Study examines prevalence of conduct disorder among families of Mexican migrants in the US

The prevalence of conduct disorder (CD) appears to have increased substantially across generations of the Mexican-origin population after migration to the United States, however this increase was observed more for nonaggressive than aggressive symptoms of CD, according to a report in the December issue of Archives of General Psychiatry.

"Conduct disorder (CD) is defined in the DSM-IV by persistent patterns of child or adolescent behavior involving aggression or other violations of age-appropriate norms that cause significant clinical impairment," the authors write as background information in the article. "Twin studies suggest that CD is under substantial genetic influence, which is stronger for aggressive than for nonaggressive symptoms. Studies of migrating populations offer an alternative strategy for separating environmental and genetic influences on psychiatric disorders."

To examine variation in the prevalence of CD associated with migration from Mexico to the United States, Joshua Breslau, Ph.D., Sc.D., of the RAND Corporation, Pittsburgh, and colleagues compared the prevalence of CD, different types of CD symptoms and CD symptom profiles across three generations of people of Mexican origin with increasing levels of exposure to American culture: families of origin of migrants (residing in Mexico), children of Mexican migrants raised in the United States, and Mexican-American children of U.S.-born parents. Data were collected using the same face-to-face interview with adults age 18 to 44 years in the household population of Mexico and the household population of people of Mexican decent in the United States.

The authors found that compared with the risk in families of origin of migrants, risk of CD was lower in the general population of Mexico (Mexicans living in non-migrant households), but higher in children of Mexican-born immigrants who were raised in the United States. The highest risk of CD was found in Mexican-American children of U.S.-born parents. The authors also found that the association of CD with migration was much lower for aggressive symptoms than for nonaggressive symptoms.

"The results suggest that there is a large difference in risk for CD between Mexicans in Mexico and people of Mexican decent in the United States. Only 2 percent of people in families of migrants met DSM-IV criteria for CM, but 11.5 percent of U.S.-born Mexican-Americans with at least one U.S.-born parent met these criteria," the authors write.

"In this study, comparisons across representative samples of successive generations within a migrating population suggest that the environmental influence on CD is large but restricted to certain subtypes of the disorder," the authors conclude. "Future studies may be able to identify the specific genetic and environmental factors involved in this complex epidemiologic shift in psychiatric morbidity, particularly if they include samples of migrant families with members in both the sending and receiving communities."