Mechanisms of mental illness anti-stigma messaging matter: Leveraging mental health communication inequities among Latinx populations to understand what works and what we can do better

BACKGROUND

Since 1950, public communication about the neurobiological-psychosocial basis of mental illness from the diathesis-stress model has promoted reception to treatment yet violent/dangerous stereotypes have increased during this period. Moreover, public mental health communication efforts have predominantly diffused in English-language media, excluding Spanish/Latinx media and its consumers from these efforts. To inform future mental health communication strategies, this study leverages high versus low diffusion of public mental health communication across English and Spanish/Latinx media to examine public mental health communication effects on stigma and treatment beliefs via neurobiological-psychosocial beliefs.

METHODS

A quota sample of 2058 U.S.-based Latinx residents ages 13-86 with diverse language/cultural media preferences was recruited to self-complete a survey about mental health information acquisition in 2021. Assessments ascertained frequency of Spanish/Latinx and English media use and mental health content scanning and seeking (α = 0.86-0.94); and items from the General Social Survey about mental illness neurobiological-psychosocial causal beliefs (α = 0.72)-genetics, brain chemistry, environment, stress; treatment beliefs-mental illness improves with treatment or on its own; and stigma beliefs-violent/dangerous and bad character stereotypes and unwillingness to socialize with a person with mental illness. Structural equation models estimated total, direct, and indirect effects of Spanish/Latinx and English media exposures on treatment and stigma beliefs via neurobiological-psychosocial beliefs, net individual/family factors.

RESULTS

Spanish/Latinx media reduced, while English media increased, neurobiological-psychosocial beliefs (p < 0.01). Neurobiological-psychosocial beliefs, in turn, increased treatment and stigma beliefs (p < 0.01), simultaneously. Indirect pathways were also significant (p < 0.05). Proportion mediated on treatment beliefs was one-third for Spanish/Latinx and two-thirds for English media. Proportion mediated on stigma beliefs for all media exposures averaged ≥1.

CONCLUSIONS

While consumers of Spanish/Latinx media report lower neurobiological-psychosocial knowledge that impedes treatment beliefs, consumers of English media report greater neurobiological-psychosocial and treatment knowledge and, consequently, more stigma. Innovation in public mental health communication is needed to counter stigma and health inequity.

The impact of adjusting for pure predictors of exposure, mediator, and outcome on the variance of natural direct and indirect effect estimators

It is now well established that adjusting for pure predictors of the outcome, in addition to confounders, allows unbiased estimation of the total exposure effect on an outcome with generally reduced standard errors (SEs). However, no analogous results have been derived for mediation analysis. Considering the simplest linear regression setting and the ordinary least square estimator, we obtained theoretical results showing that adjusting for pure predictors of the outcome, in addition to confounders, allows unbiased estimation of the natural indirect effect (NIE) and the natural direct effect (NDE) on the difference scale with reduced SEs. Adjusting for pure predictors of the mediator increases the SE of the NDE's estimator, but may increase or decrease the variance of the NIE's estimator. Adjusting for pure predictors of the exposure increases the variance of estimators of the NIE and NDE. Simulation studies were used to confirm and extend these results to the case where the mediator or the outcome is binary. Additional simulations were conducted to explore scenarios featuring an exposure-mediator interaction as well as the relative risk and odds ratio scales for the case of binary mediator and outcome. Both a regression approach and an inverse probability weighting approach were considered in the simulation study. A real-data illustration employing data from the Canadian Study of Health and Aging is provided. This analysis is concerned with the mediating effect of vitamin D in the effect of physical activity on dementia and its results are overall consistent with the theoretical and empirical findings.

Does food vendor density mediate the association between neighborhood deprivation and BMI?: a G-computation mediation analysis

BACKGROUND

In previous research, neighborhood deprivation was positively associated with body mass index (BMI) among adults with diabetes. We assessed whether the association between neighborhood deprivation and BMI is attributable, in part, to geographic variation in the availability of healthful and unhealthful food vendors.

METHODS

Subjects were 16,634 participants of the Diabetes Study of Northern California, a multiethnic cohort of adults living with diabetes. Neighborhood deprivation and healthful (supermarket and produce) and unhealthful (fast food outlets and convenience stores) food vendor kernel density were calculated at each participant's residential block centroid. We estimated the total effect, controlled direct effect, natural direct effect, and natural indirect effect of neighborhood deprivation on BMI. Mediation effects were estimated using G-computation, a maximum likelihood substitution estimator of the G-formula that allows for complex data relations such as multiple mediators and sequential causal pathways.

RESULTS

We estimated that if neighborhood deprivation was reduced from the most deprived to the least deprived quartile, average BMI would change by -0.73 units (95% confidence interval: -1.05, -0.32); however, we did not detect evidence of mediation by food vendor density. In contrast to previous findings, a simulated reduction in neighborhood deprivation from the most deprived to the least deprived quartile was associated with dramatic declines in both healthful and unhealthful food vendor density.

CONCLUSIONS

Availability of food vendors, both healthful and unhealthful, did not appear to explain the association between neighborhood deprivation and BMI in this population of adults with diabetes.

Mediation misgivings: ambiguous clinical and public health interpretations of natural direct and indirect effects

Recent methodological innovation is giving rise to an increasing number of applied papers in medical and epidemiological journals in which natural direct and indirect effects are estimated. However, there is a longstanding debate on whether such effects are relevant targets of inference in population health. In light of the repeated calls for a more pragmatic and consequential epidemiology, we review three issues often raised in this debate: (i) the use of composite cross-world counterfactuals and the need for cross-world independence assumptions; (ii) interventional vs non-interventional identifiability; and (iii) the interpretational ambiguity of natural direct and indirect effect estimates. We use potential outcomes notation and directed acyclic graphs to explain 'cross-world' assumptions, illustrate implications of this assumption via regression models and discuss ensuing issues of interpretation. We argue that the debate on the relevance of natural direct and indirect effects rests on whether one takes as a target of inference the mathematical object per se, or the change in the world that the mathematical object represents. We further note that public health questions may be better served by estimating controlled direct effects.