BMC Public Health 2007, 7:21 http://www.biomedcentral.com/1471-2458/7/21 they had something to say, told them when they did a good job, always wanted them to do their best, and noticed when they were in a bad mood". Thus, teachers and school counselors are important sources of support, and need to be trained to recognize symptoms and risk factors of depression. They also need to be given the time to pay attention to individual students. A multivariate analyses taking into account existing inter- actions between socio-economic status, perceived support and ethnicity provided a profile of depressive symptoms that was even more detailed. When we examined different strata of household income and support, either at home or at school, Latino ethnicity emerged as risk factor for depressive symptoms only among the strata with higher income and high support at home and at school. While this finding is counterintuitive at first, it suggests that high economic status and social support are protective factors only among Non-Latino Whites. We have not been able to find any literature that is investigating this hypothesis. An alternative interpretation relates to the association between depressive symptoms and perceived discrimina- tion. Several studies suggest that higher income is associ- ated with more perceived discrimination and that discrimination is a risk factor for depression [21,22]. Since CHIS does not assess perceived discrimination, we were not able to examine this relationship. We found no ethnic differences between Latino and Non-Latino Whites in the prevalence of depressive symptoms in the strata with low income or low social support at home Although our data suggest several correlations between socio-demographic characteristics, social support and depressive symptoms, the causal nature of these relation- ships is ambiguous given the cross sectional study design. As pointed out by others [8], depressed adolescents may be less inclined to form supportive relationships with par- ents, teachers or peers, and less likely to perceive relation- ships as supportive, and to report supportive relationships. Another limitation of our data set is that several variables that have been shown to be risk factors for depression, such as stressful life events [9], perceived discrimination and low self esteem [21-23], being involved in bullying either as a perpetrator or as a victim [5], affiliation with high-versus low status peer crowd, negative or positive qualities of friendships, and presence or absence of romantic relationships [24] were not availa- ble. Finally, as in many other studies, our measure of acculturation may not have captured aspects of the accul- turation process that are related to depression. Although we attempted to include all data related to the accultura- tion experience that were available in this data set in developing an acculturation scale, and although we used a method that has the advantage of not making inappro- priate statistical assumptions, the dichotomized accultur- ation variable that we created was almost identical to a simple dichotomization based on country of birth (US versus other). Finally, our sample of low acculturation Latino respondents was relatively small and given that most Latinos living in California are from Mexico, find- ings may not be generalizable to those with different her- itage. However, despite these limitations, our analysis adds some information to the sparse literature on depres- sion among ethnically diverse adolescents. Conclusion Our findings suggest that differences in depressive symp- toms between Non-Latino Whites and Latino adolescents disappear at least in some strata after adjusting for socio- demographic and social support variables and gave rise to some interesting hypotheses regarding modifiers of depression such as household income, social support and gender. These hypotheses should be further investigated in order to identify groups that are at high risk for depres- sion and could benefit from interventions. Competing interests The authors declare that they have no competing interests. Authors' contributions RTM analyzed the data and participated in the interpreta- tion of the results and the writing of the final version of the manuscript. MB, NK, CM developed the research ques- tion, performed preliminary analyses and wrote a few sec- tions of the manuscript as part of a class assignment. AEM participated in the interpretation of the results and wrote large parts of the final version of the manuscript. All authors approved the final version of the manuscript. Acknowledgements MB, NK and CM were students in the MPH program during preparation of this manuscript. This research was conducted during Dr. Maxwell's 12 months Visiting Professorship at the School of Public Health, Department of Public Health Medicine, University of Bielefeld, funded by the German Academic Exchange Service (DAAD). References 1. Üstün TB, Chatterji S: Global Burden of Depressive Disorders and Future Projections. In Depression: Social and Economic Time- bomb Edited by: Dawson A, Tylee A. London , BMJ Books ; 2001. 2. The changing rate of major depression. Cross-national com- parisons. Cross-National Collaborative Group. Jama 1992, 268(21):3098-3105. 3. Birmaher B, Ryan ND, Williamson DE, Brent DA, Kaufman J, Dahl RE, Perel J, Nelson B: Childhood and adolescent depression: a review of the past 10 years. Part I. J Am Acad Child Adolesc Psychi- atry 1996, 35(11):1427-1439. 4. U.S. Department of Health and Human Services Mental Health: A Report of the Surgeon General. Rockville, MD , U.S. Depart- ment of Health and Human Services, Substance Abuse and Mental Health Services Administration, Center for Mental Health Services, National Institutes of Health, National Institute of Mental Health; 1999. 5. Saluja G, Iachan R, Scheidt PC, Overpeck MD, Sun W, Giedd JN: Prevalence of and risk factors for depressive symptoms Page 8 of 9 (page number not for citation purposes)