Depression is the most common mental health condition, with lifetime prevalence in the U.S. of more than 20%.1 Over 300 million people, or 4.4% of the world’s population, are estimated to be affected by depression, which imposes substantial costs on individuals and on society at large. Health expenditures exceeded $90 billion for treatment of depression and anxiety disorders in the U.S. in 2013.2 There also is a substantial personal cost to depression; for example, 60% of people who die by suicide have a diagnosed mood disorder. Indeed, depression and mood disorders have been shown to have genetic overlap with suicidal behavior in several recent studies.3–6
