Exercise has long been found to have a positive effect upon mental health. This article [here] attempts to pinpoint the most helpful amount and types of exercise in this regard. It states that exercising around 30-60 minutes between three and five times a week is most helpful. Exercising for more than 23 times a month or for longer than 90 minute sessions is associated with poorer mental health outcomes. Within these limits, all forms of exercise are helpful but team sports, cycling, aerobics and going to the gym appear to be the best.