Green exercise, mental health symptoms, and state lockdown policies: A longitudinal study.

Lockdown policies aimed at decreasing the transmission of COVID-19 showed unintended mental health consequences; however, natural settings may offer a respite for individuals suffering from depression or anxiety symptoms. Previous cross-sectional literature reports protective effects of outdoor exposure on mental health during the COVID-19 pandemic. We longitudinally assess whether green exercise corresponded with a decline in adverse mental health symptoms, controlling for state lockdown policies. We also examine whether the relation differed by state lockdown status. As our exposure variable, we specificized participation in an outdoor walk, jog, or hike (green exercise). We used, as the outcome variable, the 4-item Patient Health Questionnaire (PHQ-4) to measure anxiety and depression symptoms. We utilized the Understanding America Study (UAS), a nationally representative sample of 8253 adults across 50 states in the US, surveyed biweekly between March 10, 2020-May 26, 2021. Linear fixed effect analyses controlled for time-invariant individual factors, as well as employment status, and household income. Regression results indicate a modest decline in PHQ-4 scores of approximately 0.10 (less mental health symptoms) as a function of green exercise, controlling for state lockdown status. We also find a slightly greater protective effect of green exercise on mental health symptoms during state lockdown policies. Additionally, we find that green exercise, as opposed to indoor exercise, corresponds with a decrease in PHQ-4 scores during lockdown. Contact with nature may improve mood and decrease mental health symptoms, especially during stress-inducing periods such as the COVID-19 pandemic. Green exercise as a recommended behavioral intervention may hold relevance for greater public health.