Exercise has long been recognized as an effective treatment for the depressed. However, most studies do not differentiate between indoor and outdoor physical activities. Environmental context is a classic confounding variable that, when controlled, can help to clarify any virtually any association being investigated.

A preliminary study led by Anika Fruehauf, that has been accepted for future publishing in the journal Mental Health and Physical Activity, directly addresses this information gap by focusing on the impact of setting on acute (immediate, short-term) benefits of exercise. It was discovered that outdoor activity appears to have a significantly improved effect on certain symptoms of depression when compared to the indoor alternative.

Participation in the study was completed by 14 inpatients at a mental health care facility with an existing diagnosis of clinical depression and exhibiting mild to moderate symptoms. Each participant took part in three different sessions (lasting 60 minutes a piece) over 2-week period. They cycled during the indoor session, walked in the outdoor session and also took part in a control session where they simply sat with the option to read and/or play board games. Measures of depressive symptoms, including activation of emotional affect, valence (positive or negative) of affect and mood variables, were obtained with surveys completed by participants before, during and after each session.

The study yielded several significant findings. Perceived activation was higher in the outdoor activity group than the indoor, as were activation related mood types. Outdoor exercise produced a significant change in post-session activation, but this was not evident with interior environments. A reduction in mood related excitement was also observable following outdoor exercise alone. Finally, outdoor physical activity led to larger reductions in depressive mood and fatigue when compared to the control group.

People with depression can benefit from exercise in virtually any setting. With the completion of this research, it is becoming apparent that outdoor settings may lead to larger acute gains when compared with indoor alternatives.

There are a variety of potential explanations for this effect. For the depressed who spend a lot of time indoors, a simple change in setting may reduce symptoms by eliminating a contextual variable (the interior environment) that has become associated with their personal experience of depression. Alternatively, the improvements may be a result of nature’s influence on mood. Given the largely uncontrolled and preliminary nature of this research, future studies will help to both verify and expand upon these findings.