The Substance Abuse and Mental Health Services Administration's National Survey on Drug Use and Health showed 11.4 million adults -- 5 percent of the adult population -- suffered from serious mental illness in the past year. Serious mental illness is defined as one that resulted in serious functional impairment, which substantially interfered with or limited one or more major life activities.
The rate of mental illness was 30 percent in those ages 18-25, and 14.3 percent in those ages 50 and older, the report said.
Adult women were more likely than men to have experienced mental illness in the past year -- 23 percent vs. 16.8 percent.
"Mental illnesses can be managed successfully, and people do recover," Pamela S. Hyde, administrator of SAMHSA, said in a statement. "Mental illness is not an isolated public health problem. Cardiovascular disease, diabetes and obesity often co-exist with mental illness and treatment of the mental illness can reduce the effects of these disorders."
The World Health Organization calculated mental illness accounted for more disability than any other group of illnesses, including cancer and heart disease, in developed countries.