The article below is reposted from PsychologyToday.com and explores the science behind the challenges and benefits of getting the 'right' amount of exercise to get the most from its anti-depressant properties:
Dose Matters: Exercise as Anti-depressant by Dr. Victoria L. Dunckley - a board-certified psychiatrist.
"Interestingly, in a recent study in which patients were assigned to antidepressant medication, exercise, or combined medication plus exercise, the combination treatment did not appear to provide any additional benefit than exercise alone—which was equivalent to the medication effect (sertraline, brand-name Zoloft was used). In fact, when researchers looked at 6-month relapse rates, the exercise-only group did better than the combination group. (only 9% had relapsed compared to 30% in the other two groups.)"
"...based on other research regarding the beneficial of morning bright-light exposure on mood and sleep quality, that an outdoor workout in the morning will augment exercise’s effect even further."