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Testing causality in the association between regular exercise and symptoms of anxiety and depression.

Abstract

CONTEXT
In the population at large, regular exercise is associated with reduced anxious and depressive symptoms. Results of experimental studies in clinical populations suggest a causal effect of exercise on anxiety and depression, but it is unclear whether such a causal effect also drives the population association. We cannot exclude the major contribution of a third underlying factor influencing exercise behavior and symptoms of anxiety and depression.
OBJECTIVE
To test causal effects of exercise on anxious and depressive symptoms in a population-based sample.
DESIGN
Population-based longitudinal study (1991-2002) in a genetically informative sample of twin families.
SETTING
Causal effects of exercise were tested by bivariate genetic modeling of the association between exercise and symptoms of anxiety and depression, correlation of intrapair differences in these traits among genetically identical twins, and longitudinal modeling of changes in exercise behavior and anxious and depressive symptoms.
PARTICIPANTS
A total of 5952 twins from the Netherlands Twin Register, 1357 additional siblings, and 1249 parents. All participants were aged 18 to 50 years.
MAIN OUTCOME MEASUREMENTS
Survey data about leisure-time exercise (metabolic equivalent task hours per week based on type, frequency, and duration of exercise) and 4 scales of anxious and depressive symptoms (depression, anxiety, somatic anxiety, and neuroticism, plus a composite score).
RESULTS
Cross-sectional and longitudinal associations were small and were best explained by common genetic factors with opposite effects on exercise behavior and symptoms of anxiety and depression. In genetically identical twin pairs, the twin who exercised more did not display fewer anxious and depressive symptoms than the co-twin who exercised less. Longitudinal analyses showed that increases in exercise participation did not predict decreases in anxious and depressive symptoms.
CONCLUSION
Regular exercise is associated with reduced anxious and depressive symptoms in the population at large, but the association is not because of causal effects of exercise.

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  • Publisher Full Text
  • Authors

    De Moor MH, Boomsma DI, Stubbe JH, Willemsen G, de Geus EJ

    Source

    Archives of general psychiatry 65:8 2008 Aug pg 897-905

    MeSH

    Adult
    Anxiety Disorders
    Causality
    Cross-Sectional Studies
    Depressive Disorder
    Diagnostic and Statistical Manual of Mental Disorders
    Diseases in Twins
    Exercise
    Female
    Humans
    Leisure Activities
    Longitudinal Studies
    Male
    Middle Aged
    Netherlands
    Personality Inventory
    Twins, Dizygotic
    Twins, Monozygotic

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't
    Twin Study

    Language

    eng

    PubMed ID

    18678794