By the numbers

220,361

Number of students who took the Advanced Placement Psychology exam in 2012, up 11 percent from 2011 and more than 400 percent from 2002, according to the College Board.

4x

The increase in the number of emergency-room visits by young adults due to Ritalin, Adderall and other attention-deficit hyperactivity disorder drugs between 2005 and 2011, according to a 2013 report from the Substance Abuse and Mental Health Services Administration.

3/5

Fraction of Americans with a depression diagnosis who do not meet the DSM criteria for a major depressive episode, according to an April study in Psychotherapy and Psychosomatics that included 5,639 people ages 12 and older. Only 14.3 percent of those 65 or older met the criteria.