Context Twin studies suggest that conduct disorder (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.
Objectives To examine variation in the prevalence of CD associated with migration from Mexico to the United States and to determine whether this variation is similar for aggressive and nonaggressive CD symptoms and symptom profiles.
Design The prevalences of CD, different types of CD symptoms, and CD symptom profiles were compared across 3 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 US-born parents.
Setting General population surveys conducted in Mexico and the United States using the same diagnostic interview.
Participants Adults aged 18 to 44 years in the household population of Mexico and the household population of people of Mexican descent in the United States.
Main Outcome Measures Conduct disorder criteria, assessed using the World Mental Health version of the Composite International Diagnostic Interview.
Results Compared with the risk in families of origin of migrants, risk of CD was lower in the general population of Mexico (odds ratio [OR], 0.54; 95% CI, 0.19-1.51), higher in children of Mexican-born immigrants who were raised in the United States (OR, 4.12; 95% CI, 1.47-11.52), and higher still in Mexican-American children of US-born parents (OR, 7.64; 95% CI, 3.20-18.27). The association with migration was markedly weaker for aggressive than for nonaggressive symptoms.
Conclusions The prevalence of CD increases dramatically across generations of the Mexican-origin population after migration to the United States. This increase is of larger magnitude for nonaggressive than for aggressive symptoms, consistent with the suggestion that nonaggressive symptoms are more strongly influenced by environmental factors than are aggressive symptoms.