12-month prevalence of DSM-III-R psychiatric disorders among Mexican Americans: nativity, social assimilation, and age determinants.

The burden of disease attributable to mental illnesses has major costs and human services implications in the United States. Mexican Americans compose two thirds of the nation's largest and fastest-growing minority group, Latinos. We report 12-month DSM-III-R psychiatric disorder rates among Mexican Americans derived from a population survey of immigrants and US-born adults of Mexican origin conducted in rural and urban areas of central California. Rates of 12-month total mood, anxiety, and substance disorders were 14.2% for immigrant women, 12.6% for immigrant men, 27.8% for US-born women, and 27.2% for US-born men. For immigrants, younger age of entry and longer residence in the United States were associated with increased rates of psychiatric disorders. Three dominant explanations are reviewed to explain these differences: selection, social assimilation and stress, and measurement artifact. Our results and other research studies collectively support a social assimilation explanation based on aversive impact on health behaviors and protective resources such as families. Greater social assimilation increases psychiatric morbidity, with rates for subjects who are US-born of Mexican origin approximately the same as rates for the US general population.