The clinical observation that first drew attention to calcium in schizophrenia is deceptively simple. Hypocalcemia, a lowered concentration of calcium in the blood, has been consistently reported in patients with the disorder, yet clinicians have long treated it as a sequela rather than a causal determinant. A large cohort analysis did associate hypocalcemia with use of the atypical antipsychotic risperidone, and antipsychotics are known to modulate the immune system and bone metabolism, producing secondary metabolic effects that are well documented in this population. Recent interpretations of akathisia, the distressing syndrome of inner restlessness and objective fidgeting, rocking and pacing that can accompany antipsychotic therapy, also implicate the calcium channel blockade that these drugs perform. Evidence from a Mendelian randomization study adds a genetic dimension, suggesting that calcium regulatory hormones are linked to psychiatric phenotypes and that innate differences in calcium regulation could influence both disease biology and individual sensitivity to drug-induced movement disorders.

Calcium channels themselves have a strong neuropsychiatric pedigree. Mutations and polymorphisms in these channels have been associated with the onset of migraine, cerebellar ataxia, autism, depression, bipolar disorder and schizophrenia. Because calcium entry through voltage-gated channels depolarizes the cell surface membrane and triggers gene expression, secretion and contraction in neuronal cells, any inherited or acquired disturbance of channel function has the potential to reshape synaptic plasticity across the brain. The authors emphasize that a host of vulnerability factors, including unhealthy lifestyle, reduced physical activity, smoking, poor diet and genetic elements, confer risk for schizophrenia, and that a substantial number of patients are predisposed to the cumulative side effects of their medications. All of these factors converge on systemic changes, especially along immune and metabolic trajectories.

The genuinely new perspective comes from the immune side. The research group previously demonstrated elevated levels of soluble Suppressor of Tumorigenicity-2, or sST2, a member of the interleukin-1 family, during the exacerbation of psychosis. When sST2 binds IL-33, it dampens the effects of that alarmin cytokine, and in schizophrenia sST2 was found to exert beneficial effects by negatively correlating with scores reflecting negative symptoms. In a subsequent study of 27 patients with schizophrenia in remission, the team observed something unexpected: a statistically significant positive correlation between serum sST2 concentrations and calcium levels, with a correlation coefficient of 0.454 and a p value of 0.020. These findings suggest a connection between calcium and a key substrate of sterile inflammation in the disorder, positioning calcium as a potential regulator of immune-metabolic signaling rather than a passive bystander.

To understand why this correlation matters, one must follow calcium into the endoplasmic reticulum, the intracellular store that fine-tunes signaling in neurons and pancreatic beta cells alike. A review by Luiz Bergantin provided critical insights into the functional implications of dysregulated intracellular calcium released from the endoplasmic reticulum, unfolding the basis of cyclic adenosine monophosphate stimulation in schizophrenia, asthma and diabetes. Under this framework, increased intracellular calcium concentration may precede dysregulation of the dopamine system, airway smooth muscle hypercontractility and decreased insulin release. In other words, a single intracellular disturbance could set the stage for the dopaminergic dysfunction of psychosis, the bronchial hypercontractility of asthma and the insulin secretory failure of diabetes simultaneously.

The molecular bridge between these processes is the protein Disrupted-In-Schizophrenia 1, or DISC1, one of the most significant susceptibility genes for the disorder. DISC1 is localized to the endoplasmic reticulum membrane and functionally interacts with components that regulate calcium release. Loss of DISC1 function leads to dysregulation of calcium handling, with increased release of the ion into the cytosol. Based on these findings, DISC1 acts as a fine-tuning regulator of calcium release from the endoplasmic reticulum and of intracellular calcium dynamics, while its dysfunction produces significant disruption of intracellular signaling. These disturbances are accompanied by disruption of synaptic homeostasis and of dopaminergic and glutamatergic neurotransmission, which are central characteristics of schizophrenia. Mutations in DISC1 have been shown to alter the functioning of IP3 receptors and voltage-gated calcium channels, directly implicating endoplasmic reticulum calcium dynamics in major mental illness.

Pancreatic beta cells tell a parallel story. Under conditions of chronic hyperinsulinemia and endoplasmic reticulum stress, the synthesis of proinsulin and the organelle’s regulatory role in maintaining intracellular calcium homeostasis are disrupted, accompanied by increased calcium leakage from the endoplasmic reticulum and a resulting chronic rise in cytosolic calcium. This imbalance may begin with enhanced insulin secretion, but over time it depletes secretory capacity and drives functional decompensation of the beta cells. Chronically elevated cytosolic calcium activates calcium-dependent proteases, mitochondrial pathways and oxidative stress, leading to apoptotic mechanisms and loss of beta-cell mass. Chronic low-grade inflammation through secreted cytokines further enhances endoplasmic reticulum stress and destabilizes calcium homeostasis, creating a vicious cycle in which immune signaling and calcium handling destroy each other’s equilibrium.

The IL-33/ST2 pathway weaves the immune and metabolic threads together. Under physiological conditions, IL-33 activates regulatory T cells and type 2 innate lymphoid cells, promoting an anti-inflammatory milieu and adipose thermogenesis. In obesity, however, an expression-function paradox emerges: although IL-33 expression is elevated in obese adipose tissue, effector cell dysfunction impairs its protective attributes, including sST2-mediated neutralization. The authors also draw parallels between the immune responses of asthma, the prototype of a type 2 immune response, and schizophrenia, noting that patients with the psychiatric disorder appear to have a more pronounced type 2 immune response, as indicated by elevated sST2 during exacerbations, a response that may be corrected with antipsychotics. Repeated exacerbations in both diseases, accompanied by inflammation in the microvascular network, could lead to deterioration of joint tissues, fibrosis and gliosis. Consistent with this, one etiological model of asthma proposed calcium elevation within the endoplasmic reticulum as an endogenous inducer of inflammation, and in vitro studies observed that ST2 was less expressed in bronchial epithelial cells in asthma, with stimulation by IL-33 increasing intracellular calcium in that proinflammatory environment.

The clinical implications are considerable. A meta-review of first-episode psychosis has framed the condition as a multisystem disorder, with central nervous system, immune, cardiometabolic and endocrine alterations present from the outset, and the authors suggest that calcium is involved not only in early programming but in the orchestration of a unique immunometabolic and mental profile later in life. Cumulative effects could drive neurodegeneration and neuroprogression in patients, and frequent exacerbations and deterioration may be linked to disturbances in calcium/ST2 dynamics. Inflammation and calcium homeostasis are among the hallmarks of aging pathways used to identify potential frailty biomarkers. A considerable number of patients with schizophrenia have chronic low-grade inflammation and constitute an inflammatory subgroup of the disorder, with notable immune differences observed in those resistant to conventional therapy. Immune markers are increasingly suggested as potential targets of pharmacotherapy, and the IL-33/ST2 signaling pathway is emerging as a viable new target across neuroinflammatory conditions, since targeting sST2 could attenuate neuroinflammation and promote repair mechanisms in the brain.

Novel antipsychotic drugs are already moving in this direction. The Trace Amine-Associated Receptor 1 agonist has been demonstrated to reduce microglia-mediated inflammatory response, acts as an inhibitory modulator of the dopaminergic system, and is considered a promising new target for improving beta-cell health in type 2 diabetes. Notably, TAAR1 impacts the signaling and internal mobilization of calcium, and the authors argue that the crosstalk among TAAR1, calcium and the IL-33/ST2 pathway needs further exploration in schizophrenia. Improvement of the negative and cognitive symptoms with more viable anti-inflammatory or immunomodulatory agents should be the main focus of future pharmacotherapeutic strategies. The authors close with a call to incorporate these findings rapidly into clinical practice: a better understanding of calcium-dependent immune-metabolic signaling may improve the identification of biologically distinct schizophrenia phenotypes and of patients at increased risk of metabolic comorbidity, and future studies should determine whether calcium/ST2 interactions could serve as clinically relevant biomarkers or therapeutic targets. If the hypothesis holds, the ion that fires every synapse may also explain why the mind and the metabolism fail together.

Subject of Research: Calcium at the crossroads of the immunometabolic signaling and comorbidity in schizophrenia

Article Title: Calcium at the crossroads of the immunometabolic signaling and comorbidity in schizophrenia

Article References: Calcium at the crossroads of the immunometabolic signaling and comorbidity in schizophrenia. (n.d.). https://doi.org/10.3389/fnsyn.2026.1882307

Image Credits: AI Generated

DOI: 10.3389/fnsyn.2026.1882307

Keywords: calcium signaling, schizophrenia, sST2, IL-33/ST2 pathway, DISC1, immunometabolism, Calcium, crossroads, immunometabolic, signaling, comorbidity, scientific research

The findings matter because schizophrenia has long been viewed primarily through the lens of dopamine signaling and abnormal brain development. Yet a growing body of evidence implicates chronic low-grade inflammation as a contributing factor, and immune signaling pathways have emerged as promising targets for understanding — and perhaps eventually treating — aspects of the illness that antipsychotic medications leave untouched. The IL-33/sST2 axis sits at a particularly interesting junction within that landscape, because it connects immune alarm signaling directly to both neural tissue and metabolic regulation.

IL-33 itself is a fascinating molecule. Often described as an “alarmin,” it is normally stored inside the nuclei of endothelial cells, epithelial cells and other structural tissues, and it is released when cells are damaged or stressed. Once outside the cell, IL-33 acts as a damage-associated molecular pattern — a DAMP in immunological shorthand — alerting the immune system to tissue injury. It exerts its effects by binding to a receptor called suppression of tumorigenicity-2, or ST2, which sits on the surface of immune cells, mast cells, and even neurons and glia. The brain is richly endowed with IL-33 and ST2 expression, particularly in astrocytes and microglia, the resident immune cells of the central nervous system, which has fueled speculation that dysregulated IL-33 signaling could contribute to the neuroinflammatory component of psychiatric disease.

There is a twist in the receptor biology that makes measuring this system tricky. The ST2 gene produces two major isoforms: a membrane-bound form that transmits signals into the cell, and a soluble decoy form, sST2, that floats freely in the blood and mops up IL-33 before it can bind its functional receptor. In other words, sST2 acts as a natural brake on IL-33 activity. When researchers measure both molecules in serum, the ratio between them offers a rough gauge of the balance between immune alarm signaling and its suppression. The new study examined exactly this balance in 39 patients with schizophrenia, 24 of their healthy siblings, and 25 unrelated healthy controls — a design that allows investigators to ask whether immune alterations are tied to the illness itself or to shared genetic and familial vulnerability.

Serum concentrations of IL-33 and sST2 were quantified using enzyme-linked immunosorbent assay, the workhorse technique of protein biomarker research, alongside a battery of metabolic measurements including waist circumference, blood pressure, fasting glucose, and lipid profiles. Cognitive performance was assessed using well-validated neuropsychological instruments, notably the Trail Making Test, which probes executive function and processing speed, while social and occupational functioning was rated with the Personal and Social Performance Scale. Symptom severity was measured with the Positive and Negative Syndrome Scale, and metabolic syndrome was defined by standard clinical criteria.

The headline result is a clear immune signature: patients with schizophrenia showed elevated IL-33 and reduced sST2 relative to healthy controls, a pattern consistent with heightened and insufficiently counteracted alarmin signaling. Intriguingly, the healthy siblings of patients — who share roughly half their genes with their ill relatives but do not have the diagnosis — showed IL-33 levels similar to controls rather than to patients. That pattern suggests the IL-33 elevation may be more closely tied to the illness state or its treatment than to inherited familial risk alone, though the authors are careful to note that the sibling subgroup was small and the result should be interpreted with caution. sST2 levels in siblings did not differ significantly from either the patient or control groups.

When the team explored how these immune markers relate to the clinical realities of schizophrenia, the picture became more nuanced. The IL-33/sST2 axis was associated with metabolic syndrome, the dangerous cluster of abdominal obesity, hypertension, dyslipidemia and insulin resistance that affects a large proportion of people with schizophrenia and dramatically shortens their life expectancy through cardiovascular disease. The markers also correlated with social functioning, the capacity to maintain relationships, work, and independent daily life that most strongly predicts long-term quality of life in this population. But when it came to the cognitive domain, the story changed: neither IL-33, nor sST2, nor their ratio showed significant correlations with executive function or processing speed, and metabolic parameters likewise showed no association with neurocognitive test performance.

This dissociation is scientifically telling. Cognitive impairments in schizophrenia are considered core features of the illness, tightly linked to neurodevelopment, and often present before the onset of psychosis. If the IL-33/sST2 axis tracks metabolic and functional outcomes but not cognition, it may be marking a distinct pathological pathway — one involving peripheral inflammation and metabolic dysregulation — rather than the neurodevelopmental processes that drive cognitive deficits. That distinction could matter enormously for future therapeutic strategies. Anti-inflammatory or immunomodulatory interventions might, for example, improve metabolic health and social outcomes in schizophrenia without being expected to rescue cognitive performance, and biomarkers like sST2 could eventually help identify which patients would benefit most.

The researchers also used receiver operating characteristic analysis to explore whether IL-33 or sST2 could serve as diagnostic cut-offs capable of distinguishing patients from controls. While the analysis yielded cut-off values with measurable discriminatory power, the authors are explicit that these findings do not support clinical use. The study is cross-sectional, meaning it captures a single moment in time and cannot establish whether immune changes precede or follow the illness and its treatments. The sample is small, particularly the sibling group, and the authors acknowledge in their conclusions that the exploratory nature of the work, the limited cohort size, and the absence of longitudinal data mean IL-33 and sST2 cannot yet be considered diagnostic or prognostic biomarkers for schizophrenia.

Those caveats are standard scientific humility, but they do not erase the study’s contribution. Replicated elevations of IL-33 with compensatory failure of its soluble decoy receptor would strengthen the case that alarmin signaling is a genuine player in schizophrenia biology, connecting the immune system, adipose tissue, and the social difficulties that define real-world disability in the disorder. Larger prospective cohorts, ideally following patients from illness onset and including first-episode and drug-naive participants to disentangle medication effects, are the necessary next step. For now, the study adds an intriguing new thread to the growing tapestry of psycho-immunology: the alarm signals of a stressed immune system may echo far beyond inflammation, shaping metabolism and the fabric of social life in people living with schizophrenia.

Subject of Research: The association of serum IL-33 and sST2 immune markers with metabolic syndrome, social functioning, and cognition in schizophrenia.

Article Title: IL-33/sST2 axis is associated with metabolic syndrome and social functioning, but not executive function or processing speed, in schizophrenia

Article References: IL-33/sST2 axis is associated with metabolic syndrome and social functioning, but not executive function or processing speed, in schizophrenia. (n.d.). https://doi.org/10.1186/s12888-026-08414-1

Image Credits: AI Generated

DOI: 10.1186/s12888-026-08414-1

Keywords: schizophrenia, IL-33, sST2, inflammation, biomarkers, metabolic syndrome, social functioning, executive function, processing speed, immune system, psychiatry, alarmins