Exercise doesn't seem to ease anxiety or depression, says a recent study conducted in the Netherlands among twins, one of whom exercised, while the other didn't.
Marleen HM De Moor of VU University Amsterdam and colleagues studied 5,952 twins from the Netherlands Twin Register, along with 1,357 additional siblings and 1,249 parents.
Participants, aged between 18 and 50, filled out surveys about leisure-time exercise and completed four scales measuring anxious and depressive symptoms.
Associations observed between exercise and anxious and depressive symptoms "were small and were best explained by common genetic factors with opposite effects on exercise behaviour and symptoms of anxiety and depression," the authors note.
"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."
Exercise behaviour in one identical twin predicted anxious and depressive symptoms in the other, meaning that if one twin exercised more, the other tended to have fewer symptoms.
However, the same was not true of dizygotic (fraternal) twins or other siblings, who share only part of their genetic material.
In addition, analyses over time showed that individuals who increased their level of exercise did not experience a decrease in anxious and depressive symptoms.
The results do not mean that exercise cannot benefit those with anxiety or depression, the authors noted, only that additional trials would be needed to justify this type of therapy.
These findings were reported in the August issue of Archives of General Psychiatry.