Causal atlas between inflammatory bowel disease and mental disorders: a bi-directional 2-sample Mendelian randomization study

Allergic diseases and T2DM: a bidirectional multivariable Mendelian randomization study and mediation analysis

BACKGROUND

Clinical studies involving observation have uncovered a mutual relationship between allergic disorders and diabetes, yet the precise causal link remains undetermined.

METHODS

We conducted two-sample bidirectional Mendelian randomization analyses using single nucleotide polymorphisms (SNPs) associated with allergic conditions (asthma, allergic rhinitis, atopic dermatitis) from genome-wide studies and SNPs related to type 2 diabetes from FinnGen. Initially, we evaluated the causal link between allergic disorders and type 2 diabetes through a univariate Mendelian randomization study, incorporating inverse variance weighting, MR-Egger, and the weighted median estimator. To address potential confounding, we employed multivariate Mendelian randomization. Finally, we validated mediators influencing the correlation between asthma and type 2 diabetes.

RESULTS

The Inverse variance weighted method showed that asthma genetically increased the risk of type 2 diabetes [Asthma-type 2 diabetes: β(95%CI)＝0.892 (0.152-1.632), p = 0.018]. Allergic rhinitis and type 2 diabetes exhibit a mutual protective effect: β(95% CI)＝-1.333 (-2.617 to -0.049), p = 0.042; type 2 diabetes-Allergic rhinitis: β(95%CI)＝-0.002 (-0.004 to -0.000), p = 0.018. The Multivariable Mendelian randomization study results showed that after excluding confounding factors, asthma still demonstrates statistical significance in relation to type 2 diabetes. Through mediation analysis, it was discovered that lung function and the percentage of monocytes in leukocytes exert an inhibitory effect on the mediation between asthma and type 2 diabetes.

CONCLUSION

The Multivariable Mendelian randomization study indicates asthma as a risk factor for type 2 diabetes. Lung function, and the percentage of monocytes in leukocytes, play an inhibitory role in asthma and type 2 diabetes mediating effects.

Causality between autoimmune diseases and schizophrenia: a bidirectional Mendelian randomization study

BACKGROUND

Observational studies have shown a link between autoimmune diseases and schizophrenia, with conflicting conclusions. Due to the existence of confounding factors, the causal link between autoimmune diseases and schizophrenia is still unknown.

METHOD

We conducted a comprehensive Mendelian randomization (MR) analysis of schizophrenia and ten common autoimmune diseases in individuals of European descent using genome-wide association studies (GWASs). To evaluate the relationships between autoimmune diseases and schizophrenia, inverse variance weighted, MR-RAPS, Bayesian weighted MR, constrained maximum likelihood, debiased IVW, MR-Egger, and weighted median were utilized. Several sensitivity analyses were performed to ensure the reliability of the study's results.

RESULTS

Our findings reveal that genetically predicted ankylosing spondylitis is related to an increased risk of schizophrenia, whereas celiac disease, type 1 diabetes, and systemic lupus erythematosus are associated with a lower risk of schizophrenia. In the reverse MR analysis, our study indicated that genetically predicted schizophrenia is linked to higher risks of ankylosing spondylitis, Crohn's disease, ulcerative colitis, inflammatory bowel disease, and psoriasis. Neither multiple sclerosis nor rheumatoid arthritis have been linked to schizophrenia, and vice versa.

CONCLUSION

Despite contradicting some other observational reports, this study showed support for a causal link between autoimmune diseases and schizophrenia. To gain a better understanding of the mechanisms underlying the development of immune-mediated schizophrenia, additional research is required to identify potential mechanisms identified in observational studies.

Unequal causality between autoimmune thyroiditis and inflammatory bowel disease: a Mendelian randomization study

Objective

This study aims to analyze the causal relationship between autoimmune thyroiditis (AIT) and inflammatory bowel disease (IBD) using bidirectional Mendelian randomization (MR).

Methods

Single nucleotide polymorphisms were obtained from FinnGen. Exposure-outcome causality was assessed using inverse variance weighted, MR-Egger, and weighted median. MR-Egger intercept, Cochran's Q, and leave-one-out sensitivity analysis were used to evaluate horizontal pleiotropy, heterogeneity, and robustness, respectively.

Results

Forward analysis revealed no significant association between AIT and the risk of ulcerative colitis (UC) (odds ratio [OR] 1.008, 95% confidence interval [CI] 0.986 to 1.03, p = 0.460) or Crohn's disease (CD) (OR 0.972, 95% CI 0.935 to 1.010, p = 0.143). Reverse analysis showed that UC (OR 0.961, 95% CI 0.783 to 1.180, p = 0.707) was not associated with AIT risk, while CD (OR 2.371, 95% CI 1.526 to 3.683, p < 0.001) was linked to an increased risk of AIT. Intercept analysis and Cochran's Q test indicated no horizontal pleiotropy or heterogeneity. Sensitivity analysis confirmed the robustness of the MR results.

Conclusion

This MR analysis suggests that CD, but not UC, is a risk factor for AIT, whereas AIT is not associated with the risk of IBD. Proactive prevention and treatment of CD can help mitigate the risk of AIT.

The Burden of Psychiatric Manifestations in Inflammatory Bowel Diseases: A Systematic Review With Meta-analysis

BACKGROUND

Psychiatric disorders in patients with inflammatory bowel disease (IBD) represent a significant but uncertain facet of the disease, with unsolved questions regarding their overall magnitude, their impact on intestinal disease, and the whole burden of psychiatric manifestations.

AIM

This systematic review summarizes the evidence on the prevalence and impact of psychiatric disorders, including depression, anxiety, bipolar disorder (BD), and schizophrenia, among patients with IBD.

METHODS

A systematic search across PubMed/MEDLINE, Embase, and Scopus databases from January 2010 to January 2023 was performed to identify relevant studies. The focus was on studies exploring the prevalence of specific psychiatric disorders in IBD patients compared to the general population and that reported specific outcome measures. A subsequent meta-analysis (MA) assessed the strength of the association between IBD and these psychiatric disorders, with data reliability ensured through rigorous extraction and quality assessment.

RESULTS

Out of 3,209 articles, 193 met the inclusion criteria and only 26 provided complete data for comprehensive analysis. These studies showed a significantly higher overall prevalence of psychiatric comorbidities in IBD patients compared to the general population. The MA showed a significant association between IBD and depression (pooled OR 1.42, 95% CI = 1.33-1.52, P < .0001) and anxiety (pooled OR 1.3, 95% CI = 1.22-1.44, P < .0001). The association between IBD and BD was significant (pooled OR 1.64, 95% CI = 1.20-2.24, P < .0001) but showed considerable heterogeneity (I2 = 94.01%). Only 3 studies examined the association between schizophrenia and IBD, providing widely heterogeneous results, with an inconclusive OR, estimated at 0.93 (95% CI = 0.62-1.39, P = .73).

CONCLUSIONS

This MA highlights the high prevalence of psychiatric disorders, particularly depression and anxiety, in IBD patients, which exceeds rates in the general population. BD in IBD is proving to be an important but under-researched area. The sparse and contradictory data on schizophrenia requires further investigation. These findings highlight the need for better understanding, early detection, and tailored mental health interventions in the management of IBD to significantly improve patients' quality of life.

Patterns of Immune Dysregulation in Bipolar Disorder

Background

Bipolar disorder is a debilitating mood disorder associated with a high risk of suicide and characterized by immune dysregulation. In this study, we used a multi-faceted approach to better distinguish the pattern of dysregulation of immune profiles in individuals with BD.

Methods

We analyzed peripheral blood mononuclear cells (bipolar disorder N=39, control N=30), serum cytokines (bipolar disorder N=86, control N=58), whole blood RNA (bipolar disorder N=25, control N=25), and whole blood DNA (bipolar disorder N=104, control N=66) to identify immune-related differences in participants diagnosed with bipolar disorder compared to controls.

Results

Flow cytometry revealed a higher proportion of monocytes in participants with bipolar disorder together with a lower proportion of T helper cells. Additionally, the levels of 18 cytokines were significantly elevated, while two were reduced in participants with bipolar disorder. Most of the cytokines altered in individuals with bipolar disorder were proinflammatory. Forty-nine genes were differentially expressed in our bipolar disorder cohort and further analyses uncovered several immune-related pathways altered in these individuals. Genetic analysis indicated variants associated with inflammatory bowel disease also influences bipolar disorder risk.

Discussion

Our findings indicate a significant immune component to bipolar disorder pathophysiology and genetic overlap with inflammatory bowel disease. This comprehensive study supports existing literature, whilst also highlighting novel immune targets altered in individuals with bipolar disorder. Specifically, multiple lines of evidence indicate differences in the peripheral representation of monocytes and T cells are hallmarks of bipolar disorder.

Shared genetic basis and causality between schizophrenia and inflammatory bowel disease: evidence from a comprehensive genetic analysis

BACKGROUND

The comorbidity between schizophrenia (SCZ) and inflammatory bowel disease (IBD) observed in epidemiological studies is partially attributed to genetic overlap, but the magnitude of shared genetic components and the causality relationship between them remains unclear.

METHODS

By leveraging large-scale genome-wide association study (GWAS) summary statistics for SCZ, IBD, ulcerative colitis (UC), and Crohn's disease (CD), we conducted a comprehensive genetic pleiotropic analysis to uncover shared loci, genes, or biological processes between SCZ and each of IBD, UC, and CD, independently. Univariable and multivariable Mendelian randomization (MR) analyses were applied to assess the causality across these two disorders.

RESULTS

SCZ genetically correlated with IBD (rg = 0.14, p = 3.65 × 10−9), UC (rg = 0.15, p = 4.88 × 10−8), and CD (rg = 0.12, p = 2.27 × 10−6), all surpassed the Bonferroni correction. Cross-trait meta-analysis identified 64, 52, and 66 significantly independent loci associated with SCZ and IBD, UC, and CD, respectively. Follow-up gene-based analysis found 11 novel pleiotropic genes (KAT5, RABEP1, ELP5, CSNK1G1, etc) in all joint phenotypes. Co-expression and pathway enrichment analysis illustrated those novel genes were mainly involved in core immune-related signal transduction and cerebral disorder-related pathways. In univariable MR, genetic predisposition to SCZ was associated with an increased risk of IBD (OR 1.11, 95% CI 1.07–1.15, p = 1.85 × 10−6). Multivariable MR indicated a causal effect of genetic liability to SCZ on IBD risk independent of Actinobacteria (OR 1.11, 95% CI 1.06–1.16, p = 1.34 × 10−6) or BMI (OR 1.11, 95% CI 1.04–1.18, p = 1.84 × 10−3).

CONCLUSIONS

We confirmed a shared genetic basis, pleiotropic loci/genes, and causal relationship between SCZ and IBD, providing novel insights into the biological mechanism and therapeutic targets underlying these two disorders.

Gut Microbiota and Gastrointestinal Symptoms in the Global Assessment of Obsessive-Compulsive Disorder: A Narrative Review of Current Evidence and Practical Implications

A growing body of literature suggests a link between bowel syndromes (e.g., irritable bowel syndrome and inflammatory bowel disease), gut microbiome alterations, and psychiatric disorders. This narrative review aims to explore the potential role of the gut microbiome in the pathogenesis and clinical presentation of obsessive-compulsive disorder (OCD) and to explore whether there is sufficient evidence to warrant considering gastrointestinal symptoms and their implication for the gut microbiome during the assessment and treatment of OCD. For this purpose, a PubMed search of studies focusing on OCD, gut microbiota, irritable bowel syndrome, and inflammatory bowel disease was conducted by two independent reviewers. While the current literature on gut microbiome and gastrointestinal issues in OCD remains limited, emerging evidence suggests gut microbiome alterations and high rates of bowel syndromes in this population. These findings emphasize the importance of incorporating comprehensive gastrointestinal assessments into the "global assessment of OCD". Such assessment should encompass various factors, including gastrointestinal physical comorbidities and symptoms, nutritional habits, bowel habits, fluid intake, exercise patterns, and potential microbiome dysfunctions and inflammation. Considering the treatment implications, interventions targeting gut health, such as probiotics and dietary modifications, may hold promise in improving symptoms in OCD patients with comorbid gastrointestinal problems. Further research in this area is warranted to better understand the interplay between gut health and OCD and to explore the effectiveness of targeted interventions in improving clinical outcomes.

A comprehensive Mendelian randomization study highlights the relationship between psychiatric disorders and non-tumor gastrointestinal diseases

Objective

Previous observational studies revealed the potential correlation between psychiatric disorders (PDs) and non-tumor gastrointestinal diseases (NTGDs). However, their causation remains unclear.

Methods

We explored the causal relationship between PDs and NTGDs through bidirectional two-sample Mendelian randomization (MR) study. Large-scale genome-wide association study (GWAS) summary statistics and bidirectional two-sample MR study were used to assess the causality between PDs and NTGDs. Multiple sensitivity analyses were used to identify the robustness of our results.

Results

We found that major depression was causally associated with increased risk of gastric ulcer (OR: 1.812, 95% CI: 1.320-2.487, p < 0.001) and irritable bowel syndrome (OR: 1.645, 95% CI: 1.291-2.097, p < 0.001). Meanwhile, genetically predicted gastroesophageal reflux disease contributed to the increased risk of anxiety disorders (OR: 1.425, 95% CI: 1.295-1.568, p < 0.001), and ulcerative colitis was related to increased risk of attention deficit/hyperactivity disorder (OR: 1.042, 95% CI: 1.008-1.078, p = 0.0157).

Conclusion

Our study provided MR evidence to support the close causality and identify the specific direction between eight PDs and eight common NTGDs. Experimental studies to further examine the causality, underlying mechanism, and therapeutic potential of PDs and NTGDs are required.

Inflammatory bowel disease and allergic diseases: A Mendelian randomization study

BACKGROUND

Inflammatory bowel disease (IBD) and allergic diseases possess similar genetic backgrounds and pathogenesis. Observational studies have shown a correlation, but the exact direction of cause and effect remains unclear. The aim of this Mendelian randomization (MR) study is to assess bidirectional causality between inflammatory bowel disease and allergic diseases.

METHOD

We comprehensively analyzed the causal relationship between inflammatory bowel disease (IBD), Crohn's disease (CD), ulcerative colitis (UC) and allergic disease (asthma, Hay fever, and eczema) as a whole, allergic conjunctivitis (AC), atopic dermatitis (AD), allergic asthma (AAS), and allergic rhinitis (AR) by performing a bidirectional Mendelian randomization study using summary-level data from genome-wide association studies. The analysis results mainly came from the random-effects model of inverse variance weighted (IVW-RE). In addition, multivariate Mendelian randomization (MVMR) analysis was conducted to adjust the effect of body mass index (BMI) on the instrumental variables.

RESULTS

The IVW-RE method revealed that IBD genetically increased the risk of allergic disease as a whole (OR = 1.03, 95% CI = 1.01-1.04, fdr.p = .015), AC (OR = 1.04, 95% CI = 1.01-1.06, fdr.p = .011), and AD (OR = 1.06, 95% CI = 1.02-1.09, fdr.p = .004). Subgroup analysis further confirmed that CD increased the risk of allergic disease as a whole (OR = 1.02, 95% CI = 1.00-1.03, fdr.p = .031), AC (OR = 1.03, 95% CI = 1.01-1.05, fdr.p = .012), AD (OR = 1.06, 95% CI = 1.02-1.09, fdr.p = 2E-05), AAS (OR = 1.05, 95% CI = 1.02-1.08, fdr.p = .002) and AR (OR = 1.03, 95% CI = 1.00-1.07, fdr.p = .025), UC increased the risk of AAS (OR = 1.02, 95% CI = 0.98-1.07, fdr.p = .038). MVMR results showed that after taking BMI as secondary exposure, the causal effects of IBD on AC, IBD on AD, CD on allergic disease as a whole, CD on AC, CD on AD, CD on AAS, and CD on AR were still statistically significant. No significant association was observed in the reverse MR analysis.

CONCLUSION

This Mendelian randomized study demonstrated that IBD is a risk factor for allergic diseases, which is largely attributed to its subtype CD increasing the risk of AC, AD, ASS, and AR. Further investigations are needed to explore the causal relationship between allergic diseases and IBD.

Global evolving patterns and cross-country inequalities of inflammatory bowel disease burden from 1990 to 2019: a worldwide report

AIMS

Inflammatory bowel disease (IBD) is a global disease. We aim to summarize the latest epidemiological patterns of IBD at the national, regional and global levels to give well-deserved attention and outline facilitating measures to reduce the disease burden.

METHODS

We collected the incidence, prevalence, mortality and disability-adjusted life years (DALYs) of IBD in 204 countries and territories from 1990 to 2019 using data from the Global Burden of Disease Study 2019. We further calculated the estimated annual percentage change (EAPC) to qualify the temporal trends of IBD burden by sex, age and region over the past 30 years.

RESULTS

Globally, a total of 404.55 thousand incident cases, 4898.56 thousand prevalent cases, 41.00 thousand deaths and 1622.50 thousand DALYs of IBD were estimated in 2019. The age-standardized DALYs decreased from 27.2 in 1990 to 20.15 per 100,000 people in 2019, with an EAPC of -1.04. The high socio-demographic index regions presented pronounced age-standardized rates (ASRs) consistently over the last 30 years. The high-income North America had the highest ASRs in 2019, followed by Western Europe and Australasia. No gender difference was observed after being stratified by sex.

CONCLUSIONS

The accumulated IBD patients are expected to increase in the future due to the increased rate of IBD in developing countries, and social aging in developed countries. Understanding the changes in epidemiological patterns helps to provide evidence to mitigate the rising burden of IBD.