Harvard psychiatrist John Ratey wrote a book Spark: The Revolutionary New Science of Exercise and the Brain (http://www.amazon.com/Spark-Revolutionary-Science-E

Harvard psychiatrist John Ratey wrote a book Spark: The Revolutionary New Science of Exercise and the Brain (http://www.amazon.com/Spark-Revolutionary-Science-Exercise-Brain/dp/0316113506 http://www.amazon.com/Spark-Revolutionary-Science-Exercise-B...) where he explains how aerobic exercise (esp high-intensity interval training/sprints) stimulates neurogenesis and balances the neurotransmitters in the brain. He shows exercise can be more effective than drugs for the treatment of anxiety, stress, depression, and ADHD.