Study finds environmental factors a primary cause of conduct disorder among Mexican families that migrate to the U.S.
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The prevalence of nonaggressive symptoms of conduct disorder increases dramatically across generations of Mexican-origin populations after migration to the United States, according to a study by an international team of researchers at the UC Davis Health System, RAND Corporation and National Institute of Psychiatry in Mexico City.
The study appears in the December issue of the Archives of General Psychiatry, one of the JAMA/Archives journals.
"Our study shows that there is a large difference in risk for conduct disorder between Mexicans living in Mexico and people of Mexican descent living in the United States," said Sergio Aguilar-Gaxiola, a professor of clinical internal medicine who directs both the UC Davis Center for Reducing Health Disparities and the Community Engagement Program of the UC Davis Clinical and Translational Science Center. "This increase in risk occurring across generations within a migrating population strongly points to the influence of early childhood environmental factors in the United States and the potential to intervene to reduce the prevalence of conduct disorder."
Conduct disorder, as defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) of the American Psychiatric Association, is characterized by persistent patterns of child or adolescent behavior involving aggression or other violations of age-appropriate norms that cause significant clinical impairment. Behaviors include bullying others, getting into fights, fighting with a weapon, cruelty to people or animals, stealing with confrontation, forced sex, property destruction, theft and rule breaking.
To study the prevalence of conduct disorder associated with migration from Mexico to the United States, UC Davis and RAND Corporation researchers assessed conduct disorder symptoms across four groups of people of Mexican origin with increasing levels of exposure to American culture: nonimmigrant households in Mexico with no exposure to the United States, Mexicans from migrant households who lived in Mexico until age 15, children of Mexican migrants raised in the United States and Mexican-American children of U.S.-born parents. The researchers obtained data by conducting face-to-face interviews with nearly 1,800 adults aged 18 to 44 years in the household populations of Mexico and those of Mexican descent in the United States.
The study found that, compared to the general population of Mexico with no history of migration to the United States and Mexicans from migrant households who lived in Mexico until age fifteen, 11.5 percent of Mexican-American children with at least one U.S.-born parent met the DSM-IV criteria for conduct disorder. This level is close to that of the non-Mexican-American, U.S.-born sample prevalence of 10.6 percent.
"We found a striking epidemiological pattern with differences across generations that are both larger in magnitude and more narrow in scope that anyone expected," said Joshua Breslau, a researcher with the RAND Corporation in Pittsburgh who conducted the study while an assistant professor of internal medicine at UC Davis Health System. "Future studies will be needed to identify the specific environmental factors that contribute to these differences."
Other researchers in the study include Daniel J. Tancredi, Richard Kravitz and Ladson Hinton from UC Davis School of Medicine; Guilherme Borges, Corina Benjet and Maria Elena Medina-Mora from the National Institute of Psychiatry in Mexico City; Kenneth S. Kendler from the Medical College of Virginia; and William Vega from the University of Southern California.
The research was supported by grants from the National Institute of Mental Health, National Institutes of Health grant to the UC Davis Clinical and Translational Science Center, and the University of California Migration and Health Research Center.