, p <.001, partial eta squared = 0.19), as did anxiety and depression. Higher hair cortisol was significantly associated with more negative life events reported at wave two (r = 0.30 segment 1, r = 0.34 segment 2, p <.05), but not anxiety or depression. Conclusions: Strict virus control measures may not only reduce infection rates, but also reduce psychological distress, and hair cortisol over time.