As the COVID-19 pandemic enters its second year, new fast-spreading variants have caused a surge in infections in many countries, and renewed lockdowns. The devastation of the pandemic — millions of deaths, economic strife and unprecedented curbs on social interaction — has already had a marked effect on people’s mental health. Researchers worldwide are investigating the causes and impacts of this stress, and some fear that the deterioration in mental health could linger long after the pandemic has subsided. Ultimately, scientists hope that they can use the mountains of data being collected in studies about mental health to link the impact of particular control measures to changes in people’s well-being, and to inform the management of future pandemics.