BMC Public Health 2007, 7:21 http://www.biomedcentral.com/1471-2458/7/21 FDiigsturribeu1tion of the acculturation index (Kernel density plot) Distribution of the acculturation index (Kernel density plot). arity problems were detected for the analyzed variables. We also examined the effect of acculturation in the Latino subsample, using a continuous acculturation score (data not shown) and in a second step as a dichotomous varia- ble. Finally, the possibility of effect modification between ethnic background and other variables was investigated. The modeling strategy followed Hosmer and Lemeshow [18]. All variables were included in a multiple logistic regression model. All two-ways interactions were investi- gated in separate steps with the main effects model. Inter- actions significant at the 0.05 level (based on Wald-test) were included jointly in the preliminary final model. The final model was obtained by removing effects which were not significant at the 0.05 level. For variables with effect modification the effect of ethnic background was calcu- lated for different strata. All analyses were performed using SPSS 12.0. Results Description of the sample The total sample consisted of 3196 adolescents: 2071 Non-Latino White youth, 865 Latino youth in the high acculturation category and 260 in the low acculturation category. The three groups were significantly different with respect to most socio-demographic characteristics (see Table 2). Latino youth came more frequently from lower income households, and reported lower support at home or at school. The low acculturation Latino group was the most disadvantaged in terms of social support and income. However, more Latino youth in the low accultur- ation group came from two parent households as com- pared to high acculturation Latinos and Non-Latino Whites. Characteristics associated with depressive symptoms Scores on the 8-item CES-D Scale ranged from 0–24, with a mean score of 4.4 and standard deviation of 3.7. A total of 232 adolescents (7.3% of the sample) had scores >10 and were classified as having symptoms of depression (see Table 3). Based on univariate analysis, a significantly larger proportion of Latino youth had depressive symp- toms as compared to Non-Latino Whites (10.5% versus 5.5%, p < 0.001). Although more low acculturation Lati- nos had symptoms of depression than high acculturation Latinos (13.1% versus 9.7%), this difference was not sta- tistically significant (chi-square, p = 0.12). Females, youth living in households below 200% poverty level, those liv- ing in a one parent household and those who received low support at home and at school were significantly more likely to have symptoms of depression. Age was not asso- ciated with symptoms of depression in this sample. In multivariate analysis, not accounting for effect modifi- cation, the impact of ethnic background and acculturation decreased as compared to univariate analysis (Table 3, columns 4 and 5). In this analysis, the odds of depressive symptoms were only increased among low acculturation Latinos as compared to Non-Latino Whites. Poverty level and low level of support at home no longer emerged as independent predictors of depressive symptoms. In this analysis, the most important predictors of depressive symptoms were low support at school, female gender, being classified as low acculturation Latino and coming from a one parent household. Characteristics associated with depressive symptoms in the Latino subsample We examined independent predictors of depressive symp- toms among Latinos by limiting the analysis to the Latino subsample. Similar to the multivariate analysis in the whole sample shown in Table 3, female gender and low support at school emerged as risk factors in the Latino subsample (Table 4). In the low acculturation group the odds of depressive symptoms were 50% higher than in the high acculturation group, but the effect did not reach sta- tistical significance. There was no substantial change in effects of other variables after the inclusion of the accul- turation variable in the joint model, only the impact of poverty level slightly decreased. There was also no evi- dence of effect modification in the Latino subsample which was assessed by significance of interaction terms (data not shown). Page 4 of 9 (page number not for citation purposes)