A new government report finds 42.5 million American adults, or 18.2 percent of the adult population, suffers from some form of mental illness.
About 4 percent suffers serious mental illness that impedes day-to-day activities.
The findings come from the Substance Abuse and Mental Health Services Administration (SAMHSA), Newsweek reports.
The state with the lowest rate of overall and severe mental illness was New Jersey, the report found.
The overall mental illness rate in the state was 14.7 percent, while the rate of severe mental illness was 3.1 percent. In Utah, the state with the highest rate of overall mental illness, 22.3 percent of adults experienced mental illness. West Virginia had the highest rate of severe mental illness, at 5.5 percent.
The researchers conclude, "factors that potentially contribute to the variation are not well understood and need further study."
"This report shows that, while the percentages vary, people in every state experience mental illness," SAMHSA Administrator Pamela S. Hyde said in a news release. "The findings from this report will help state and local public health officials and others address the mental health needs of the people in their communities."