SINCE 1970, more than 5 million Mexicans have immigrated to the United States, the largest number of immigrants from one country to the United States in recent history. People of Mexican descent now make up almost one third of the total population of Texas and California.¹

The study by Vega et al reported in this issue of the ARCHIVES is an important and timely piece, coming when Mexican immigrants in California are the target of adverse societal attitudes and governmental policies affecting benefits, university access, and bilingualism. Paradoxically, the study shows that despite socioeconomic disadvantages, Mexican immigrants have a much better mental health profile than people of Mexican descent born in the United States. Carried out on a specific population in northern California, the study was elegantly designed and employed state-of-the-art methods and instrumental measures that were further refined during the study. The study's major finding, that place of birth had a more profound influence on the prevalence of psychiatric disorders than traditional demographic risk factors such as age, sex, or socioeconomic status, is intriguing. According to these data, for virtually each disorder studied, Mexican immigrants had about half the prevalence rate of people of Mexican descent born in the United States. The study illustrates the importance of cross-cultural research in advancing our knowledge of risk and protective factors for mental disorders and reminds us that the study of the mental disorders of specific ethnic groups can generate hypotheses that apply to general psychiatry. Also, the relevance of international collaboration in psychiatric research is shown by the successful use of the Mexico City sample to help interpret the results of the study.