Regular exercise has previously been associated with the reduction of anxiety and depression. This has been concluded through experiments with specific clinical populations, but a causal relationship has not yet been established in the general population. Because there is the possibility of a confounding factor that causes exercise and reduction of symptoms to coincide, it is important to investigate the causal relationship between the two.
To investigate this, Marleen H. M. De Moor, M.Sc., of VU University Amsterdam, the Netherlands, and colleagues performed a twin study with 5,952 twins from the Netherlands Twin Register, 1,357 additional siblings, and 1,249 parents. All participants were between the ages of 18 and 50. They were evaluated through surveys regarding leisure exercise and through several scales to measure symptoms of anxiety and depression.
After analysis, the authors found that the associations that were observed between the symptoms and exercise were "small and were best explained by common genetic factors with opposite effects on exercise behavior and symptoms of anxiety and depression." However, in observing the twins, "the twin who exercised more did not display fewer anxious and depressive symptoms than the co-twin who exercised less."
Notably, higher exercise levels of one twin were associated with lower levels of depressive symptoms in the other twin. This was not displayed in fraternal twins or in other siblings. Ultimately, it was shown that individuals who increased their levels of exercise over time generally did not display lessened anxious or depressive symptoms. All of these points lead to a hypothesis that this association is somehow genetically related. The authors comment: "It is unknown which genes might be involved in voluntary exercise behavior and in the risk for anxiety and depression." They suggest that the genes controlling the neurological pathways processing dopamine, norepinephrine, opioids or serotonin are potential areas for further investigation.
Ultimately, these results indicate that additional trials must be performed before therapy using exercise can be legitimized. This does not mean that exercise cannot benefit these patients. The authors note that "Only voluntary leisure-time exercise is influenced by genetic factors, whereas the other type of exercise [directed and monitored by someone else] is environment-driven. The absence of causal effects of voluntary exercise on symptoms of anxiety and depression does not imply that manipulation of exercise cannot be used to change such symptoms." They indicate that different results may be obtained if this exercise is delivered as a part of a therapy program. They say: "The antidepressant effects of exercise may only occur if the exercise is monitored and part of a therapeutic program."
Testing Causality in the Association Between Regular Exercise and Symptoms of Anxiety and Depression
Marleen H. M. De Moor; Dorret I. Boomsma; Janine H. Stubbe; Gonneke Willemsen; Eco J. C. de Geus
Arch Gen Psychiatry. 2008;65(8):897-905.
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What is Anxiety?For more information on what anxiety is and what to do about it, please see:
What is Anxiety? What Causes Anxiety? What To Do About It.