The purpose of the present study was to address 1) whether exercise provides protection against new-onset depression and anxiety and 2) if so, the intensity and amount of exercise required to gain protection and, lastly, 3) the mechanisms that underlie any association.

A “healthy” cohort of 33,908 adults, selected on the basis of having no symptoms of common mental disorder or limiting physical health conditions, was prospectively followed for 11 years. Validated measures of exercise, depression, anxiety, and a range of potential confounding and mediating factors were collected.

Undertaking regular leisure-time exercise was associated with reduced incidence of future depression but not anxiety. The majority of this protective effect occurred at low levels of exercise and was observed regardless of intensity. After adjustment for confounders, the population attributable fraction suggests that, assuming the relationship is causal, 12% of future cases of depression could have been prevented if all participants had engaged in at least 1 hour of physical activity each week. The social and physical health benefits of exercise explained a small proportion of the protective effect. Previously proposed biological mechanisms, such as alterations in parasympathetic vagal tone, did not appear to have a role in explaining the protection against depression.

Regular leisure-time exercise of any intensity provides protection against future depression but not anxiety. Relatively modest changes in population levels of exercise may have important public mental health benefits and prevent a substantial number of new cases of depression.

本研究的目的是要解决1）运动是否可提供针对新发抑郁症和焦虑症的保护，以及2）如果是这样，获得保护所需的运动强度和运动量，最后，3）构成任何关联基础的机制。

前瞻性随访了11年，该研究以33,908名成年人的“健康”队列为基础，该队列是根据没有常见精神障碍症状或身体健康状况受到限制而选择的。收集了经过验证的运动，抑郁，焦虑以及一系列潜在的混淆和中介因素的量度。

定期进行休闲运动与减少未来抑郁症的发生率有关，但与焦虑症没有关系。这种保护作用的大部分发生在低运动量下，无论强度如何，都可以观察到。在对混杂因素进行调整之后，人口可归因分数表明，假设这种关系是因果关系，如果所有参与者每周至少参加1小时的体育锻炼，则本可以预防12％的未来抑郁症病例。运动对社会和身体健康的好处解释了保护作用的一小部分。先前提出的生物学机制，如副交感神经迷走神经音调的改变，似乎在解释预防抑郁症方面没有作用。

定期进行任何强度的休闲时间锻炼都可以防止日后抑郁，但不能缓解焦虑。人口运动水平的相对适度变化可能会带来重要的公共精神健康益处，并预防大量新的抑郁症病例。