There are some important strengths, as well as limitations, in our study. In particular, the use of a family-based design protects against population stratification. With the exception of the Sakai (2010) study, prior analyses used primarily subjects of one ethnicity. While many ethnicities have been represented, including European American, Japanese, and African American populations, our study represents one of the first to include subjects of two ethnicities. Furthermore, the inclusion of the Hispanics provided a larger sample size. While it is possible that distributional differences in CD and AAD may be culturally influenced and affect our results, we do not believe this is the case because the distributions for CD and adult AAD between EAs and Hispanics were comparable in our samples. In addition, we used a continuous variable to examine CD and AAD, rather than dichotomous variable. Continuous variables provide a more accurate estimate of the phenotype, as dichotomizing variables can cause a loss of information. Moreover, our incorporation of both AAD symptoms is unique. This study, however, is not without limitations. Specifically, there is low power to detect
