According to a study in the December issue of Archives of General Psychiatry, one of the JAMA/Archives journals, across generations of Mexican-origin population after migration to the U.S., the prevalence of conduct disorder (CD) seems to have considerably increased, although this rise was seen more for nonaggressive than aggressive symptoms of CD.

The researchers explain:

“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. 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.”

Joshua Breslau, Ph.D., Sc.D., of the RAND Corporation, Pittsburgh, and colleagues conducted a study in order to analyze variation in the prevalence of conduct disorder connected with migration from Mexico to the U.S.. The researchers compared different types of CD symptoms, the prevalence of conduct disorder as well as CD symptom profiles across three generations of individuals of Mexican origin with rising levels of exposure to American culture:

  • Children of Mexican migrants raised in the U.S.
  • Mexican-American children of parents born in the U.S.
  • families of origin of migrants (residing in Mexico)

The team gathered data using the same face-to-face interview with individuals aged between 18 to 44 years in the household population of individuals of Mexican origin in the U.S., and the household population of Mexico.

They discovered that the risk of CD was lower in the general population of Mexico (Mexicans living in non-migrant households) compared with the risk in families of origin of migrants. However, in children of Mexican-born immigrants who were raised in the U.S., the risk was higher. Furthermore, they discovered that the highest risk of conduct disorder was in Mexican-American children whose parents were born in the U.S., and that the connection of CD with migration was higher for nonaggressive symptoms than for aggressive symptoms.

The researchers state:

“The results suggest that there is a large difference in risk for CD between Mexicans in Mexico and people of Mexican descent 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.”

They conclude:

“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. 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.”

Written by Grace Rattue