A recent study led by a dedicated team of ISEH and UCL researchers, John Vincent, Snehal M. Pinto Pereira, Jane Maddock, Dylan M. Williams, Mark Hamer, Jonathan P. Roiser, and Amy E. Taylor and published in Journal of Affective Disorders, suggests that muscle strength, especially in women, may directly reduce the risk of depression and its symptoms.
The researchers found no evidence that aerobic fitness affects depression, but their results indicate that increasing muscle strength could help both prevent and treat the condition. This highlights strength training as a potentially effective and targeted approach to improving mental health.
Although physical activity is widely known to protect against depression, the biological mechanisms behind this link are still not fully understood. To explore this, the authors focused on two possible pathways:
- Cardiorespiratory fitness (the ability of the heart and lungs to supply oxygen during exercise)
- Muscle strength
Previous research has associated both with lower depression rates, but it has been difficult to establish cause and effect.
Traditional observational studies cannot easily determine causality, as other lifestyle factors may influence results. It is also possible that depression leads to reduced physical activity, rather than poor fitness causing depression.
Method:
To address this, the authors analysed data from 341,326 adults aged 37 to 73 from the UK Biobank. They used Mendelian randomisation, a method that examines genetic variations linked to physical traits. Because these variations are randomly assigned at birth, they act like a natural experiment and help establish cause and effect relationships.
The study examined genetic markers linked to cardiorespiratory fitness and grip strength, the latter being used as an indicator of overall muscle strength (adjusted for body weight). Depression outcomes were measured using self-reports, hospital records, and a detailed questionnaire assessing nine specific symptoms, including low mood, loss of pleasure (anhedonia), appetite changes, fatigue, and concentration difficulties.
Results:
- The findings showed no connection between cardiorespiratory fitness and depression
- Stronger grip strength was clearly associated with a lower risk of depression
- Specifically, a 0.1 kg increase in grip strength per kg of body weight was linked to a 14% lower likelihood of overall depression.
Greater strength was also tied to reduced risk of several symptoms. For example, it was associated with a 21% lower likelihood of experiencing anhedonia and a 44% lower likelihood of appetite changes. It also showed links to reduced depressed mood, fatigue, slowed movement, and concentration problems.
The researchers noted that while muscle strength is only one factor among many, improving it could make a meaningful contribution to reducing depression. The results were consistent across multiple analyses, strengthening confidence in the findings.
When examining differences between sexes, the protective effects of muscle strength were generally stronger in women. Reductions in symptoms like low mood, loss of pleasure, and concentration problems were seen in women but not in men. However, the link between strength and appetite changes was observed in both sexes. No clear association was found between muscle strength and sleep issues or suicidal thoughts.
Access the study published in Journal of Affective Disorders.
Read the article featured in PsyPost.
