BackgroundSince 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. MethodsA 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. ResultsSpanish/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. ConclusionsWhile 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.