Background: How population mental health has evolved across the COVID-19 pandemic under varied lockdown measures is poorly understood, with impacts on health inequalities unclear. We investigated changes in mental health and sociodemographic inequalities from before and across the first year of the pandemic in 11 longitudinal studies. Methods: Data from 11 UK longitudinal population-based studies with pre-pandemic measures of psychological distress were analysed and estimates pooled. Trends in the prevalence of poor mental health were assessed across the pandemic at three time periods: initial lockdown (TP1, Mar-June 20); easing of restrictions (TP2, July-Oct 20); and a subsequent lockdown (TP3, Nov 20-Mar 21). Multi-level regression was used to examine changes in psychological distress compared to pre-pandemic; with stratified analyses by sex, ethnicity, education, age, and UK country. Results: Across the 11 studies (n=54,609), mental health had deteriorated from pre-pandemic scores across all three pandemic time periods (TP1 Standardised Mean Difference (SMD): 0.13 (95% CI: 0.03, 0.23); TP2 SMD: 0.18 (0.09, 0.27); TP3 SMD: 0.20 (0.09, 0.31)). Changes in psychological distress across the pandemic were higher in females (TP3 SMD: 0.23 (0.11, 0.35)) than males (TP3 SMD: 0.16 (0.06, 0.26)), and slightly lower in below-degree level educated persons at some time periods (TP3 SMD: 0.18 (0.06, 0.30)) compared to those who held degrees (TP3 SMD: 0.26 (0.14, 0.38)). Increased distress was most prominent amongst adults aged 35-44 years (TP3 SMD: 0.49 (0.15, 0.84)). We did not find evidence of changes in distress differing by ethnicity or UK country. Conclusions: The substantial deterioration in mental health seen in the UK during the first lockdown did not reverse when lockdown lifted, and a sustained worsening is observed across the pandemic. Mental health declines have not been equal across the population, with females, those with higher degrees, and younger adults more affected.
Psychological Distress Before and During the COVID-19 Pandemic: Sociodemographic Inequalities in 11 UK Longitudinal Studies