PTSD Mediated the Link between Childhood Mistreatment and Substance Use in Latinx Nationwide: Discrimination in an Omitted-Variable Bias

Background: Childhood mistreatment (CM) has been associated with adult posttraumatic disorder (PTSD) and substance use disorders (SUD) in the general population. Few studies have explored the complex association among Latinx nationwide, a minority population facing considerable discrimination and, as a result, disproportionately experience disparities in access to culturally-appropriate behavioral healthcare. There is a great need to better understand: a) the relationship between CM, PTSD, and SUD in Latinx; b) the role of perceived discrimination; and c) potential differences between U.S.-born and immigrant Latinxs in the United States. This theory-driven, cross-sectional study evaluated a theory-driven conceptual model with a specific focus on the impact of perceived discrimination, which may interfere with these associations.

Methods: Using a nationally representative sample, the National Latino and Asian American Study (NLAAS), structural equation modeling (SEM) was used to evaluate the mediation of PTSD in the CM-SUD link, adjusting for, or omitting discrimination and other sociodemographic variables that are known predictors of Latinx behavioral health. Multi- subsample analyses were then conducted to review nativity differences (U.S.-born = 924, 43%, and immigrant = 1,630, 57%). The double test was expected for better understanding of discrimination, via the lens of the omitted-variable bias (OVB) assumption, a statistical phenomenon whereby variable associations are confounded by covariates that were not included in the analysis. Results: The fully specified final model (Model-1, covariates adjusted) failed to show a significant mediation of PTSD in the tested link, but a direct detrimental effect group of discrimination, for all Latinx. The mediation was only supported, when treating discrimination and other covariates as omitted variables (Model-5), which also showed additional direct and indirect effect of CM on SUD. In subsample analyses, models of U.S.-born and immigrant-Latinx subpopulations were identical but showed nativity differences when omitting covariates.

Conclusions and Implications: When discrimination and other covariates were fully adjusted, Latinx exposed to trauma were more likely to develop SUD in adulthood, regardless of when traumatic exposure occurred. This unexpected finding challenges theories explaining the CM-SUD connection, suggesting possible model misspecifications of parametric SES; namely, omitting the unique impact of perceived discrimination in Latinx can lead to biased results. From a clinical standpoint, both trauma and discrimination must be addressed when assessing Latinx behavioral health.