Causal link between thyroid function and schizophrenia: a two-sample Mendelian randomization study

Risk of psychiatric disorders in patients with graves' disease: A nationwide population-based analysis

BACKGROUND

Graves' disease (GD) is an autoimmune hyperthyroidism and is associated with various psychiatric symptoms, such as irritability, mood changes, and insomnia. However, the epidemiological risk of psychiatric disorders among individuals with GD remains unclear. This study aimed to investigate whether a diagnosis of GD is associated with an increased incidence of various psychiatric disorders at a nationwide level.

METHODS

This study was a retrospective cohort study using data from the Korean National Health Insurance Claims database. We identified 20,851 patients with newly diagnosed GD and 46,008 age- and sex-matched controls. Cox proportional hazards models were used to estimate the risk of incident psychiatric disorders in patients with GD compared to controls. We further analyzed the hazard ratios (HRs) by follow-up period (<2 years, ≥2 years) since the diagnosis of GD.

RESULTS

Patients with GD exhibited a higher risk of developing psychiatric disorders compared to controls. The risk for incident depression (HR: 1.34, 95 % CI: 1.24-1.44), bipolar disorder (HR: 1.57, 95 % CI: 1.31-1.89), anxiety disorder (HR: 1.52, 95 % CI: 1.43-1.63), and sleep disorder (HR: 1.44, 95 % CI: 1.32-1.58) was significantly elevated. This increased risk for various psychiatric disorders, except schizophrenia, persisted even two years after the GD diagnosis. The association between GD and schizophrenia was not statistically significant.

CONCLUSIONS

This large-scale, population-based study demonstrates a significant association between GD and an increased risk of developing depression, bipolar disorder, anxiety disorder, and sleep disorder. The findings underscore the importance of long-term monitoring for psychiatric disorders in patients with GD.

Causal link between mental disorders and gastrointestinal diseases: a Mendelian randomization study

Background

Observational research suggests that mental diseases may increase the risk of gastrointestinal diseases. However, the causal link between these conditions remains unclear. In this study, we conducted a two-sample Mendelian randomization (MR) analysis to investigate the causal associations between common mental diseases and the risk of gastrointestinal diseases.

Methods

First, a series of parameters were set to select single-nucleotide polymorphisms (SNPs) from genome-wide association studies (GWAS). Second, A two-sample Mendelian randomization analysis was conducted to investigate the causal link between mental diseases (Alzheimer's disease, depression, major depressive disorder, Parkinson's disease, schizophrenia) and gastrointestinal diseases (gastritis and duodenitis, gastric cancer) while removing outliers using MR-PRESSO. Finally, eight methods of MR analysis were used to generate forest plots, including inverse variance weighted (IVW), inverse variance weighted (fixed effects) (IVW fixed effects), maximum likelihood (ML), MR-Egger, weighted median, penalized weighted median, simple mode, and weighted mode, with IVW considered the primary method.

Results

The result demonstrated that most MDs have no evidence of a causal link between gastrointestinal diseases except Parkinson's disease and gastric cancer based on the IVW method (OR = 0.929 [95% CI = 0.869-0.992], p = 0.029). Subsequently, we performed a robustness analysis to ensure consistency.

Conclusions

Our method provided evidence supporting a causal link between Parkinson's disease and the risk of gastric cancer. However, no evidence was found for other mental diseases influencing the risk of gastrointestinal diseases. Further research is warranted to explore how mental diseases affect the development of gastrointestinal diseases.

Neurological soft signs and thyroid hormones in schizophrenia spectrum disorders

BACKGROUND

Neurological soft signs (NSS) are minor sensory and motor deviations linked to neurodevelopmental disorders and schizophrenia spectrum disorders (SSD). Thyroid hormones (TH) are essential for neurodevelopment and are suggested to be altered in SSD. Yet, the relationship between NSS and TH is unclear.

OBJECTIVES

We evaluated the relationship between NSS and TH in individuals with SSD.

METHODS

We examined a total of 72 individuals with SSD. We assessed NSS using the Neurological Evaluation Scale (NES) and clinical symptoms using the Positive and Negative Syndrome Scale (PANSS). We collected fasting blood samples to measure serum levels of thyroid-stimulating hormone (TSH), free thyroxine (fT4), and free triiodothyronine (fT3). We used the t-test to compare differences between sex and the Pearson correlation to test for correlations between NSS, TH and psychopathology separately for males and females.

RESULTS

We observed a negative correlation between fT4 and NES total score (r = -0.374, p = .032), and NES subdomain "sensory integration" (r = -0.372, p = .033). The correlation between fT4 and "sensory integration" remained largely unchanged when controlling for age, DOI, and antipsychotic dose in OLZ equivalents by performing partial correlation analyses (r = -0.424, p = .049). Serum fT3 and TSH levels exhibited no significant correlation with NES scores but the PANSS negative symptoms score was negatively associated with fT3 (r = -0.472, p < .001).

CONCLUSIONS

Lower fT4 levels were associated with NSS severity and specific NSS subdomains only in male individuals. In the overall sample, we detected a significant negative correlation between fT3 and negative symptoms. Future studies should examine a larger sample of drug-naïve individuals with SSDs, followed-up longitudinally in time to infer causality.

Casual effect of ulcerative colitis on chronic heart failure: results from a bidirectional Mendelian randomization study

This study aimed to detect the causal effect of ulcerative colitis (UC) on heart failure. A bidirectional two-sample Mendelian randomization (MR) analysis was performed. The causal impact of UC on heart failure was determined via MR by performing a genome-wide association study in which 4 UCs descending from European ancestors were set as individual exposures. The inverse-variance weighted (IVW) method was used as the main method, and 4 other methods were set as assistant parameters. Susbequently, the MR results were combined with meta-analysis results. The MR Egger method was employed to investigate pleiotropy. The leave-one-out method was utilized for sensitivity analysis. Furthermore, a reverse-directional study was conducted. There was evidence of the causal effect of UC on heart failure in MR estimates using 4 UC datasets. The IVW method revealed that the odds ratio (OR) = 1.03, 95% confidence interval (CI) = 1.01-1.06, P = 0.0441 when the first UC dataset was used; OR = 1.03, 95% CI = 1.01-1.05, P = 0.0445 when the second UC dataset was used; OR = 2046, 95% CI = 1.37-3.05E + 06, P = 0.0409 when the third UC dataset was used; and OR = 8.12E + 04, 95% CI = 29.09-2.27E + 08, P = 0.0052 when the fourth UC dataset was used. A meta-analysis of 4 MR studies revealed that UC had a statistically significant causal effect on heart failure (OR = 1.03, 95% CI = 1.01-1.05; P = 0.0074). Reverse MR analysis revealed that heart failure did not have a causal effect on UC. There was no pleiotropy. This MR study demonstrated that UC had a causal effect on heart failure and that there was no reverse causal effect.

Sex-specific differences in the relationship between thyroid hormones and neurocognition in schizophrenia: A large-scale cross-sectional study

BACKGROUND

Sex differences in thyroid hormones, cognitive function, and psychiatric symptoms in schizophrenia remain underexplored. The study aimed to investigate the cross-sectional relationships between thyroid hormone levels, cognitive impairments, and clinical symptoms in people with chronic schizophrenia, with a focus on sex differences.

METHODS

We included 1007 people with schizophrenia (602 males and 405 females), and 326 healthy controls (193 males and 133 females). Cognitive function and psychiatric symptoms were assessed using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and the Positive and Negative Syndrome Scale (PANSS), respectively. Blood samples were collected to measure serum total thyroxine (TT4), total triiodothyronine (TT3), thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3). Analysis of variance (ANOVA) and two-way ANOVA were used to compare clinical characteristics and sex differences. Pearson correlation and hierarchical linear regression were conducted to assess the relationships between thyroid hormone levels, cognitive impairments, and clinical symptoms.

RESULTS

People with schizophrenia exhibited lower levels of thyroid hormones compared to the healthy control group (both P < 0.01). Male patients had higher TT3 and FT3 levels than female patients (both P < 0.01). The cognitive scores of the healthy controls were generally higher than those of people with schizophrenia (P < 0.001). Additionally, there were significant sex differences in visuospatial/constructive abilities and language (both P < 0.01) among people with schizophrenia, with males scoring higher than females. The linear regression found that in the cognitive domain, TT4 was negatively associated with Visuospatial/Constructive abilities and RBANS total scores in male patients (both P < 0.05), whereas TT4 was positively associated with these abilities and attention in female patients (all P < 0.05). Additionally, in male patients, TT3 was negatively associated with most of PANSS scale (all P < 0.05). In female, TT3 was only negatively associated with the PANSS Negative scale (P < 0.05).

CONCLUSION

Sex differences exist in thyroid hormone T3 levels in people with schizophrenia. The association between thyroid hormones and cognitive performance varies by sex in chronic schizophrenia.

Correlation analyse between thyroid hormone levels and severity of schizophrenia symptoms

BACKGROUND

The imbalance of hormone levels in the body is closely related to the occurrence and progression of schizophrenia, especially thyroid hormones.

AIM

To study the relationship between triiodothyronine (T3), thyroxine (T4), free T3 (FT3), free T4 (FT4), thyroid stimulating hormone (TSH) and schizophrenia.

METHODS

In this study, 100 schizophrenia patients were selected from our hospital between April 2022 and April 2024. Their clinical data were analyzed retrospectively. Based on the Positive and Negative Syndrome Scale (PANSS) score, patients were divided into mild (1-3 points, n = 39), moderate (4 points, n = 45), and severe groups (5-7 points, n = 16). Additionally, 55 healthy individuals served as a control group. Venous blood samples were collected to measure T3, T4, FT3, FT4, TSH, and cortisol concentrations, analyzing their relationship with PANSS scores.

RESULTS

The serum levels of T3, FT3, FT4, TSH and cortisol in the schizophrenia group were lower than those in the control group (P < 0.05). With the increase of the severity of the disease, the concentrations of T3 and T4 decreased, while the concentrations of TSH and cortisol increased (P < 0.05). The concentrations of TSH and cortisol were positively correlated with the PANSS score, while T3 and T4 were negatively correlated with the PANSS score (P < 0.05). The receiver operating characteristic curve results showed that T3, T4, TSH, and cortisol had good efficacy in the diagnosis of schizophrenia. Logistic results showed that decreased T3 level, decreased T4 level, decreased TSH level and increased cortisol level may be independent risk factors for schizophrenia.

CONCLUSION

Thyroid hormone levels are associated with the severity of schizophrenia symptoms, which can provide new solutions for the diagnosis and treatment of schizophrenia.

Application of Mendelian randomization in thyroid diseases: a review

Thyroid diseases are increasingly prevalent, posing significant challenges to patients' quality of life and placing substantial financial burdens on families and society. Despite these impacts, the underlying pathophysiology of many thyroid conditions remains poorly understood, complicating efforts in treatment, management, and prevention. Observational studies can identify associations between exposure variables and disease; however, they often struggle to account for confounding factors and reverse causation. Understanding disease occurrence, epidemiological trends, and clinical diagnosis, prevention, and treatment relies heavily on robust etiological research. Mendelian randomization, a method grounded in genetics and epidemiology, has been widely employed in studying the etiology of thyroid diseases, offering a solution to some of these challenges. This paper categorizes thyroid diseases into thyroid dysfunction and thyroid cancer, reviewing related Mendelian randomization studies. It further provides novel perspectives and approaches for investigating the mechanisms underlying thyroid diseases and designing intervention strategies.

Causal associations between severe COVID-19 and diseases of seven organs: a proteome-wide mendelian randomization study

The coronavirus disease 2019 (COVID-19) pandemic poses an enormous threat to public health worldwide. Many retrospective studies and case reports to date have shown associations between severe COVID-19 and diseases of multi-organs. However, the research on the causal mechanisms behind this phenomenon is neither extensive nor comprehensive. We conducted a proteome-wide Mendelian randomization (MR) study using summary statistics from a Genome-Wide Association Studies (GWAS) of severe COVID-19 and diseases related to seven organs: lung, spleen, liver, heart, kidney, testis, and thyroid, based on the European ancestry. The primary analytical method used is the radial inverse variance-weighted (radial IVW) method, supplemented with the inverse variance-weighted (IVW), weighted-median (WM), MR-Egger methods. Our findings have confirmed the association between severe COVID-19 and multiple organ-related diseases, such as Hypothyroidism, strict autoimmune (HTCBSA), Thyroid disorders (TD), and Graves' disease (GD). And we have also identified certain proteins that are associated with organ-related diseases, such as Superoxide Dismutase 2 (SOD2) and TEK Receptor Tyrosine Kinase (TEK), which are also considered potential drug targets. Phenotype scanning and sensitivity analyses were implemented to consolidate the results for Mendelian randomization. This study provides a compelling foundation for investigating COVID-19 caused diseases in future studies.

Causal relationships of mental diseases and thyroid diseases based on a Mendelian randomization study

Evidence from observational researches have suggested that mental diseases are able to affect thyroid diseases. However, the causal relationship between mental diseases and the risk of thyroid diseases still remains unclear. Herein, we conducted a two-sample Mendelian randomization (MR) statistical analysis method to assess the causality between mental diseases and thyroid diseases. Initially, publicly available genome-wide association studies summary data were leveraged to obtain single-nucleotide polymorphisms based on set parameters. Subsequently, a two-sample MR was utilized to analyze causal relationships between mental diseases (Alzheimer disease, bipolar disorder, major depressive disorder, Parkinson disease, schizophrenia) and thyroid diseases (hyperthyroidism/thyrotoxicosis, hypothyroidism) with removing outliers based on MR-PRESSO method. Finally, 8 regression MR methods (inverse variance weighted [IVW], IVW fixed effects, c, MR Egger, weighted median, penalized weighted median, simple mode, weighted mode) were performed to evaluate bias and effectiveness, of which IVW was considered as the primary method. Our results demonstrated that most of mental diseases have no causal relationships with thyroid diseases except bipolar disorder and hyperthyroidism/thyrotoxicosis based on IVW method [odds ratio: 0.999, 95% confidence interval: 0.998-1.000, P = .028], and bipolar disorder and hypothyroidism based on IVW method [odds ratio: 0.997, 95% confidence interval: 0.995-0.999, P = .002]. Then we subsequently conducted a consistent robustness analysis to assess heterogeneity and horizontal pleiotropy. Our method reports causal relationships exist mental diseases and the risk of thyroid diseases. Subsequent researches are still warranted to determine how mental diseases influence the development of thyroid diseases.

Causal relationships between gut microbrome and digestive system diseases: A two-sample Mendelian randomization study

Growing evidences of recent studies have shown that gut microbrome are causally related to digestive system diseases (DSDs). However, causal relationships between the gut microbiota and the risk of DSDs still remain unclear. We utilized identified gut microbiota based on class, family, genus, order and phylum information and digestive system diseases genome-wide association study (GWAS) dataset for two-sample Mendelian randomization (MR) analysis. The inverse variance weighted (IVW) method was used to evaluate causal relationships between gut microbiota and 7 DSDs, including chronic gastritis, colorectal cancer, Crohn's disease, gastric cancer, gastric ulcer, irritable bowel syndrome and esophageal cancer. Finally, we verified the robustness of MR results based on heterogeneity and pleiotropy analysis. We discovered 15 causal associations with genetic liabilities in the gut microbiota and DSDs, such as genus Victivallis, genus RuminococcaceaeUCG005, genus Ruminococcusgauvreauiigroup, genus Oxalobacter and so on. Our MR analysis revealed that the gut microbiota is causally associated with DSDs. Further researches of the gut microbiota and the pathogenesis of DSDs are still significant and provide new methods for the prevention and treatment of DSDs.

Asparagine reduces the risk of schizophrenia: a bidirectional two-sample mendelian randomization study of aspartate, asparagine and schizophrenia

BACKGROUND

Despite ongoing research, the underlying causes of schizophrenia remain unclear. Aspartate and asparagine, essential amino acids, have been linked to schizophrenia in recent studies, but their causal relationship is still unclear. This study used a bidirectional two-sample Mendelian randomization (MR) method to explore the causal relationship between aspartate and asparagine with schizophrenia.

METHODS

This study employed summary data from genome-wide association studies (GWAS) conducted on European populations to examine the correlation between aspartate and asparagine with schizophrenia. In order to investigate the causal effects of aspartate and asparagine on schizophrenia, this study conducted a two-sample bidirectional MR analysis using genetic factors as instrumental variables.

RESULTS

No causal relationship was found between aspartate and schizophrenia, with an odds ratio (OR) of 1.221 (95%CI: 0.483-3.088, P-value = 0.674). Reverse MR analysis also indicated that no causal effects were found between schizophrenia and aspartate, with an OR of 0.999 (95%CI: 0.987-1.010, P-value = 0.841). There is a negative causal relationship between asparagine and schizophrenia, with an OR of 0.485 (95%CI: 0.262-0.900, P-value = 0.020). Reverse MR analysis indicates that there is no causal effect between schizophrenia and asparagine, with an OR of 1.005(95%CI: 0.999-1.011, P-value = 0.132).

CONCLUSION

This study suggests that there may be a potential risk reduction for schizophrenia with increased levels of asparagine, while also indicating the absence of a causal link between elevated or diminished levels of asparagine in individuals diagnosed with schizophrenia. There is no potential causal relationship between aspartate and schizophrenia, whether prospective or reverse MR. However, it is important to note that these associations necessitate additional research for further validation.