Only about half of people with major depression receive treatment for the disorder and one fifth receive treatment consistent with current practice guidelines, according to a study published in the Archives of General Psychiatry and reported by the National Institutes of Mental Health (NIMH). What’s more, African Americans and Mexican Americans were the least likely to receive treatment.

A number of surveys confirm that people struggling with mental illness often don’t receive the treatment they need. Given that depression is the leading cause of disability in the United States, quantifying how few receive treatment is vital.

The study—conducted by researchers at Wayne State University in Detroit, the University of Michigan in Ann Arbor, the University of California in Los Angeles and the Harvard School of Public Health in Boston—looked at data from the Collaborative Psychiatric Epidemiology Surveys conducted by the NIMH. The analysis included more than 15,000 people 18 years and older.

Researchers found that 51 percent of those who met the criteria for major depression received treatment in the previous year, and only 21 percent received care consistent with the American Psychiatric Association (APA) guidelines.

Though rates of depression were similar between racial and ethnic groups, there were disparities in who received treatment. Fifty-four percent of whites received treatment, compared with 40 percent of African Americans and just 34 percent of Mexican Americans.

Overall, people tended to receive psychotherapy more often than medication. When psychotherapy was provided, it was also more likely to be consistent with APA guidelines than medication that was prescribed. Caribbean blacks, African Americans and Mexican Americans were the most likely to be receiving psychotherapy not consistent with APA guidelines.

While those with health insurance were more likely to receive some sort of care, they were no more likely to receive the standard-of-care according to APA guidelines.