One in five Americans aged 18 or older experienced mental illness in the past year, according to a 2012 report from the Substance Abuse and Mental Health Services Administration. The report, available at www.samhsa. gov, notes that mental illness affected nearly 30% of those aged 18 to 25, compared with less than 15% for those aged 50 and older.

Source: Substance Abuse and Mental Health Services Administration.