"A simple, free way to boost mental health is to exercise outdoors, whether walking, gardening or cycling, concludes a recent study on "green" exercise.

"Every green environment improved both self-esteem and mood," even urban parks, says the study by Jo Barton and Jules Pretty of the United Kingdom's University of Essex. Places with water gave an extra lift."

More at:

http://content.usatoday.com/co...uts-green-exercise/1

Also see:

http://pubs.acs.org/doi/full/10.1021/es101129n

http://pubs.acs.org/doi/abs/10.1021/es903183r