ABSTRACT
Worldwide, over 340 million people are impacted by depression.1 In the United States alone, 16% of the population will experience major depression at some point in their lifetime. In fact, depression is considered a leading cause of disability and is likely to be at least the second leading contributor to worldwide disease burden by 2020.2 It also appears that depression is linked to increased functional disability and further exacerbates functional disability in individuals suffering from chronic diseases.3 Likewise, anxiety disorders afict more than 30 million people in the United States and cost an estimated $42 billion/year. Overall, depression and anxiety are the two most commonly reported mental health disorders.1,4 To make matters worse, it appears that at least one-third to two-thirds of depressed patients will not experience successful alleviation of symptoms with the rst antidepressant therapy prescribed, with as many as 30% being classied as non-responders, that is, not responding to even multiple interventions.5 Perhaps the more concerning fact is that antidepressants and anxiolytic drugs are both expensive and accompanied by a number of serious side effects. Fortunately, evidence suggests that a viable alternative low-cost alternative therapy, or at least an important adjunct, exists that has positive outcomes and is free from the negative side effects: exercise.
