Regular exercise helped improve self-reported mental health in the past month, according to a cross-sectional study of general-population survey respondents.
Compared with adults who did not engage in any form of exercise, those who did experienced around a 43.2% overall lower mental health burden per month, representing around 1.5 fewer days of poor mental health (W=7.42 × 1010, P<2.2 × 10-16), reported Adam Chekroud, PhD, of Yale University in New Haven in Connecticut, and colleagues.
This positive association between exercise and improved mental health was even more pronounced in those who had a previous diagnosis of depression, marked by an average of 3.75 fewer days of poor mental health per month (W=1.61 × 109, P<2.2 × 10-16), they wrote in Lancet Psychiatry.
The researchers found that all types of exercise were tied to improved mental health, while those who participated in popular team sports saw largest associated reduction in poor mental health days:
Team sports: 22.3% lower monthly mental health burden
Cycling: 21.6% lower
Aerobic/gym activities: 20.1% lower
In an accompanying commentary, Gary Cooney, MBChB, MRCPsych, of Gartnavel Royal Hospital in Glasgow, highlighted that one major drawback to this analysis was the placement of "mental health" into one category. He stated that "there is a presupposition that it is possible and appropriate to combine all the various mental disorders as a single entity in pursuing this research." In the same vein, he warned against people using "mental health" and "depression" as interchangeable concepts.
The authors noted that they searched PubMed for all papers in English published before March 18, 2018, using the search term "depression" or "depressive disorder, major" prior to embarking on the study.
Additionally, Cooney said it was "difficult to see the justification for this approach when these conditions differ greatly in their underlying causes, clinical presentation, and treatment. Dementia, substance misuse, and personality disorder, for example, are considered as distinct entities for research and clinical purposes; capturing them for study under the combined banner of mental health might not add a great deal to our understanding."
Furthermore, Cooney criticized the use of self-reported patient data used for the analysis, stating how "many conditions including schizophrenia, schizoaffective disorder, bipolar affective disorder, personality disorder, learning disability, substance misuse disorder, and functional and somatic illnesses impairing an individual's capacity to accurately self-report."
For the analysis, the researchers looked at data from over 1,200,000 U.S. adults who participated in the one of the CDC Behavioral Risk Factors Surveillance System survey between 2011 and 2015. Exercise behaviors, "bad" mental health days, and medical histories (including psychiatric diagnoses) were self-reported by participants.
In an exploratory, post-hoc analysis, Chekroud's group found that people who engaged in mindful exercises -- such as yoga and tai chi -- saw an even greater reduction in mental health burden.
Even small activity, such as engaging in household chores, was tied to a 9.7% drop in poor mental heath days per month equating to around a half a day less, compared with those who didn't exercise at all.
Type of exercise wasn't the only factor associated with improved mental health -- so did frequency and duration of weekly exercise. Specifically, people who exercised for 45 minutes, three to five times per week saw larger improvements in their mental health. However, exercise frequency had a U-shaped association with decreased mental health burden, so those who exercised between three to four times per week saw the greatest reduction in mental health burden, even compared with those who exercised five or more times per week, also apparent across all types of exercise.
"In units commonly used in public health guidelines, people exercising between 120 min and 360 min per week had the lowest mental health burden," the group stated.
All people experienced this mental health improvement tied to exercise, with apparent benefits seen across all age groups, racial groups, all levels of incomes, and for men and women.
The authors noted some study limitations including the fact that its cross-section design could not establish causality. However, they suggested that "inactivity might be both a symptom of and contributor to poor mental health, whereas activity might be an indicator of and contributor to resilience.""