Simple Blood Sugar and Fat Measure Linked to Thinking Problems in Early Schizophrenia

A routine blood test may offer a surprisingly simple window into one of the most disabling and least treatable aspects of schizophrenia: cognitive impairment. A large cross-sectional study of 498 patients experiencing their first episode of schizophrenia and who had never yet taken antipsychotic medication reports that a common metabolic marker, the triglyceride-glucose index, tracks closely with how poorly patients perform on standardized tests of memory and attention. The findings, published in BMC Psychiatry by a team from the First Hospital of Shanxi Medical University in Taiyuan, China, suggest that the metabolic disturbances long associated with serious mental illness may be intertwined with brain function from the very start of the disorder, before any drug treatment can muddy the picture.

The marker in question, known as the triglyceride-glucose or TyG index, is calculated from fasting levels of triglycerides and glucose, the two values captured in an ordinary lipid and blood sugar panel. In recent years the TyG index has gained popularity among researchers as a cheap, convenient proxy for insulin resistance, the condition in which the body’s tissues respond weakly to the hormone insulin and in which glucose metabolism becomes progressively dysregulated. Insulin resistance is highly prevalent in people with schizophrenia and is usually attributed to antipsychotic medications, which are notorious for driving weight gain and metabolic syndrome. What makes the new study notable is that its participants were drug-naïve: no patient had yet been exposed to antipsychotics, removing the most obvious confounder and allowing the researchers to ask whether insulin resistance is linked to cognition independently of treatment.

To probe that question, the team recruited 498 first-episode, drug-naïve schizophrenia patients between the ages of 16 and 48, along with 201 healthy controls matched for sex and age. Each participant underwent fasting blood sampling for the calculation of the TyG index, a clinical assessment of psychiatric symptoms using the Positive and Negative Syndrome Scale, and a comprehensive cognitive evaluation with the Repeatable Battery for the Assessment of Neuropsychological Status, a widely used instrument that scores five cognitive domains: immediate memory, visuospatial and constructional ability, attention, language, and delayed memory.

The statistical analysis, which included generalized linear models controlling for sociodemographic and clinical confounders as well as smoothed curve fitting, revealed a consistent and striking pattern. Higher TyG index values were significantly associated with lower performance in three of the five cognitive domains and in overall cognition. Specifically, the index showed negative associations with immediate memory, attention, and delayed memory, as well as with the total RBANS score, with all of these relationships reaching strong statistical significance. The reported standardized coefficients were β = -7.77 for immediate memory, β = -9.09 for attention, and β = -11.39 for delayed memory, alongside β = -7.20 for the total score, with all p values below 0.001. Notably, visuospatial ability and language did not show significant associations, hinting that metabolic factors may preferentially erode memory systems and attentional control rather than cognition as a whole.

When the researchers divided patients into quartiles according to their TyG index, the dose-response relationship became even clearer: patients in the highest quartile, meaning the most insulin-resistant, scored significantly worse across the affected domains than those in the lowest quartile. Importantly, stratified analyses showed that the association held steady across subgroups defined by sex, age, education level, smoking status, drinking status, and body mass index, with no significant interactions. In other words, the link between insulin resistance and cognitive impairment was not simply an artifact of one subgroup being older, heavier, or more likely to smoke. This robustness across strata strengthens the case that the TyG index captures something biologically meaningful about the relationship between metabolism and cognition in schizophrenia.

Why would insulin resistance affect the brain at all? A growing literature in neuroscience offers several plausible mechanisms. Insulin signaling in the brain is known to influence synaptic plasticity, the process by which connections between neurons are strengthened or weakened during learning and memory formation. In animal models, brain insulin resistance impairs hippocampal function, and the hippocampus is precisely the structure most heavily involved in the immediate and delayed memory domains that showed the strongest associations in this study. Insulin resistance also tends to travel with chronic low-grade inflammation, oxidative stress, and vascular dysfunction, all of which can damage the microvasculature and white matter that support fast, efficient attention and memory retrieval. Some researchers have even begun to describe Alzheimer’s disease as a form of brain diabetes, and the present findings suggest that metabolic dysregulation in schizophrenia may operate through overlapping pathways.

There is also an intriguing possibility about direction of causality. Because these patients were in the first episode of their illness and had never received antipsychotics, the metabolic abnormalities they display cannot be blamed on medication. Some studies have found evidence of insulin resistance even in individuals at clinical high risk for psychosis and in unaffected close relatives, fueling the hypothesis that shared genetic or developmental vulnerabilities predispose some people to both psychosis and metabolic dysfunction. Whether elevated insulin resistance contributes to the severity of cognitive impairment, whether the neurobiology of psychosis drives metabolic derangement, or whether both arise from a common underlying mechanism remains an open question that cross-sectional data cannot resolve.

That limitation is one the authors themselves emphasize. The study’s design captures a single moment in time, so it can establish association but not causation, and the retrospective trial registration is noted in the paper. Longitudinal follow-up will be needed to determine whether patients with high TyG indices at first presentation go on to experience steeper cognitive decline, and whether interventions that improve insulin sensitivity, such as lifestyle modification, metformin, or newer metabolic agents, can slow or prevent that trajectory. The potential payoff, however, is substantial, because cognitive impairment in schizophrenia is a major driver of long-term disability and currently has no approved pharmacological treatment.

From a practical standpoint, the appeal of the TyG index lies in its accessibility. Unlike direct measures of insulin resistance such as the hyperinsulinemic-euglycemic clamp or more elaborate indices like HOMA-IR, which require insulin assays and additional computation, the TyG index needs only the fasting triglyceride and glucose values that are routinely ordered in almost any clinical workup. If future prospective studies confirm its predictive value, clinicians could conceivably use it as a routine screening tool, flagging newly diagnosed schizophrenia patients with elevated metabolic indices for closer neuropsychological monitoring and early metabolic intervention. The authors suggest that routine assessment of the TyG index may help identify cognitive impairment in first-episode, drug-naïve patients, positioning the measure as a candidate early-warning signal rather than a diagnostic test.

The study also carries a broader message about how psychiatry and metabolic medicine are converging. Once considered separate branches of medicine, the two fields increasingly share mechanistic ground, with insulin signaling, inflammation, and vascular health emerging as common threads running through conditions as different as psychosis and dementia. A cheap blood-derived number that correlates with memory and attention in young people at the start of a psychotic illness is a vivid illustration of that convergence. It remains to be seen whether lowering the TyG index would raise cognitive scores, but the study provides a concrete, testable hypothesis and, if confirmed in longitudinal work, an unusually low-cost target for protecting the brains of people with schizophrenia at the earliest and most treatable stage of their illness.

Subject of Research: The association between insulin resistance, measured by the triglyceride-glucose index, and cognitive impairment in first-episode drug-naïve schizophrenia

Article Title: The association between triglyceride-glucose index and cognitive impairment in patients with first-episode drug-naïve schizophrenia: a large-scale cross-sectional study

Article References: Hu, C., Li, C., Zhang, X., Wang, J., Zhang, G., Ling, L., & Lang, X. (2026). The association between triglyceride-glucose index and cognitive impairment in patients with first-episode drug-naïve schizophrenia: a large-scale cross-sectional study. BMC Psychiatry. https://doi.org/10.1186/s12888-026-08596-8

Image Credits: AI Generated

DOI: 10.1186/s12888-026-08596-8

Keywords: schizophrenia, triglyceride-glucose index, insulin resistance, cognitive impairment, first-episode psychosis, memory, attention, RBANS, metabolic health, drug-naïve patients, cross-sectional study, BMC Psychiatry