A meta-analysis from the Rotman Research Institute at Baycrest Health Sciences in Toronto says that volunteering increases both physical and mental health and those who reap the health benefits of volunteer work log at least 100 hours per year or 2-3 hours per week.

Led by Dr. Nicole Anderson, a senior scientist with Baycrest's Rotman Research Institute and associate professor, University of Toronto, the research team analyzed 73 studies that measured psychosocial, physical or cognitive outcomes of formal volunteer work in adults of a minimum age of 50.

Overall, researchers found that volunteering is associated with reductions in symptoms of depression, better overall health and increased longevity, although researchers found that exceeding 100 hours of annual volunteer work did not enhance these benefits.

They found that those who benefitted the most were seniors with health conditions, or other such vulnerabilities, for the feeling of being appreciated or needed is important in the relationship between volunteering and psychological health.

"Taken together, these results suggest that volunteering is associated with health improvements and increased physical activity -- changes that one would expect to offer protection against a variety of health conditions," said Dr. Anderson.

The research team found evidence that volunteering can reduce hypertension and they counted fewer hip fractures among seniors who do a moderate amount of volunteer work.

They were surprised to find few studies investigating the cognitive benefits of volunteer work in seniors and reported not finding even one examining the association between volunteering and the risk of dementia.

More research is necessary, they say, to examine volunteering's potential ability to ward off the many health conditions that put seniors at higher risk for dementia, such as diabetes and stroke.

The study was published in the journal Psychological Bulletin.