New Clues About the Antidepressant Power of Aerobic Exercise

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Aerobic exercise is widely recognized for its antidepressant potential. Over the past three decades, countless human and animal studies have identified the ability of regular aerobic workouts to reduce depression-like symptoms and offset someone's risk of becoming depressed. (See here, here, here, here)

Last week, a systematic review (Hu et al., 2020) published on Aug. 18 in the journal BMC Public Health concluded: "The evidence from this [review] suggests that exercise interventions have a beneficial effect on depressive symptoms in the general population across a wide age-range."

This week, a new study (Brush et al., 2020) led by researchers at Rutgers University adds to the growing body of evidence showing that "aerobic exercise has demonstrated antidepressant efficacy among adults with major depression." These findings were published on Aug. 24 in the journal Psychological Medicine.

What makes this "precision medicine" research unique is that it also examines how neural indicators of reward-related brain activity and cognitive control at baseline may help to predict the likelihood of someone with major depressive disorder (MDD) benefiting from eight weeks of moderate-intensity aerobic exercise (three times per week).

For this randomized study, the researchers recruited 66 young adults (average age = 20.23 years) who had been clinically diagnosed with major depression. Then, about half of the study participants (n = 35) were randomly assigned to perform eight weeks of moderate-intensity aerobic exercise three times a week; the other cohort (n = 31) didn't do any cardio but performed light-intensity stretching exercises with the same weekly frequency. Depressive symptoms were assessed before, during, and after these eight weeks.

Additionally, the researchers used event-related brain potential to assess reward processing [reward positivity (RewP)] and cognitive control [error-related negativity (ERN)] before and after the light-stretching and moderate-intensity aerobic exercise interventions

There are two main takeaways from this study. First, the researchers conclude that aerobic exercise resulted in a greater reduction of depressive symptoms than light-intensity stretching alone. On average, depression symptoms were reduced by 55 percent in the moderate-intensity aerobic exercise cohort and by 31 percent in the "no-cardio, stretch-only" group.

The second notable finding from this precision medicine study is that participants with more robust reward positivity (RewP) and more severe depressive symptoms when the study began were more likely to respond to aerobic exercise as a potential treatment for clinical depression. "In the aerobic exercise group, individuals with a larger pre-treatment RewP and increased baseline depressive symptom severity were more likely to respond to an aerobic exercise program," the authors explain.

Based on these findings, the authors conclude: "Aerobic exercise effectively alleviates depressive symptoms in adults with major depression, particularly for those with increased depressive symptom severity and a larger reward positivity at baseline."

This study has some limitations. "Our study needs to be replicated, but the precision medicine approach of predicting who may or may not benefit from exercise as an antidepressant is provocative," senior author Brandon Alderman said in a news release. "We also need to know whether exercise has a similar antidepressant effect in younger adolescents and in adults with more treatment-resistant forms of depression who have not responded well to traditional treatments, including antidepressants and cognitive behavioral therapy."

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