By Gary L. Wenk, Professor of  Psychology, Neuroscience and Molecular Virology, Ohio State University

Depression is an expected consequence of any pandemic. Being isolated alone at home, away from routine and friends, can make the situation worse.

Getting out of the house to talk to the neighbors or walk your dog have become necessary behaviors to maintain good mental health. For some people, who are more vulnerable to becoming depressed, the isolation required to slow the progression of this virus may have far more negative consequences. Can exercise help these susceptible people? 

The effects of exercise on depressed individuals have been investigated extensively. Too often, the conclusions drawn from these studies in the popular press or social media have gone beyond what the actual data can defend. Past studies have numerous fatal flaws that undermine confidence in their results.

Previous studies have varied wildly in size, type of control group, methodological rigor, length of follow-up, and even the type of exercise modality. Randomized trials of exercise have generally ranged in length from six weeks to four months and typically emphasized aerobic exercise, although some studies on resistance training also have been conducted. The many differences in study design have contributed to the current level of confusion and misunderstandings about the benefits of exercise on depression. 

Although many trials have been conducted on adults with major depressive disorder, only a few used high-quality methodologies in which the treatment allocation was concealed. Many of the other studies failed to comply with the standard intention-to-treat analyses. This means that the final analysis included every subject who was assigned a randomized treatment. This type of analysis ignores noncompliance (the subjects exercised too much or not at all), protocol deviations (they performed the wrong exercise), withdrawal from the study, or any of a number of potential things that might have happened to the subjects after they had been assigned to their study groups.

The general problem is, it is very difficult to convince human subjects to exercise consistently without introducing their own creative changes that often undermine the integrity of the study. The results of many past studies were made difficult to analyze because they failed to include a control group in the design. Sometimes the most important variable, the degree of depression experienced by the subjects, was assessed by someone who was not blinded to treatment. Thus, the studies were vulnerable to experimenter bias and were unreliable. Unfortunately, that has not stopped some pundits from referencing them.

For all of these reasons, the initial enthusiasm and many outrageously positive claims about the effectiveness of exercise in combating depression have not been supported by newer studies. Recent well-controlled studies have found only a “modest to moderate” antidepressant effect due to daily exercise.

In studies that used a standard head-to-head comparison, exercise was no better or worse than standard cognitive behavioral therapy for treating depression—that is, just talking to someone, hopefully from a safe distance, was as effective as exercising. When researchers compared the effectiveness of exercise on adults who were given a standard antidepressant drug therapy, they found no significant benefit of one approach over another.

Overall, the benefits of physical exercise for depression are subtle but real. Our most recent and largest studies clearly demonstrate that although exercise is not better than drugs, it should be considered as an important adjunct therapy to any treatment plan for depressed patients during these very difficult times.

Gary L. Wenk is Professor of Psychology & Neuroscience & Molecular Virology, Immunology and Medical Genetics at the Ohio State University and Medical Center. He is the author of “Your Brain on Food” (3rd Edition, 2019, Oxford University Press)