It has been known for a while now that even moderate exercise may be beneficial for depressive mood (besides being a good thing to do for a generally healthy lifestyle), although there are also conflicting findings (Cooney et al., 2013).

Likewise, low mood and other symptoms of depression can lead to reduced energy levels and a whole host of other unpleasant things that can be expected to reduce the “desire” to get up and active (Roshanaei-Moghaddam et al, 2009).

It’s a subject we’ve covered many times in previous Mental Elf blogs about exercise for depression.

Overall, the link between physical activity and depression could be directional, although no-one has looked at this hypothesis conclusively. A recent prospective cohort study published in JAMA Psychiatry provides some interesting insights (Pinto Pereia et al, 2014).

Methods

The authors examined the link between symptoms of depression and physical activity during the “hotspot” years of depression (i.e. from age 23 to 50). To that end, they analysed data from the 1958 British Birth Cohort that included all persons born in Great Britain in a specific week in March 1958 who were followed up to their 50th birthday in 2008.

Detailed information regarding depressive symptoms and physical activity at several ages (23, 33, 42 or 50 years) was available for 11,000 people.

Odd’s ratios (OR) and 95% confidence intervals (CI) were calculated.

Body mass index, likely an important mediator of the association between physical activity and depression, and several other variables were controlled for.

Results

• At most ages (except for age 33 years) and across both sexes, there was a trend towards lower depressive symptoms with increased physical activity
• Over all ages, there were fewer depressive symptoms in those who exercised compared to those who did not
  • For instance, activity once a week was associated with a 7% lower OR for depression (OR 0.93, CI 0.91 to 0.95)
• Notably, people in any age group who made the switch from inactive to active 3 times per week, saw their OR for depression drop by 19% five years later (OR 0.81, CI 0.76 to 0.87)
• Likewise, an increase in depressive symptoms was associated with reduced weekly exercise frequency
• This relationship between depressive symptoms and activity decreased with age, so that there were no differences in activity at age 43

Summary

The authors concluded that:

the relationship between activity and depressive symptoms was bidirectional, albeit more persistent during adult life in the direction from activity to depressive symptoms.

Limitations

• The study relies on questionnaire data on physical activity that provided no information on how intensely and for how long participants had exercised (besides being based on recall, which comes with flaws of its own)
• In addition, the study was observational, which means that in theory some uncontrolled covariates could have influenced the outcome
• Also, sample attrition could have introduced a bias, as for instance people with the highest levels of depression (or lowest levels of physical activity) could have been selectively lost, which would have underestimated the link between depression and exercise
• However, the authors rightly comment that they tried to mitigate for these limitations with the statistical processes they employed and the study design they selected; using multilevel regression models and including participants with at least one response.

Conclusion

This is a very relevant study to the field of depression as it indicates that exercise is a viable therapy for depression at any age (besides being a healthy choice in general).

It also shows that being depressed when younger may lead to inactivity, which further exacerbates depression and vice versa. This vicious circle is where stepping up the physical activity may help: Exercise is a therapy that can be easily “self-administered”, does not require any prescription and may be prophylactic. For example, this study found that increasing activity levels from nothing to at least three times a week reduced the odds of becoming depressed by nearly 20%.

This evidence adds further weight to the case for exercise as a treatment option for people with mild depression.

Link

Pinto Pereira, S. M., Geoffroy, M.-C., & Power, C. (2014). Depressive Symptoms and Physical Activity During 3 Decades in Adult Life. Bidirectional Associations in a Prospective Cohort Study. JAMA Psychiatry. doi: 10.1001/jamapsychiatry.2014.1240 [PubMed abstract]

Other references

Cooney GM, Dwan K, Greig CA, Lawlor DA, Rimer J, Waugh FR, McMurdo M, Mead GE. Exercise for depression. Cochrane Database of Systematic Reviews 2013, Issue 9. Art. No.: CD004366. DOI: 10.1002/14651858.CD004366.pub6.

Roshanaei-Moghaddam, B., Katon, W. J., & Russo, J. (2009). The longitudinal effects of depression on physical activity. General Hospital Psychiatry, 31(4), 306–15. doi:10.1016/j.genhosppsych.2009.04.002 [PubMed abstract]

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