The analytical framework behind the study is the syndemic approach, a concept introduced by medical anthropologist Merrill Singer in the late 1990s. Syndemic theory holds that diseases do not merely coexist; they interact synergistically within populations shaped by poverty, inequality, and structural violence, producing a health burden greater than the sum of individual conditions. The framework was originally developed to explain how HIV/AIDS, substance use, and violence reinforced one another in marginalized communities, and it has since been applied to depression and diabetes among populations affected by migration and urban violence in Chicago. What makes the new Mexican study distinctive is its application of this lens to nationally representative data, treating cardiometabolic and cardio-renal disease clusters not as isolated diagnoses but as interconnected systems that amplify mental health risk.

Methodologically, the researchers pooled three independent cross-sectional waves of ENSANUT, combining 13,402 adults from 2021, 11,913 from 2022, and 6,772 from 2023 into a single sample of 32,087 people aged 20 and older. Because each annual wave is an independent, nationally representative sample with no repeated individuals, the pooled dataset increases statistical power without introducing duplicate observations. The survey weights, strata, and clusters built into the complex sampling design were applied throughout, allowing the results to represent roughly 125 million Mexicans living in private dwellings. Response rates were 84 percent in 2021 and 73 percent in 2022, and the 2023 wave followed the same sampling framework, ensuring comparability across years.

Depressive symptoms were measured with the abbreviated version of the Centre for Epidemiologic Studies Depression Scale, a seven-item instrument validated for the Mexican population. The researchers applied a cut-off of nine or more points for adults aged 20 to 59 and five or more points for those aged 60 and above, following previous validation studies. Suicidal ideation was captured through a self-reported item in the adult questionnaire asking whether participants had experienced thoughts of ending their life during a defined recall period. Rather than analyzing these outcomes separately, the team constructed a four-category multinomial outcome: depressive symptoms alone, suicidal ideation alone, both conditions, and neither. This design allowed them to distinguish between people who experience distress in one form and those who carry the heaviest combined burden.

The statistical engine of the study was multinomial logistic regression, which yields relative risk ratios expressing the probability of belonging to each outcome category compared with the reference group of adults reporting neither condition. Two interaction terms were specified in advance on theoretical grounds rather than discovered through exploratory testing. The first was a three-way interaction among diabetes, hypertension, and obesity, representing cardiometabolic multimorbidity. The second was a two-way interaction between chronic kidney disease and cardiovascular disease, representing the cardio-renal axis of advanced target-organ damage. The model showed significant overall fit with a McFadden pseudo R-squared of 0.11, and adding the interaction terms improved the log-likelihood from minus 24,742.1 to minus 24,293.4, a difference that was statistically significant.

The results of these interaction tests are striking. Adults living with all three cardiometabolic conditions had more than double the relative probability of suicidal ideation compared with those without them, and more than four times the probability of experiencing depressive symptoms and suicidal thoughts together. The cardio-renal combination proved even more potent: people with both chronic kidney disease and cardiovascular disease showed a 3.55-fold higher relative probability of suicidal ideation and a 6.78-fold higher probability of the combined outcome. These estimates exceeded those for cardiometabolic multimorbidity, marking the convergence of renal and cardiovascular disease as the single most dangerous clinical configuration in the analysis. The effect remained stable and significant across all model specifications, including those adjusted for sociodemographic and lifestyle variables.

Sociodemographic patterns added a second layer of vulnerability. Women accounted for 65.8 percent of depressive symptom cases and 71.5 percent of cases where depression coexisted with suicidal ideation, and being female more than doubled the relative probability of depressive symptoms. Age produced a striking divergence: adults aged 60 and older made up nearly half of all depressive symptom cases, with a probability more than four times higher than younger adults, yet suicidal ideation was concentrated overwhelmingly among people aged 20 to 59, who accounted for 92.5 percent of such reports. Hypertension was present in 45.4 percent of those with depressive symptoms and 57.8 percent of those with both outcomes, while obesity doubled its prevalence in the coexistence group compared with the general population.

Social and behavioral conditions carved the gradient even deeper. Adults in the highest economic well-being tertile had roughly half the probability of depressive symptoms and less than half the probability of the combined outcome compared with the poorest tertile, a finding consistent with decades of research linking income to mental health. Urban residence increased the likelihood of suicidal ideation by 43 percent and of the combined outcome by 58 percent, a pattern the authors attribute to the concentration of psychosocial stressors such as social fragmentation, economic inequality, and exposure to violence in cities. Non-smokers showed consistently lower probabilities of adverse outcomes, and alcohol abstinence was associated with a significant reduction in the probability of coexisting depression and suicidal thoughts. The authors caution, however, that the cross-sectional design prevents any claim about causality or direction, since it is impossible to determine whether depression precedes hypertension or follows it.

The public health implications are considerable. The authors argue that screening for depressive symptoms and suicidal ideation should be systematically integrated into chronic disease management programs, particularly for patients with cardiometabolic and cardio-renal multimorbidity, and they point to task-shifting strategies involving trained primary care personnel and community health workers as a feasible route to earlier detection. They also emphasize that similar syndemic patterns have been documented in Brazil and Colombia, suggesting that the Mexican findings reflect broader structural dynamics across Latin America and offering opportunities for regional policy learning. The study’s limitations, including self-reported symptoms that may underestimate suicidal ideation due to stigma and the absence of contextual variables such as community violence and discrimination, point toward future longitudinal and multilevel research. Still, the central message stands: mental health care in Mexico cannot remain separate from chronic disease care, because the two are bound together in a web of biological and social amplification that no single-service intervention can untangle.

Subject of Research: Syndemic interactions between chronic diseases, social conditions, and mental health in Mexican adults

Article Title: Depressive symptoms and suicidal ideation among Mexican adults in a syndemic analysis of chronic comorbidities and social conditions

Article References: Hernández-Álvarez, A., Rodríguez-Hernández, J. M., Fernández-Ortiz, Y. N., Urrego-Ricaurte, D. C., & Campuzano-Rincón, J. C. (2026). Depressive symptoms and suicidal ideation among Mexican adults in a syndemic analysis of chronic comorbidities and social conditions. Discover Social Science and Health, 6(1), Article 95. https://doi.org/10.1007/s44155-026-00425-3

Image Credits: AI Generated

DOI: 10.1007/s44155-026-00425-3

Keywords: depression, suicidal ideation, syndemic, multimorbidity, diabetes, hypertension, obesity, chronic kidney disease, cardiovascular disease, social determinants of health, Mexico, ENSANUT