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.

旨在减少 COVID-19 传播的封锁政策显示出意想不到的心理健康后果；然而，自然环境可以为患有抑郁症或焦虑症的人提供喘息的机会。以前的横断面文献报告了 COVID-19 大流行期间户外暴露对心理健康的保护作用。我们纵向评估绿色运动是否与不良心理健康症状的减少相对应，同时控制了国家封锁政策。我们还检查了这种关系是否因州锁定状态而异。作为我们的暴露变量，我们指定了参与户外散步、慢跑或远足（绿色运动）。我们使用 4 项患者健康问卷 (PHQ-4) 作为结果变量来测量焦虑和抑郁症状。我们利用了了解美国研究 (UAS)，在 2020 年 3 月 10 日至 2021 年 5 月 26 日期间每两周对美国 50 个州的 8253 名成年人进行全国代表性样本调查。线性固定效应分析控制了不随时间变化的个人因素，以及就业状况和家庭收入。回归结果表明，作为绿色运动的函数，PHQ-4 分数略有下降，约为 0.10（较少的心理健康症状），控制了状态锁定状态。我们还发现，在国家封锁政策期间，绿色运动对心理健康症状的保护作用略大。此外，我们发现，与室内运动相反，绿色运动与锁定期间 PHQ-4 分数的下降相对应。与大自然接触可能会改善情绪并减少心理健康症状，尤其是在 COVID-19 大流行等压力诱发时期。