Psychiatric disorders and Type 2 diabetes mellitus: A bidirectional Mendelian randomization

Psychosocial Problems at Preschool Age and Cardiometabolic Health Profile at Preadolescence

OBJECTIVE

Evidence suggests that children with psychosocial problems face a higher risk of cardiometabolic diseases in adulthood. However, this may already be evident prior to adulthood. In this study, the associations between psychosocial problems at preschool age and cardiometabolic outcomes 6 years later were investigated.

METHODS

Data from 936 participants from the Amsterdam Born Children and their Development (ABCD) study was used. Psychosocial problems were assessed using the Strengths & Difficulties Questionnaire (SDQ) when the children were 5-6 years old, reported by both mothers and teachers. Cardiometabolic parameters, including body mass index, waist circumference, total cholesterol, triglycerides, high- and low-density lipoprotein cholesterol, fasting glucose, systolic and diastolic blood pressure, and carotid intima-media thickness were subsequently measured at ages 11-12 years. The associations between psychosocial problems and cardiometabolic outcomes were assessed using multivariable linear and logistic regression models.

RESULTS

In model 1, adjusted for age, sex, and puberty status, and in model 2, for sociodemographic and biological predisposition factors, the combined mother-teacher score yielded a positive association with clustered cardiometabolic score (b = 0.05, 95% confidence interval = 0.03-0.10) 6 years later. Adjusting for lifestyle factors rendered this association nonsignificant. Significant associations between mother-reported SDQ scores and most cardiometabolic parameters, except for triglycerides, diminished after controlling for confounders. Children with higher total SDQ score (by mother) had 1.31 times higher odds of developing metabolic syndrome (95% confidence interval = 1.05-1.62).

CONCLUSION

This study established a small inverse association between mother-reported psychosocial problems at ages 5-6 years and cardiometabolic health profile at ages 11-12 years.

Phenome-wide investigation of bidirectional causal relationships between major depressive disorder and common human diseases

The high comorbidity of major depressive disorder (MDD) with other diseases has been well-documented. However, the pairwise causal connections for MDD comorbid networks are poorly characterized. We performed Phenome-wide Mendelian randomization (MR) analyses to explore bidirectional causal associations between MDD (N = 807,553) and 877 common diseases from FinnGen datasets (N = 377,277). The inverse variance weighting method was the primary technique, and other methods (weighted median and MR-Egger) were used for sensitivity analyses. Our MR analyses showed that the genetic liability to MDD is causally associated with the risks of 324 disease phenotypes (average b: 0.339), including 46 psychiatric and behavioral disorders (average b: 0.618), 18 neurological diseases (average b: 0.348), 44 respiratory diseases (average b: 0.345), 40 digestive diseases (average b: 0.281), 18 circulatory diseases (average b: 0.237), 37 genitourinary diseases (average b: 0.271), 66 musculoskeletal and connective diseases (average b: 0.326), 22 endocrine diseases (average b: 0.302), and others. In a reverse analysis, a total of 51 genetic components predisposing to various diseases were causally associated with MDD risk (average b: 0.086), including 5 infectious diseases (average b: 0.056), 11 neurological diseases (average b: 0.106), 14 oncological diseases (average b: 0.108), and 5 psychiatric and behavioral disorders (average b: 0.114). Bidirectional causal associations were identified between MDD and 15 diseases. For most MR analyses, little evidence of heterogeneity and pleiotropy was detected. Our findings confirmed the extensive and significant causal role of genetic predisposition to MDD in contributing to human disease phenotypes, which were more pronounced than those seen in the reverse analysis of the causal influences of other diseases on MDD.

Genetic association of type 2 diabetes mellitus and glycaemic factors with primary tumours of the central nervous system

Type 2 diabetes mellitus (T2DM) is a pivotal chronic disease with an increasing prevalence. Recent studies have found associations between T2DM and the development of central nervous system (CNS) tumours, a special class of solid tumours with an unclear pathogenesis. In this study, we aimed to explore the relationship between T2DM and certain glycaemic factors with common CNS tumours by using genetic data to conduct Mendelian randomization (MR) and co-localisation analysis. We found a causal relationship between T2DM and glioblastoma, fasting glucose and spinal cord tumours, glycated haemoglobin and spinal cord tumours, and insulin-like growth factor-1 and spinal cord tumours, pituitary tumours, and craniopharyngiomas. These results clarify the relationship between T2DM, glucose-related factors, and common CNS tumours, and they provide valuable insight into further clinical and basic research on CNS tumours, as well as new ideas for their diagnosis and treatment.

Mitochondrial related Mendelian randomization identifies causal associations between metabolic disorders and childhood neurodevelopmental disorders

Childhood neurodevelopmental disorders (NDDs), including autism spectrum disorder (ASD), attention-deficit hyperactivity disorder, and Tourette syndrome, are a predominant cause of health-related disabilities in children and adolescents. Nevertheless, disease biomarkers are still limited. The aim of this study was to evaluate the potential, causal relationship between mitochondrial DNA copy number (mtDNA-CN), metabolic disorders, and childhood NDDs using the two-sample Mendelian randomization (MR) method. Genetic associations with mtDNA-CN, disorders of lipoprotein metabolism, and disorders of iron metabolism were selected as exposures, and genome-wide association data from ASD, attention-deficit hyperactivity disorder, and Tourette syndrome were utilized as outcomes. Results of the study suggested that a high degree of disordered lipoprotein metabolism related increases in ASD risk result from a decrease in mtDNA-CN (disordered lipoprotein metabolism-mtDNA: inverse variance weighting β: -0.03, 95% confidence interval: -0.05 to -0.02, P = 2.08 × 10-5; mtDNA-CN-ASD: inverse variance weighting odds ratio: 0.83, 95% confidence interval: 0.69-0.99, P = .034). The research findings implied that mtDNA-CN can mediate disorders of lipoprotein metabolism, potentially influencing the development of ASD. The potential impact of the results of this study for the prevention and treatment of childhood NDDs warrants validation in robust randomized clinical trials.

Causality between diabetes and membranous nephropathy: Mendelian randomization

BACKGROUND

Membranous nephropathy (MN) has not yet been fully elucidated regarding its relationship with Type I and II Diabetes. This study aims to evaluate the causal effect of multiple types of diabetes and MN by summarizing the evidence from the Mendelian randomization (MR) study.

METHODS

The statistical data for MN was obtained from a GWAS study encompassing 7979 individuals. Regarding diabetes, fasting glucose, fasting insulin, and HbA1C data, we accessed the UK-Biobank, within family GWAS consortium, MAGIC, FinnGen database, MRC-IEU, and Neale Lab, which provided sample sizes ranging from 17,724 to 298,957. As a primary method in this MR analysis, we employed the Inverse Variance Weighted (IVW), Weighted Median, Weighted mode, MR-Egger, Mendelian randomization pleiotropy residual sum, and outlier (MR-PRESSO) and Leave-one-out sensitivity test. Reverse MR analysis was utilized to investigate whether MN affects Diabetes. Meta-analysis was applied to combine study-specific estimates.

RESULTS

It has been determined that type 2 diabetes, gestational diabetes, type 1 diabetes with or without complications, maternal diabetes, and insulin use pose a risk to MN. Based on the genetic prediction, fasting insulin, fasting blood glucose, and HbA1c levels were not associated with the risk of MN. No heterogeneity, horizontal pleiotropy, or reverse causal relationships were found. The meta-analysis results further validated the accuracy.

CONCLUSIONS

The MR analysis revealed the association between MN and various subtypes of diabetes. This study has provided a deeper understanding of the pathogenic mechanisms connecting MN and diabetes.

Major depressive disorder elevates the risk of dentofacial deformity: a bidirectional two-sample Mendelian randomization study

Background

The association between psychiatric disorders and dentofacial deformities has attracted widespread attention. However, their relationship is currently unclear and controversial.

Methods

A two-sample bidirectional MR analysis was performed to study the causal relationship between dentofacial deformity and eight psychiatric disorders, including major depressive disorder, panic disorder, schizophrenia, bipolar disorder, attention deficit hyperactivity disorder, Alzheimer's disease, autism spectrum disorder, and neuroticism. Inverse variance weighted, weighted median, MR-Egger regression, weighted mode four methods, and further sensitivity analyses were conducted.

Results

The major depressive disorder affected dentofacial deformity, with an OR = 1.387 (95% CI = 1.181-1.629, P = 6.77×10-5). No other psychiatric disorders were found to be associated with dentofacial deformity. In turn, dentofacial deformity were associated with neuroticism, with an OR = 1.050 (95% CI = 1.008-1.093, P = 0.018). And there was no evidence that dentofacial deformity would increase the risk of other psychiatric disorders.

Conclusions

Major depressive disorder might elevate the risk of dentofacial deformities, and dentofacial deformity conditions would increase the risk of the incidence of neuroticism.

Association of mental disorders with sepsis: a bidirectional Mendelian randomization study

Background

Substantial research evidence supports the correlation between mental disorders and sepsis. Nevertheless, the causal connection between a particular psychological disorder and sepsis remains unclear.

Methods

For investigating the causal relationships between mental disorders and sepsis, genetic variants correlated with mental disorders, including anorexia nervosa (AN), attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), bipolar disorder (BD), major depressive disorder (MDD), obsessive-compulsive disorder (OCD), panic disorder (PD), posttraumatic stress disorder (PTSD), schizophrenia (SCZ), and tourette syndrome (TS), were all extracted from the Psychiatric Genomics Consortium (PGC). The causal estimates and direction between these mental disorders and sepsis were evaluated employing a two-sample bidirectional MR strategy. The inverse variance weighted (IVW) method was the primary approach utilized. Various sensitivity analyses were performed to confirm the validity of the causal effect. Meta-analysis, multivariable MR, and mediation MR were conducted to ensure the credibility and depth of this research.

Results

The presence of AN was in relation to a greater likelihood of sepsis (OR 1.08, 95% CI 1.02-1.14; p = 0.013). A meta-analysis including validation cohorts supported this observation (OR 1.06, 95% CI 1.02-1.09). None of the investigated mental disorders appeared to be impacted when sepsis was set as the exposure factor. Even after adjusting for confounding factors, AN remained statistically significant (OR 1.08, 95% CI 1.02-1.15; p = 0.013). Mediation analysis indicated N-formylmethionine levels (with a mediated proportion of 7.47%), cystatin D levels (2.97%), ketogluconate Metabolism (17.41%) and N10-formyl-tetrahydrofolate biosynthesis (20.06%) might serve as mediators in the pathogenesis of AN-sepsis.

Conclusion

At the gene prediction level, two-sample bidirectional MR analysis revealed that mental disorder AN had a causal association with an increased likelihood of sepsis. In addition, N-formylmethionine levels, cystatin D levels, ketogluconate metabolism and N10-formyl-tetrahydrofolate biosynthesis may function as potential mediators in the pathophysiology of AN-sepsis. Our research may contribute to the investigation of novel therapeutic strategies for mental illness and sepsis.

Maternal diabetes and risk of attention-deficit/hyperactivity disorder in offspring in a multinational cohort of 3.6 million mother-child pairs

Previous studies report an association between maternal diabetes mellitus (MDM) and attention-deficit/hyperactivity disorder (ADHD), often overlooking unmeasured confounders such as shared genetics and environmental factors. We therefore conducted a multinational cohort study with linked mother-child pairs data in Hong Kong, New Zealand, Taiwan, Finland, Iceland, Norway and Sweden to evaluate associations between different MDM (any MDM, gestational diabetes mellitus (GDM) and pregestational diabetes mellitus (PGDM)) and ADHD using Cox proportional hazards regression. We included over 3.6 million mother-child pairs between 2001 and 2014 with follow-up until 2020. Children who were born to mothers with any type of diabetes during pregnancy had a higher risk of ADHD than unexposed children (pooled hazard ratio (HR) = 1.16, 95% confidence interval (CI) = 1.08-1.24). Higher risks of ADHD were also observed for both GDM (pooled HR = 1.10, 95% CI = 1.04-1.17) and PGDM (pooled HR = 1.39, 95% CI = 1.25-1.55). However, siblings with discordant exposure to GDM in pregnancy had similar risks of ADHD (pooled HR = 1.05, 95% CI = 0.94-1.17), suggesting potential confounding by unmeasured, shared familial factors. Our findings indicate that there is a small-to-moderate association between MDM and ADHD, whereas the association between GDM and ADHD is unlikely to be causal. This finding contrast with previous studies, which reported substantially higher risk estimates, and underscores the need to reevaluate the precise roles of hyperglycemia and genetic factors in the relationship between MDM and ADHD.

Association between gastroesophageal reflux disease and stroke: a bidirectional Mendelian randomization study

Objective

Some previous studies have suggested a potential link between stroke and gastroesophageal reflux disease (GERD). We used a two-sample bidirectional Mendelian randomization (MR) method to explore the causal relationship between stroke and GERD.

Design

Summary-level data derived from the published genome-wide association studies (GWAS) were employed for analyses. Single-nucleotide polymorphisms (SNPs) as instrumental variables (IVs) for stroke (n = 446,696) and its common subtypes ischemic stroke (IS) (n = 440,328), large vessel stroke (LVS) (n = 410,484), small vessel stroke (SVS) (n = 198,048), and cardioembolic stroke (CES) (n = 413,304) were obtained from the MEGASTROKE consortium. The data on intracerebral hemorrhage (ICH) (n = 721,135) come from the UK Biobank. Instrumental variables (IVs) for lacunar stroke (LS) (n = 474,348) and GERD (n = 602,604) were screened from publicly available genetic summary data. The inverse variance weighted (IVW) method was used as the main MR method. Pleiotropy was detected by the MR-Egger intercept test, MR pleiotropy residual sum and outlier, and leave-one-out analysis. Cochran Q statistics were used as supplements to detect pleiotropy.

Results

We found that GERD can causally increase the risk of stroke [IVW odds ratio (OR): 1.22, 95% confidence interval (CI): 1.13-1.32, p = 1.16 × 10-6] and its common subtypes IS (OR: 1.19, 95% CI: 1.10-1.30, p = 3.22 × 10-5), LVS (OR: 1.49, 95% CI: 1.21-1.84, p = 1.47 × 10-4), and LS (OR: 1.20, 95% CI: 1.001-1.44, p = 0.048). Several important risk factors for stroke have also been implicated in the above causal relationship, including type 2 diabetes, sleep apnea syndrome, high body mass index, high waist-to-hip ratio, and elevated serum triglyceride levels. In reverse MR analysis, we found that overall stroke (OR: 1.09, 95% CI: 1.004-1.19, p = 0.039) and IS (OR: 1.10, 95% CI: 1.03-1.17, p = 0.007) have the causal potential to enhance GERD risk.

Conclusion

This MR study provides evidence supporting a causal relationship between GERD and stroke and some of its common subtypes. We need to further explore the interconnected mechanisms between these two common diseases to better prevent and treat them.

Psychotropic Drug-Related Weight Gain and Its Treatment

Psychotropic drug-related weight gain (PDWG) is a common occurrence and is highly associated with non-initiation, discontinuation, and dissatisfaction with psychiatric drugs. Moreover, PDWG intersects with the elevated risk for obesity and associated morbidity that has been amply reported in the psychiatric population. Evidence indicates that differential liability for PDWG exists for antipsychotics, antidepressants, and anticonvulsants. During the past two decades, agents within these classes have become available with significantly lower or no liability for PDWG and as such should be prioritized. Although lithium is associated with weight gain, the overall extent of weight gain is significantly lower than previously estimated. The benefit of lifestyle and behavioral modification for obesity and/or PDWG in psychiatric populations is established, with effectiveness similar to that in the general population. Metformin is the most studied pharmacological treatment in the prevention and treatment of PDWG, and promising data are emerging for glucagon-like peptide-1 (GLP-1) receptor agonists (e.g., liraglutide, exenatide, semaglutide). Most pharmacologic antidotes for PDWG are supported with low-confidence data (e.g., topiramate, histamine-2 receptor antagonists). Future vistas for pharmacologic treatment for PDWG include large, adequately controlled studies with GLP-1 receptor agonists and possibly GLP-1/glucose-dependent insulinotropic polypeptide co-agonists (e.g., tirzepatide) as well as specific dietary modifications.

The causal relationship between risk of developing bronchial asthma and frailty: a bidirectional two-sample Mendelian randomization study

Background

A potential link between asthma and frailty has been suggested in previous studies. However, the nature of the causal relationship between these two conditions warrants further investigation. Therefore, this study assessed the bidirectional causality between asthma and frailty risk using two-sample Mendelian randomization (MR).

Methods

The study data were obtained from the genome-wide association study (GWAS) dataset, with 337,159 samples representing asthma data and 175,226 samples representing frailty. The causal relationship between the two disorders was assessed by selecting the single nucleotide polymorphisms (SNPs), significantly associated with both asthma and frailty. The inverse variance weighting (IVW) method was used as the main analytical method to estimate the possible influence of causality. Sensitivity analysis was also performed using Mr-Egger intercept, funnel plot, "leave-one-out," and Cochran Q test. In addition, potential mediators were investigated by risk factor analysis.

Result

The IVW method showed an increased risk of frailty due to increased genetic susceptibility factors and the number of to asthma (OR = 2.325, 95%CI:1.958-2.761; p = 6.527498e-22), while no horizontal pleiotropy was observed for the Mr-Egger intercept (p = 0.609) and the funnel plot. The Cochran Q value was 72.858, p = 0.024, and there was heterogeneity in the Cochran Q-value. No single SNP was observed for "leave-one-out" that had a biasing effect on the instrumental variables. In addition, genetic susceptibility to frailty was associated with asthma (OR = 1.088, 95%CI:1.058-1.119; p = 4.815589e-09). In the causal relationship described above, several risk factors for frailty are complex, with asthma leading to a significant reduction in physical activity endurance.

Conclusion

Our findings suggest a probable positive causal effect of asthma on the risk of developing frailty, potentially mediated by reduced physical activity endurance. At the same time, a causal relationship exists between frailty and asthma. Therefore, assessment strategies for frailty should include asthma and vice versa.

Mendelian randomization analyses identify bidirectional causal relationships of obesity with psychiatric disorders

BACKGROUND

Obesity have been showed to be strongly associated with psychiatric disorders, but the exact causality and the direction of the relationship remain inconclusive. Thus, we aimed to identify the causal associations between obesity and psychiatric disorders using two-sample Mendelian randomization (MR).

METHODS

Single-nucleotide polymorphisms associated with obesity, including body mass index (BMI), waist-hip ratio (WHR), and waist-hip ratio adjusted for BMI (WHRadjBMI), were extracted from a genome-wide association study of 694,649 European ancestry from the GIANT consortium. Summary level data for 10 psychiatric disorders were obtained from the Psychiatric Genomics Consortium. Inverse-variance weighted (IVW) method was used as the primary analysis, while several sensitivity analyses were applied to evaluate heterogeneity and pleiotropy.

RESULTS

The main MR results suggested higher BMI or WHR was positively causally associated with an increased risk of attention deficit hyperactivity disorder (ADHD), anorexia nervosa (AN), post-traumatic stress disorder (PTSD), major depressive disorder (MDD) and Alzheimer's disease (ALZ), but negatively causally associated with an increased risk of obsessive-compulsive disorder (OCD) and schizophrenia. For the reverse direction, ADHD and MDD were associated with an increased risk of obesity, but schizophrenia and ALZ were associated with a decreased risk of obesity.

CONCLUSION

Our findings support evidence of causal relationships between obesity and ADHD, MDD, PTSD, ALZ, SCZ, AN, and OCD, and confirmed the bidirectional causal relationships between obesity and ADHD, MDD, SCZ, and ALZ.

Causality between sarcopenia-related traits and major depressive disorder: A bi-directional, two-sample Mendelian randomized study

Observational studies have demonstrated an association between sarcopenia and depression. However, these studies may be influenced by confounding factors, and the causal relationship between sarcopenia and major depressive disorder (MDD) remains unclear. This study aimed to apply the Mendelian randomization (MR) method to address confounding factors and assess the causal effect of sarcopenia on MDD. A two-way, two-sample MR method was employed in this study. Instrumental variables of genome-wide significance level were obtained from the open large-scale genome-wide association study summary data. MR analysis was conducted using inverse variance weighted, MR-Egger, and weighted median methods. The reliability of the results was verified using the heterogeneity test, pleiotropy test, and leave-one-out method for sensitivity analysis. Grip strength (right-hand grip strength: odds ratio [OR] = 0.880, 95% confidence interval [CI] 0.786-0.987, P = .027; left-hand grip strength: OR = 0.814, 95% CI 0.725-0.913, P < .001) and usual walking pace (OR = 0.673, 95% CI 0.506-0.896, P = .007) exhibited a direct causal effect on MDD. MDD had a significant causal effect on appendicular lean mass (β = -0.065, 95% CI -0.110, -0.019, P = .005). There was a causal relationship between sarcopenia-related traits and MDD. Loss of muscle strength, rather than skeletal muscle mass, is correlated with an increased risk of MDD. Furthermore, individuals with MDD are more likely to experience loss of skeletal muscle mass.

Comorbidity between major depressive disorder and physical diseases: a comprehensive review of epidemiology, mechanisms and management

Populations with common physical diseases - such as cardiovascular diseases, cancer and neurodegenerative disorders - experience substantially higher rates of major depressive disorder (MDD) than the general population. On the other hand, people living with MDD have a greater risk for many physical diseases. This high level of comorbidity is associated with worse outcomes, reduced adherence to treatment, increased mortality, and greater health care utilization and costs. Comorbidity can also result in a range of clinical challenges, such as a more complicated therapeutic alliance, issues pertaining to adaptive health behaviors, drug-drug interactions and adverse events induced by medications used for physical and mental disorders. Potential explanations for the high prevalence of the above comorbidity involve shared genetic and biological pathways. These latter include inflammation, the gut microbiome, mitochondrial function and energy metabolism, hypothalamic-pituitary-adrenal axis dysregulation, and brain structure and function. Furthermore, MDD and physical diseases have in common several antecedents related to social factors (e.g., socioeconomic status), lifestyle variables (e.g., physical activity, diet, sleep), and stressful live events (e.g., childhood trauma). Pharmacotherapies and psychotherapies are effective treatments for comorbid MDD, and the introduction of lifestyle interventions as well as collaborative care models and digital technologies provide promising strategies for improving management. This paper aims to provide a detailed overview of the epidemiology of the comorbidity of MDD and specific physical diseases, including prevalence and bidirectional risk; of shared biological pathways potentially implicated in the pathogenesis of MDD and common physical diseases; of socio-environmental factors that serve as both shared risk and protective factors; and of management of MDD and physical diseases, including prevention and treatment. We conclude with future directions and emerging research related to optimal care of people with comorbid MDD and physical diseases.

Childhood internalizing and externalizing problems and cardiovascular and diabetes mellitus risk in adolescence

BACKGROUND

Among adults, common psychopathology is a risk factor for cardiovascular diseases (CVD) and type 2 diabetes mellitus (T2DM). We investigated whether childhood internalizing and externalizing problems are prospectively associated with clinically elevated CVD and T2DM risk factors in adolescence.

METHODS

Data were from the Avon Longitudinal Study of Parents and Children. Childhood internalizing (emotional) and externalizing (hyperactivity and conduct) problems were rated on the Strengths and Difficulties Questionnaire (parent version) (N = 6442). BMI was measured at age 15 and triglycerides, low-density lipoprotein cholesterol and homeostasis model assessment of insulin resistance, IR, were assessed at age 17. We estimated associations using multivariate log-linear regression. Models were adjusted for confounding and participants attrition.

RESULTS

Children with hyperactivity or conduct problems were more likely to become obese and to develop clinically high levels of triglycerides and HOMA-IR in adolescence. In fully adjusted models, IR was associated with hyperactivity (relative risk, RR = 1.35, 95 % confidence interval, CI = 1.00-1.81) and conduct problems (RR = 1.37, CI = 1.06-1.78). High triglycerides were associated with hyperactivity (RR = 2.05, CI = 1.41-2.98) and with conduct problems (RR = 1.85, CI = 1.32-2.59). BMI only minimally explained these associations. Emotional problems were not associated with increased risk.

LIMITATIONS

Residual attrition bias, reliance on parent's reports of children's behaviors, non-diverse sample.

CONCLUSIONS

This research suggests that childhood externalizing problems might be a novel independent risk factor for CVD/T2DM. Future research should corroborate these findings and investigate mechanisms. Pediatricians may need to assess and treat CVD/T2DM risk factors in adolescents with a history of externalizing problems.

Shared genetics and bidirectional causal relationships between type 2 diabetes and attention-deficit/hyperactivity disorder

Background

Type 2 diabetes (T2D) is a chronic metabolic disorder with high comorbidity with mental disorders. The genetic links between attention-deficit/hyperactivity disorder (ADHD) and T2D have yet to be elucidated.

Aims

We aim to assess shared genetics and potential associations between ADHD and T2D.

Methods

We performed genetic correlation, two-sample Mendelian randomisation and polygenic overlap analyses between ADHD and T2D. The genome-wide association study (GWAS) summary results of T2D (80 154 cases and 853 816 controls), ADHD2019 (20 183 cases and 35 191 controls from the 2019 GWAS ADHD dataset) and ADHD2022 (38 691 cases and 275 986 controls from the 2022 GWAS ADHD dataset) were used for the analyses. The T2D dataset was obtained from the DIAGRAM Consortium. The ADHD datasets were obtained from the Psychiatric Genomics Consortium. We compared genome-wide association signals to reveal shared genetic variation between T2D and ADHD using the larger ADHD2022 dataset. Moreover, molecular pathways were constructed based on large-scale literature data to understand the connection between ADHD and T2D.

Results

T2D has positive genetic correlations with ADHD2019 (r_g=0.33) and ADHD2022 (r_g=0.31). Genetic liability to ADHD2019 was associated with an increased risk for T2D (odds ratio (OR): 1.30, p<0.001), while genetic liability to ADHD2022 had a suggestive causal effect on T2D (OR: 1.30, p=0.086). Genetic liability to T2D was associated with a higher risk for ADHD2019 (OR: 1.05, p=0.001) and ADHD2022 (OR: 1.03, p<0.001). The polygenic overlap analysis showed that most causal variants of T2D are shared with ADHD2022. T2D and ADHD2022 have three overlapping loci. Molecular pathway analysis suggests that ADHD and T2D could promote the risk of each other through inflammatory pathways.

Conclusions

Our study demonstrates substantial shared genetics and bidirectional causal associations between ADHD and T2D.