A new study has found that both moderate and vigorous physical activities are associated with lower levels of specific depressive symptoms, notably anhedonia (loss of interest or pleasure) and fatigue. But physical activity appears to be unrelated to other depressive symptoms, such as suicidal ideation, difficulty concentrating, and sleeping problems.
The findings, published in the Journal of Affective Disorders, provide important insights into the relationship between depression and exercise. The research also highlights the importance of examining the distinct aspects of depression.
Depression, a widespread mental health issue, has traditionally been treated with antidepressants and psychotherapy. However, these methods have not significantly reduced the prevalence of depression at a population level. This gap in treatment efficacy, combined with issues such as delayed access to therapy and limited long-term success, prompted researchers to explore additional, easily accessible treatment options. Physical activity, a modifiable health behavior, emerged as a potential candidate due to its known benefits in alleviating depressive symptoms in both clinical and subclinical settings.
“Physical activity is a promising target for behavioral interventions to alleviate depression as it is accessible and implementable at population level,” said study author Eetu Soini, a doctoral researcher at University of Helsinki. “However, how physical activity and depression are related is poorly understood, though there are different hypotheses floating around.”
“Intuitively, physical activity could affect depression via biological (e.g. inflammation), psychological (e.g. self-esteem) or social (e.g. social aspects related to physical activity) mechanisms or a combination of these. We were interested in whether the association is symptom-specific which could provide some evidence what the possible mechanism(s) could be.”
The study utilized data from the U.S. National Health and Nutrition Examination Surveys, which annually samples approximately 5,000 individuals to represent the non-institutionalized U.S. population. In total, the study encompassed data from 28,520 participants, providing a robust sample for analysis.
Depressive symptoms were assessed using the Patient Health Questionnaire 9, a tool aligning with major depressive disorder criteria in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). It evaluates the frequency of nine depressive symptoms over a two-week period.
These nine depressive symptoms include: “Little interest or pleasure in doing things,” “Feeling down, depressed, or hopeless,” “Trouble falling or staying asleep, or sleeping too much,” “Feeling tired or having little energy,” “Poor appetite or overeating,” “Feeling bad about yourself or that you are a failure or have let yourself or your family down,” “Trouble concentrating on things, such as reading the newspaper or watching television,” “Moving or speaking so slowly that other people could have noticed. Or the opposite being so fidgety or restless that you have been moving around a lot more than usual,” and “Thoughts that you would be better off dead, or of hurting yourself.”
Physical activity levels were self-reported and categorized into three types: moderate-intensity (like brisk walking), vigorous-intensity (like running), and activity related to daily transportation (like walking or biking to work or stores). The study also accounted for various covariates like age, sex, race, education, body mass index, smoking status, alcohol use, number of chronic diseases, and functional limitations.
The researchers discovered that moderate-intensity physical activity was associated with lower depressive symptom sum scores, particularly for those engaging in 1-2 hours per week. This activity also showed a dose-response association with certain symptoms like loss of interest/pleasure and fatigue, meaning that greater amounts of physical activity correlated with fewer symptoms.
Similarly, vigorous-intensity physical activity demonstrated associations with reduced fatigue and appetite symptoms. However, the dose-response pattern for the symptom of “loss of interest/pleasure” was less clear compared to moderate-intensity activity.
Intriguingly, walking or biking as a means of transport did not show a consistent association with depressive symptom sum scores but was linked with reduced fatigue in a dose-response manner. This suggests that even lower-intensity physical activities might have specific benefits.
The findings suggest that “even smaller amount of physical activity can be sufficient for alleviating mood,” Soini told PsyPost.
The study also highlights that the benefits of physical activity on depressive symptoms are not uniform. While some symptoms like anhedonia and fatigue showed a clear association with physical activity, other symptoms did not exhibit the same level of association.
“Our results suggest that physical activity may not affect all the depressive symptoms equally,” Soini explained. “The symptoms affected in our study were ‘loss of interest/pleasure’ and ‘fatigue.’ We hypothesised that behavioural activation could explain the observed results. Engaging in activities that promote better mood could further facilitate these behaviors and improve well-being.”
To ensure the robustness of their findings, the researchers also analyzed data specifically from participants with higher depressive scores and considered the effects of psychopharmacological treatments. The findings remained consistent. But, like all research, the study includes some caveats.
“The study was cross-sectional, and thus the observed results could be explained by reverse causality, that is people who are more fatigued and have low mood may be more inactive,” Soini explained. “And there may be unobserved factors that could affect both physical activity and depression, and thus the association observed may not be causal. Lastly, depression was measured with PHQ-9 which corresponds to DSM-5 criteria, but different depression scales include different set of symptoms. Replication with other depression scales could be beneficial for the field.”
Future research could address these limitations by using longitudinal designs, which track changes over time, and incorporating objective measures of physical activity, like wearable fitness trackers. Additionally, exploring the biological and psychological mechanisms behind the observed associations could offer deeper insights.
“Having my background in psychology, I think more nuanced view on depression is warranted,” Soini added. “Currently depression is assessed using sum scores, in which different symptoms ranging from affective to somatic, are reduced to a single score reflecting the severity of depression. The same sum score can be achieved by different combinations of symptoms, resulting in heterogeneous diagnosis. For anyone interested in the topic, I would recommend reading Eiko Fried’s article ‘Problematic assumptions have slowed down depression research: why symptoms, not syndromes are the way forward,‘ a personal favorite of mine.”
The study, “Physical activity and specific symptoms of depression: A pooled analysis of six cohort studies“, was authored by Eetu Soini, Tom Rosenström, Ilmari Määttänen, and Markus Jokela.
