According to the results of a National Institutes of Health (NIH) study, reported in the December issue of the Archives of General Psychiatry (Volume 61), Mexican Americans and non-Hispanic Whites* born in the United States have a higher risk for developing psychiatric disorders than their foreign-born counterparts who have immigrated to the United States. The psychiatric disorders included alcohol and drug use disorders, major depression, dysthymia, mania, hypomania, panic disorder, social and specific phobia, and general anxiety disorder.

Based on the 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), the analysis is the first to consider immigration status in conjunction with psychiatric morbidity in each of four comparison groups: U.S.-born Mexican Americans, Mexican immigrants to the United States, U.S.-born non-Hispanic Whites, and non-Hispanic White* immigrants to the United States. Earlier studies compared psychiatric disorder rates among U.S.- and foreign-born Mexican Americans to either rates for U.S.-born non-Hispanic Whites or rates for the entire U.S. population, thereby confounding immigration status and ethnicity.

"The remarkable pattern seen in these results defies explanation based on current knowledge," according to George Kunos, M.D., Ph.D., Scientific Director, Division of Intramural Biological and Clinical Research at the National Institute on Alcohol Abuse and Alcoholism (NIAAA), the NIH institute that conducted the study. "Additional careful research is required to fully understand the influences of individual and environmental factors in the causes of psychiatric disorders."

"As often occurs, our epidemiologists — researchers who study conditions and behaviors across large population groups — pose new and intriguing questions for researchers in other disciplines," he said. "Although it may be some time before scientists fully understand the causes of these disorders, service providers and policy makers have immediate use for the results."

Lead author Bridget Grant, Ph.D., Chief of the Laboratory of Biometry and Epidemiology in NIAAA's intramural research program, and her colleagues found that non-Hispanic Whites' lifetime rate of experiencing a psychiatric disorder (51.2 percent) was far greater overall than that for all Mexican Americans (36.7 percent). Psychiatric disorders were more prevalent among U.S.-born survey participants (47.6 percent among Mexican Americans and 52.5 percent among non-Hispanic Whites) than among their foreign-born counterparts (28.5 percent and 32.3 percent, respectively). Lifetime rates of alcohol use disorder and specific mood and anxiety disorder among U.S.-born Mexican Americans and non-Hispanic Whites were nearly twice those of their foreign-born counterparts. Drug use disorder rates among U.S.-born non-Hispanic Whites were more than twice those of their foreign-born counterparts, whereas the corresponding rates among U.S.-born Mexican Americans (12 percent) were eight times those of Mexican Americans born outside the United States (1.7 percent).

After controlling for age, sex, marital status, place of residence, geographic region, education, and family income, the authors examined relationships among the four comparison groups and each psychiatric disorder. They determined that, with few exceptions, risk for all the psychiatric disorders assessed was significantly greater among U.S.-born than foreign-born non-Hispanic Whites and among U.S.-born than foreign-born Mexican Americans.

"Foreign-born study participants were at lower risk of major psychiatric disorders even though they may have experienced greater stress due to low socioeconomic status or adapting to a new culture," noted Dr. Grant. "This is consistent with the 'healthy migrant' model that predicts that foreign-born persons in good health are more likely than those in poor health to immigrate to the United States. However, this hypothesis does not explain the study's finding that risk for drug dependence and specific mood and anxiety disorders was similar among foreign-born non-Hispanic Whites and U.S.-born Mexican Americans." Also weighing against the healthy migrant model, the authors report, is the fact that psychiatric disorder rates among foreign-born Mexican American immigrants are similar to but not lower than rates in Mexico City.

The study findings suggest that acculturation has negative effects on the mental health of both Mexican Americans and non-Hispanic Whites and that cultural retention (i.e., the preservation of traditional family networks and customs) has protective effects on the mental health of Mexican Americans, according to the authors: "While foreign-born Mexican Americans and non-Hispanic Whites did not differ in the risk of psychiatric disorders, U.S.-born Mexican Americans had a clear advantage over U.S.-born non-Hispanic Whites."

Identifying the specific components of various cultures that may reduce possible negative effects of acculturation on mental health or protect against psychopathology holds great promise in helping to guide future prevention and treatment efforts, the authors conclude.

The NESARC is a representative survey of the U.S. civilian noninstitutionalized population aged 18 years and older. With more than 43,000 adult Americans participating, the NESARC is the largest study ever conducted of the co-occurrence of alcohol and drug use disorders and other psychiatric disorders as defined by the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) among U.S. adults. Earlier NESARC reports (see 2004 News Releases at www.niaaa.nih.gov) estimate the prevalence of alcohol and drug use disorders, mood and anxiety disorders, personality disorders, and the co-occurrence of alcohol use disorders with other psychiatric conditions.

For an interview with Dr. Grant, please contact the NIAAA Press Office at (301) 443-0595 or (301) 443-3860. For a copy of the study, media representatives may contact the NIAAA Press Office or mediarelations@jama-archives.org. Full text will be accessible to the public at 3:00 PM CT on December 6 at www.archgenpsychiatry.com.

The National Institute on Alcohol Abuse and Alcoholism, a component of the National Institutes of Health, U.S. Department of Health and Human Services, conducts and supports approximately 90 percent of the U.S. research on the causes, consequences, prevention, and treatment of alcohol abuse, alcoholism, and alcohol problems and disseminates research findings to science, practitioner, policy making, and general audiences. Additional alcohol research information is available at www.niaaa.nih.gov. Additional information on drug abuse and dependence is available from the National Institute on Drug Abuse at www.nida.nih.gov. Additional information on other psychiatric disorders is available from the National Institute of Mental Health at www.nimh.nih.gov.