Twenty percent of American adults age 18 or older—nearly 46 million persons—experienced mental illness in the past year, according to 2010 data from the National Survey on Drug Use and Health (NSDUH).Among young adults, the rate of mental illness was more than twice as high as the rate among older adults—29.9% in the 18-to-25 group, compared with 14.3% in the 50-and-older group.Women were more likely than men to have had a mental illness in the past year (23.0% versus 16.8%). In addition, 11.4 million adults—or 5% of the adult population—had a serious mental illness in the past year.

Rates of past-year mental illness varied by racial-ethnic group. The rate was highest among persons reporting two or more races—25.4%—followed by 20.6% among whites, 19.7% among African Americans, 18.7% among American Indians or Alaska Natives, 18.3% among Hispanics, and 15.8% among Asians. An estimated 8.7 million adults (3.8%) had serious thoughts of suicide in the past year, according to the NSDUH report. The percentage was highest among persons age 18 to 25 (6.6%), followed by those age 26 to 49 (4.1%) and those age 50 and older (2.5%). A total of 2.5 million adults (1.1%) made suicide plans in the past year, and 1.1 million adults (.5%) attempted suicide.

These 2010 prevalence estimates are similar to estimates from previous years and give no indication of dramatic increases or decreases. NSDUH is an annual survey of approximately 67,500 persons in the civilian, noninstitutionalized population age 12 and older conducted by the Substance Abuse and Mental Health Services Administration (SAMHSA). The survey covers residents of households and persons in noninstitutional group quarters (such as shelters, rooming and boarding houses, college dormitories, and halfway houses). Excluded are persons with no fixed household address, active-duty military personnel, and residents of institutional group quarters (such as correctional facilities, nursing homes, and long-term hospitals). Because of its statistical power, it is the nation's premier source of statistical information on the scope and nature of many behavioral health issues. The NSDUH defines mental illness among adults as having had a diagnosable mental, behavioral, or emotional disorder (excluding developmental and substance use disorders) in the past year on the basis of DSM-IV criteria. A serious mental illness is defined as one that results in functional impairment that substantially interferes with or limits one or more major life activities.

Substance use disorders were far more prevalent among adults with past-year mental illness, the NSDUH data show. Adults with any mental illness were more than three times as likely as those with no mental illness to meet criteria for substance dependence or abuse—20.0% compared with 6.1%.Among adults with serious mental illness, the rate of co-occurring substance use disorders was even higher (25.2%). In 2010 young adults (age 18 to 25) had the highest rate of co-occurring disorders (9.6%), followed by adults age 26 to 49 (4.7%) and adults age 50 and older (1.3%).

Rates of co-occurring disorders rose with increasing poverty: 3.2% among adults with a family income at or above 200% of the federal poverty level, 4.7% among those with income between 100% and 199% of the poverty level, and 6.7% among those with an income below 100% of the poverty level. Among adults enrolled in Medicaid in 2010 or whose children were in the Children's Health Insurance Program, 6.7% had co-occurring disorders, similar to the rate among adults without health insurance (6.6%) and higher than the rate among adults with private health insurance (3.0%). The prevalence of co-occurring disorders also rose with unemployment: 3.3% among adults employed full-time, 5.4% among those employed part-time, and 8.2% among unemployed adults. By race-ethnicity, co-occurring disorders were most prevalent among American Indians or Alaska Natives (7.7%). Rates for other groups in 2010 were 1.8% among Asians, 2.3% among Native Hawaiians or other Pacific Islanders, 4.0% among whites, 4.2% among blacks, 4.3% among Hispanics, and 5.8% among persons reporting two or more races.

Among American adults who experienced a mental illness in 2010, about four in ten people (39.2%) received mental health services during that period. The rate of treatment among those with a serious mental illness was notably higher (60.8%).

The complete report, Results From the 2010 National Survey on Drug Use and Health: Mental Health Findings, is available on the SAMHSA Web site at www.samhsa.gov/data/nsduh/2k10mh_findings.