The impact of social distancing on mental health during the Covid-19 pandemic: A nationwide study of 4.6 million Danish adults

Background: Current knowledge on psychiatric illness following periods of social distancing during the COVID-19 pandemic is mostly limited to smaller studies in selected populations. This nationwide study of all 4.6 million Danish adults examined if periods of social distancing were associated with changes in surrogate measures of mental health. Methods: All Danish adults (. 18 years) were included and rates of collection of antidepressant prescriptions, psychiatric hospital admission and suicide or suicide attempt for the periods March 12, 2020 . May 20, 2020 (lockdown period 1), and December 21, 2020 . March 1, 2021 (lockdown period 2), were compared to corresponding periods one year prior. Individuals were censored due to death or SARS-CoV-2 infection. Results: Rates of antidepressant consumption were increased for both period 1 and 2, with an IRR of 1.02 (95% CI 1.01-1.02, p < 0.001) and IRR of 1.08 (95% CI 1.08-1.09, p < 0.001), respectively, compared to the control periods. Rates of psychiatric hospital admissions decreased significantly with an IRR of 0.65 (95% CI 0.63-0.66, p < 0.001) for period 1 and 0.86 (95% CI 0.84-0.88 p < 0.001) for period 2. The risk of suicide was not increased in period 1, IRR 0.96 (95% CI 0.82-1.13, p = 0.64), but seemed increased in period 2, IRR 1.19 (95% CI 1.02-1.38, p = 0.03). Conclusion: Periods of social distancing during Covid-19 were associated with a small but significant increased consumption of antidepressants but a decreased incidence of psychiatric hospitalization. Suicide-risk seemed increased in the second lockdown period.