Genes can influence vulnerability to depression, but genetic risk is not destiny. A new large-scale study suggests that everyday physical activity may matter not only for whether major depressive disorder occurs, but also for how strongly inherited vulnerability is expressed in depressive symptoms.
Researchers analysing 23,517 adults in the United States combined whole-genome sequencing with long-term Fitbit measurements and depression information from the All of Us Research Program. Participants had worn their devices for an average of 582 days, giving the researchers an unusually detailed view of physical activity over time rather than relying on a single questionnaire about exercise habits.
The central finding was nuanced. Higher genetic risk and lower physical activity were each associated with major depressive disorder, but physical activity did not significantly change the relationship between genetic risk and whether someone had an MDD diagnosis. When the researchers examined depressive symptom severity instead, however, a different pattern emerged: higher physical activity consistently weakened the association between polygenic risk and symptom burden.
Why this distinction matters
Depression is often treated as a binary outcome in large datasets: a person either meets a diagnostic definition or does not. Yet depression also varies substantially in severity. Two people with the same diagnosis can experience very different levels of distress and impairment, while symptoms can change over time.
The new research, published in Nature Mental Health on 2 October 2026, addresses both dimensions. That is important because gene and environment interactions may be easier to detect in a continuous measure of symptoms than in a yes-or-no diagnostic category. The findings therefore do not show that exercise cancels inherited susceptibility to depression. Instead, they suggest that behaviour may be related to how genetic vulnerability is expressed once symptom burden is considered.
More than 23,000 genomes paired with long-term wearable data
The researchers studied 23,517 All of Us participants who had both whole-genome sequencing data and usable long-term Fitbit records. The average participant was about 56 years old, the age range extended from 18 to 92, and 67.2% of the sample was female.
Physical activity was measured in two practical ways: daily step counts and minutes of moderate-to-vigorous physical activity. The mean wearable observation period was 582 days. This extended measurement period is a major strength because physical activity varies from day to day and short monitoring windows can misrepresent a person’s usual behaviour.
Genetic vulnerability was represented using polygenic risk scores. These scores combine information across many genetic variants associated with a trait, producing an estimate of relative inherited susceptibility rather than identifying a single depression gene. Major depressive disorder was defined using information from both electronic health records and self-reported lifetime diagnosis.
The team then used regression models to test the separate effects of genetic risk and physical activity, as well as whether the two interacted. Models accounted for demographic covariates, and the researchers tested multiple ways of defining physical activity and depressive symptom severity to determine whether the main pattern depended on one particular analytical choice.
Activity and genetic risk independently tracked depression diagnosis
For major depressive disorder diagnosis, the results followed an intuitive pattern. Higher polygenic risk was robustly associated with a greater likelihood of MDD, while higher physical activity was associated with lower risk across the activity measures examined.
What the researchers did not find is equally important. There was no statistically significant interaction between polygenic risk and physical activity for MDD onset. In other words, the data did not support the claim that being more physically active neutralised the genetic association with receiving an MDD diagnosis.
This prevents an overly simple interpretation of exercise as a genetic shield. Both genetic liability and behaviour were relevant, but for the binary diagnostic outcome their associations were largely independent.
A different pattern emerged for symptom severity
When depressive symptoms were analysed as a matter of degree, the picture changed. Genetic risk and physical activity again showed significant main effects, but the researchers also found consistent negative interactions between the two.
Higher physical activity was associated with a weaker relationship between polygenic risk and depressive symptom burden. Crucially, this pattern appeared across the different physical activity operationalisations and alternative definitions of symptom severity used by the researchers. It also remained evident across different model specifications.
That consistency strengthens the finding, although it does not establish that increasing activity will directly reduce the effect of genetic risk. The study is observational, so the direction of influence cannot be settled from these data alone. Depression itself can reduce motivation, energy and activity, creating the possibility of reverse causation. Other health, socioeconomic and behavioural factors may also contribute to the observed relationships.
Wearables add something important to depression research
One of the study’s most useful methodological contributions is its use of long-term device measurements. Exercise and depression research frequently depends on self-reported activity, which can be affected by recall errors and differences in how people interpret terms such as moderate exercise.
Consumer wearables are not laboratory instruments and their estimates also contain measurement error, but repeated observations over hundreds of days can capture habitual movement at a scale that would be difficult to obtain through traditional research assessments. Combining these records with genomic information makes it possible to ask more precise questions about how behavioural and inherited factors relate to one another.
The result is especially relevant to the emerging field of precision mental health. Genetic information may help researchers identify differences in vulnerability, while modifiable behaviours provide potential intervention targets. This study suggests that symptom severity could be a particularly informative outcome when researchers investigate those interactions.
What the study does not prove
The findings should not be interpreted as a prescription for people with depression to simply exercise more. Major depressive disorder is a complex condition, and treatment can include psychological therapy, medication, social support, lifestyle interventions and other forms of care depending on the individual.
The analysis also involved people who elected to participate in the All of Us programme and had compatible long-term Fitbit data, which may differ systematically from the wider population. The sample was 67.2% female and had a mean age of about 56, so the magnitude of associations may not transfer unchanged to every demographic group. Polygenic scores can also differ in predictive performance across ancestry groups, an important consideration for any attempt to translate genetic risk estimates into practice.
Finally, an interaction in an observational statistical model is not evidence that physical activity biologically overrides genetic risk. Randomised and longitudinal intervention research would be needed to test whether deliberately increasing activity changes depressive symptom trajectories differently across levels of genetic susceptibility.
The broader implication
The most informative message is therefore not that genes matter less than behaviour, or vice versa. The study shows why researchers may need to examine both at the same time and why the outcome being measured matters.
For the presence of an MDD diagnosis, genetic vulnerability and physical activity appeared to contribute largely independently. For the severity of depressive symptoms, the relationship was more interactive, with higher activity associated with a weaker link between polygenic risk and symptom burden.
If future studies establish a causal effect, the finding could strengthen the case for incorporating objectively measured physical activity into personalised approaches to depression prevention and management. For now, it offers a substantial new piece of evidence that inherited vulnerability and everyday behaviour can relate differently depending on whether researchers ask who develops depression or how severely symptoms are expressed.
Source Information
Study: He, Q., Zhang, J., Beevers, C.G. et al. “Associations and interactions between genetic vulnerability and physical activity with MDD in the All of Us Research Program.” Nature Mental Health (2026).
Published: 2 October 2026
DOI: 10.1038/s44220-026-00738-x
