" One study proved just how powerful exercise can be: Three groups of depressed patients were assigned to different coping strategies—one group took antidepressant medication, one group exercised for 45 minutes three times a week, and one group did a combination of both.33 After four months, all three groups experienced similar improvements in happiness. The very fact that exercise proved just as helpful as anti-depressants is remarkable, but the story doesn’t end here. The groups were then tested six months later to assess their relapse rate. Of those who had taken the medication alone, 38 percent had slipped back into depression. Those in the combination group were doing only slightly better, with a 31 percent relapse rate. The biggest shock, though, came from the exercise group: Their relapse rate was only 9 percent! In short, physical activity is not just an incredibly powerful mood lifter, but a long-lasting one. "

― Shawn Achor , The Happiness Advantage: The Seven Principles of Positive Psychology That Fuel Success and Performance at Work