Using a longitudinal dataset linking biometric and survey data from several cohorts of young adults before and during the COVID-19 pandemic (N=682), we document large disruptions to physical activity, sleep, time use, and mental health. At the onset of the pandemic, average steps decline from 10,000 to 4,600 steps per day, sleep increases by 25 to 30 min per night, time spent socializing declines by over half to less than 30 min, and screen time more than doubles to over 5 h per day. Over the course of the pandemic from March to July 2020 the proportion of participants at risk for clinical depression ranges from 46% to 61%, up to a 90% increase in depression rates compared to the same population just prior to the pandemic. Our analyses suggest that disruption to physical activity is a leading risk factor for depression during the pandemic. However, restoration of those habits through a short-term intervention does not meaningfully improve mental well-being.

COVID-19 has affected daily life in unprecedented ways. Using a longitudinal dataset linking biometric and survey data from several cohorts of young adults before and during the pandemic (N=685), we document large disruptions to physical activity, sleep, time use, and mental health. At the onset of the pandemic, average steps decline from 9,400 to 4,600 steps per day, sleep increases by about 25-30 minutes per night, time spent socializing declines by over half to less than 30 minutes, and screen time more than doubles to over 5 hours per day. The proportion of participants at risk of clinical depression increases to 65%, over twice the rate in the same population prior to the pandemic. Our analyses suggest that disruption to physical activity is a leading risk factor for depression during the pandemic. However, restoration of those habits-either naturally or through policy intervention-has limited impact on restoring mental well-being. * Following the norms of Economics, authorship is alphabetical. All authors contributed to the project equally. We thank Ben Schenck and William Wang for excellent research assistance

The rapid evolution into a 24 h society challenges individuals' ability to conciliate work schedules and biological needs. Epidemiological research suggests that social and biological time are increasingly drifting apart ("social jetlag"). This study uses a spatial regression discontinuity design to estimate the economic cost of the misalignment between social and biological rhythms arising at the border of a time-zone in the presence of relatively rigid social schedules (e.g., work and school schedules). Exploiting the discontinuity in the timing of natural light at a time-zone boundary, we find that an extra hour of natural light in the evening reduces sleep duration by an average of 19 minutes and increases the likelihood of reporting insufficient sleep. Using data drawn from the Centers for Disease Control and Prevention and the US Census, we find that the discontinuity in the timing of natural light has significant effects on health outcomes typically associated with circadian rhythms disruptions (e.g., obesity, diabetes, cardiovascular diseases, and breast cancer) and economic performance (per capita income). We provide a lower bound estimate of the health care costs and productivity losses associated with these effects.

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