Mental health problems affect more Mexican-Americans and non-Hispanic whites born in the U.S. than new immigrants from the same countries, says the National Institutes of Health (NIH).

The news comes from a study conducted by the National Institute on Alcohol Abuse (search) and Alcoholism (NIAAA), a branch of the NIH. It appears in the December issue of the Archives of General Psychiatry.

America has long been considered a “melting pot” of different nationalities and ethnicities. But effects of immigration aren’t always detailed in research. For instance, past mental health studies often grouped all Mexican-Americans together, without distinguishing between newcomers and those born in the U.S.

That’s starting to change as America’s Hispanic population grows. “In 2003, Hispanics residing in the U.S. became the largest ethnic minority group in the country,” write the researchers, who included NIAAA’s Bridget Grant, PhD.

More than 4,500 Mexican-Americans participated in the mental health survey. Roughly equal numbers were born in the U.S. and Mexico. Nearly 60 percent of the U.S. Hispanic population is of Mexican descent. The survey also included more than 24,000 non-Hispanic white participants, 6 percent of whom were born overseas.

With few exceptions, mental health was worse among U.S.-born participants. They were more likely to have problems including depression, anxiety disorders, and drug or alcohol abuse than new immigrants.

For instance, alcohol, mood, and anxiety disorders were nearly twice as common among U.S.-born Mexican-Americans and non-Hispanic whites. Drug problems affected eight times as many Mexican-Americans born in the U.S. as those from Mexico.

Overall, mental health problems affected almost 48 percent of U.S-born Mexican-Americans and 52 percent of U.S.-born non-Hispanic whites during their lifetime. Only 29 percent of foreign-born Mexican-Americans were affected by a mental illness. Thirty-two percent of foreign-born non-Hispanic whites were affected by mental illness at sometime in their life.

Why the mental health gap? The researchers aren’t exactly sure. New immigrants have the stress of adapting to a new culture. If they can’t make ends meet, the transition can be even harder. But traditionally close-knit Mexican families may offer vital support not seen in other cultures.

That might explain why U.S.-born Mexican-Americans had better mental health than the study’s U.S.-born non-Hispanic whites. But it’s too early to be certain. Additional research is needed to pinpoint the factors that help and hurt mental health for native- and foreign-born Americans.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Grant, B. Archives of General Psychiatry, December 2004; vol 61: pp 1226-1233. News release, NIH/National Institute on Alcohol Abuse and Alcoholism.