Genetically predicted education attainment in relation to somatic and mental health

An exploration into the causal relationships between educational attainment, intelligence, and wellbeing: an observational and two-sample Mendelian randomisation study

Educational attainment is associated with a range of positive outcomes, yet its impact on wellbeing is unclear, and complicated by high correlations with intelligence. We use genetic and observational data to investigate for the first time, whether educational attainment and intelligence are causally and independently related to wellbeing. Results from our multivariable Mendelian randomisation demonstrated a positive causal impact of a genetic predisposition to higher educational attainment on wellbeing that remained after accounting for intelligence, and a negative impact of intelligence that was independent of educational attainment. Observational analyses suggested that these associations may be subject to sex differences, with benefits to wellbeing greater for females who attend higher education compared to males. For intelligence, males scoring more highly on measures related to happiness were those with lower intelligence. Our findings demonstrate a unique benefit for wellbeing of staying in school, over and above improving cognitive abilities, with benefits likely to be greater for females compared to males.

Factors Associated With the Prevalence of Irritable Bowel Syndrome: The Miyagi Part of the Tohoku Medical Megabank Project Community-based Cohort Study

Background/Aims

The objective of this research is to examine factors related to irritable bowel syndrome (IBS) prevalence in a large population-based study.

Methods

A cross-sectional study was conducted with participants in the Miyagi part of the Tohoku Medical Megabank Project Community-Based cohort study who completed the Rome II Modular Questionnaire. Multivariate odds ratios (ORs) for the presence of IBS and 95% confidence intervals (95% CIs) for the reference group were calculated for each factor. Additionally, a stratified analysis was performed by sex and age group (20-49 years, 50-64 years, and ≥ 65 years).

Results

Among 16 252 participants, 3025 (18.6%) had IBS, comprising 750 men (15.5%) and 2275 women (19.9%). Multivariate ORs for the presence of IBS decreased significantly with each year of age (OR, 0.98; 95% CI, 0.98-0.99). Moreover, compared with the reference group, ORs for the presence of IBS were significantly higher in individuals whose home was partially damaged by the Great East Japan Earthquake, those with < 16 years of education, those who spent less time walking, those with high perceived stress (1.77, 1.57-2.01), those with high psychological distress (1.58, 1.36-1.82), and those with high symptoms of depression (1.76, 1.60-1.94). In stratified analyses, a significant relationship was found between psychological factors and IBS prevalence in all sex and age groups.

Conclusions

This large cross-sectional population-based cohort study identified several factors associated with IBS prevalence. Psychological factors were significantly associated with IBS prevalence across all age groups and sexes.

Evaluating the causal relationship between educational attainment and mental health

We investigate the causal relationship between educational attainment (EA) and mental health using two research designs. First, we compare the relationship between EA and 18 psychiatric diagnoses within sibship in Dutch national registry data (N=1.7 million), thereby controlling for unmeasured familial factors. Second, we apply two-sample Mendelian Randomization, which uses genetic variants related to EA or psychiatric diagnosis as instrumental variables, to test whether there is a causal relation in either direction. Our results suggest that lower levels of EA causally increase the risk of MDD, ADHD, alcohol dependence, GAD and PTSD diagnoses. We also find evidence of a causal effect of ADHD on EA. For schizophrenia, anorexia nervosa, OCD, and bipolar disorder, results were inconsistent across the different approaches, highlighting the importance of using multiple research designs to understand complex relationships such as between EA and mental health.

Modifiable lifestyle factors influencing psychiatric disorders mediated by plasma proteins: A systemic Mendelian randomization study

BACKGROUND

Psychiatric disorders are emerging as a serious public health hazard, influencing an increasing number of individuals worldwide. However, the effect of modifiable lifestyle factors on psychiatric disorders remains unclear.

METHODS

Genome-wide association studies (GWAS) summary statistics were obtained mainly from Psychiatric Genomics Consortium and UK Biobank, with sample sizes varying between 10,000 and 1,200,000. The two-sample Mendelian randomization (MR) method was applied to investigate the causal associations between 45 lifestyle factors and 13 psychiatric disorders, and screen potential mediator proteins from 2992 candidate plasma proteins. We implemented a four-step framework with step-by-step screening incorporating two-step, univariable, and multivariable MR.

RESULTS

We found causal effects of strenuous sports or other exercise on Tourette's syndrome (OR [95%CI]: 0.0047 [5.24E-04-0.042]); lifelong smoking index on attention-deficit hyperactivity disorder (10.53 [6.96-15.93]), anxiety disorders (3.44 [1.95-6.05]), bipolar disorder (BD) (2.25 [1.64-3.09]), BD II (2.89 [1.81-4.62]), and major depressive disorder (MDD) (2.47 [1.90-3.20]); and educational years on anorexia nervosa (AN) (1.47 [1.22-1.76]), and MDD (0.74 [0.66-0.83]). Five proteins were found to have causal associations with psychiatric disorders, namely ADH1B, GHDC, STOM, CD226, and TP63. STOM, a membrane protein deficient in the erythrocytes of hereditary stomatocytosis patients, may mediate the effect of educational attainment on AN.

LIMITATIONS

The mechanisms underlying the effects of lifestyle factors on psychiatric disorders require further investigation.

CONCLUSIONS

These findings could help assess the risk of psychiatric disorders based on lifestyle factors and also support lifestyle interventions as a prevention strategy for mental illness.

Association and mediation between educational attainment and respiratory diseases: a Mendelian randomization study

BACKGROUND

Respiratory diseases are a major health burden, and educational inequalities may influence disease prevalence. We aim to evaluate the causal link between educational attainment and respiratory disease, and to determine the mediating influence of several known modifiable risk factors.

METHODS

We conducted a two-step, two-sample Mendelian randomization (MR) analysis using summary statistics from genome-wide association studies (GWAS) and single nucleotide polymorphisms (SNPs) as instrumental variables for educational attainment and respiratory diseases. Additionally, we performed a multivariable MR analysis to estimate the direct causal effect of each exposure variable included in the analysis on the outcome, conditional on the other exposure variables included in the model. The mediating roles of body mass index (BMI), physical activity, and smoking were also assessed.

FINDINGS

MR analyses provide evidence of genetically predicted educational attainment on the risk of FEV1 (β = 0.10, 95% CI 0.06, 0.14), FVC (β = 0.12, 95% CI 0.07, 0.16), FEV1/FVC (β = - 0.005, 95% CI - 0.05, 0.04), lung cancer (OR = 0.54, 95% CI 0.45, 0.65) and asthma (OR = 0.86, 95% CI 0.78, 0.94). Multivariable MR dicated the effect of educational attainment on FEV1 (β = 0.10, 95% CI 0.04, 0.16), FVC (β = 0.07, 95% CI 0.01, 0.12), FEV1/FVC (β = 0.07, 95% CI 0.01, 0.01), lung cancer (OR = 0.55, 95% CI 0.42, 0.71) and asthma (OR = 0.88, 95% CI 0.78, 0.99) persisted after adjusting BMI and cigarettes per day. Of the 23 potential risk factors, BMI, smoking may partially mediate the relationship between education and lung disease.

CONCLUSION

High levels of educational attainment have a potential causal protective effect on respiratory diseases. Reducing smoking and adiposity may be a target for the prevention of respiratory diseases attributable to low educational attainment.

Risk factors for prostate cancer: An umbrella review of prospective observational studies and mendelian randomization analyses

BACKGROUND

The incidence of prostate cancer is increasing in older males globally. Age, ethnicity, and family history are identified as the well-known risk factors for prostate cancer, but few modifiable factors have been firmly established. The objective of this study was to identify and evaluate various factors modifying the risk of prostate cancer reported in meta-analyses of prospective observational studies and mendelian randomization (MR) analyses.

METHODS AND FINDINGS

We searched PubMed, Embase, and Web of Science from the inception to January 10, 2022, updated on September 9, 2023, to identify meta-analyses and MR studies on prostate cancer. Eligibility criteria for meta-analyses were (1) meta-analyses including prospective observational studies or studies that declared outcome-free at baseline; (2) evaluating the factors of any category associated with prostate cancer incidence; and (3) providing effect estimates for further data synthesis. Similar criteria were applied to MR studies. Meta-analysis was repeated using the random-effects inverse-variance model with DerSimonian-Laird method. Quality assessment was then conducted for included meta-analyses using AMSTAR-2 tool and for MR studies using STROBE-MR and assumption evaluation. Subsequent evidence grading criteria for significant associations in meta-analyses contained sample size, P values and 95% confidence intervals, 95% prediction intervals, heterogeneity, and publication bias, assigning 4 evidence grades (convincing, highly suggestive, suggestive, or weak). Significant associations in MR studies were graded as robust, probable, suggestive, or insufficient considering P values and concordance of effect directions. Finally, 92 selected from 411 meta-analyses and 64 selected from 118 MR studies were included after excluding the overlapping and outdated studies which were published earlier and contained fewer participants or fewer instrument variables for the same exposure. In total, 123 observational associations (45 significant and 78 null) and 145 causal associations (55 significant and 90 null) were categorized into lifestyle; diet and nutrition; anthropometric indices; biomarkers; clinical variables, diseases, and treatments; and environmental factors. Concerning evidence grading on significant associations, there were 5 highly suggestive, 36 suggestive, and 4 weak associations in meta-analyses, and 10 robust, 24 probable, 4 suggestive, and 17 insufficient causal associations in MR studies. Twenty-six overlapping factors between meta-analyses and MR studies were identified, with consistent significant effects found for physical activity (PA) (occupational PA in meta: OR = 0.87, 95% CI: 0.80, 0.94; accelerator-measured PA in MR: OR = 0.49, 95% CI: 0.33, 0.72), height (meta: OR = 1.09, 95% CI: 1.06, 1.12; MR: OR = 1.07, 95% CI: 1.01, 1.15, for aggressive prostate cancer), and smoking (current smoking in meta: OR = 0.74, 95% CI: 0.68, 0.80; smoking initiation in MR: OR = 0.91, 95% CI: 0.86, 0.97). Methodological limitation is that the evidence grading criteria could be expanded by considering more indices.

CONCLUSIONS

In this large-scale study, we summarized the associations of various factors with prostate cancer risk and provided comparisons between observational associations by meta-analysis and genetically estimated causality by MR analyses. In the absence of convincing overlapping evidence based on the existing literature, no robust associations were identified, but some effects were observed for height, physical activity, and smoking.

Exploring the influences of education, intelligence and income on mental disorders

Background

Previous studies have shown that educational attainment (EA), intelligence and income are key factors associated with mental disorders. However, the direct effects of each factor on major mental disorders are unclear.

Aims

We aimed to evaluate the overall and independent causal effects of the three psychosocial factors on common mental disorders.

Methods

Using genome-wide association study summary datasets, we performed Mendelian randomisation (MR) and multivariable MR (MVMR) analyses to assess potential associations between the 3 factors (EA, N=766 345; household income, N=392 422; intelligence, N=146 808) and 13 common mental disorders, with sample sizes ranging from 9907 to 807 553. Inverse-variance weighting was employed as the main method in the MR analysis.

Results

Our MR analysis showed that (1) higher EA was a protective factor for eight mental disorders but contributed to anorexia nervosa, obsessive-compulsive disorder (OCD), bipolar disorder (BD) and autism spectrum disorder (ASD); (2) higher intelligence was a protective factor for five mental disorders but a risk factor for OCD and ASD; (3) higher household income protected against 10 mental disorders but confers risk for anorexia nervosa. Our MVMR analysis showed that (1) higher EA was a direct protective factor for attention-deficit/hyperactivity disorder (ADHD) and insomnia but a direct risk factor for schizophrenia, BD and ASD; (2) higher intelligence was a direct protective factor for schizophrenia but a direct risk factor for major depressive disorder (MDD) and ASD; (3) higher income was a direct protective factor for seven mental disorders, including schizophrenia, BD, MDD, ASD, post-traumatic stress disorder, ADHD and anxiety disorder.

Conclusions

Our study reveals that education, intelligence and income intertwine with each other. For each factor, its independent effects on mental disorders present a more complex picture than its overall effects.

Understanding the educational inequalities in suicide attempts and their mediators: a Mendelian randomisation study

Background

Educational inequalities in suicide have become increasingly prominent over the past decade. Elucidating modifiable risk factors that serve as intermediaries in the impact of low educational attainment on suicide has the potential to reduce health disparities.

Aims

To examine the risk factors that mediate the relationship between educational attainment and suicide attempts and quantify their contributions to the mediation effect.

Methods

We conducted a two-sample Mendelian randomisation (MR) analysis to estimate the causal effect of educational attainment on suicide attempts, utilising genome-wide association study summary statistics from the Integrative Psychiatric Research (iPSYCH; 6024 cases and 44 240 controls) and FinnGen (8978 cases and 368 299 controls). We systematically evaluated 42 putative mediators within the causal pathway connecting reduced educational attainment to suicide attempts and employed two-step and multivariable MR to quantify the proportion of the mediated effect.

Results

In the combined analysis of iPSYCH and FinnGen, each standard deviation (SD) decrease in genetically predicted educational attainment (equating to 3.4 years of education) was associated with a 105% higher risk of suicide attempts (odds ratio (OR): 2.05; 95% confidence interval (CI): 1.81 to 2.31). Of the 42 risk factors analysed, the two-step MR identified five factors that mediated the association between educational attainment and suicide attempts. The respective proportions of mediation were 47% (95% CI: 29% to 66%) for smoking behaviour, 36% (95% CI: 0% to 84%) for chronic pain, 49% (95% CI: 36% to 61%) for depression, 35% (95% CI: 12% to 59%) for anxiety and 26% (95% CI: 18% to 34%) for insomnia. Multivariable MR implicated these five mediators collectively, accounting for 68% (95% CI: 40% to 96%) of the total effect.

Conclusions

This study identified smoking, chronic pain and mental disorders as primary intervention targets for attenuating suicide risk attributable to lower educational levels in the European population.

Leisure time television watching, computer use and risks of breast, colorectal and prostate cancer: A Mendelian randomisation analysis

BACKGROUND

Sedentary behaviours have been associated with increased risks of some common cancers in epidemiological studies; however, it is unclear if these associations are causal.

METHODS

We used univariable and multivariable two-sample Mendelian randomisation (MR) to examine potential causal relationships between sedentary behaviours and risks of breast, colorectal and prostate cancer. Genetic variants associated with self-reported leisure television watching and computer use were identified from a recent genome-wide association study (GWAS). Data related to cancer risk were obtained from cancer GWAS consortia. A series of sensitivity analyses were applied to examine the robustness of the results to the presence of confounding.

RESULTS

A 1-standard deviation (SD: 1.5 h/day) increment in hours of television watching increased risk of breast cancer (OR per 1-SD: 1.15, 95% confidence interval [CI]: 1.05-1.26) and colorectal cancer (OR per 1-SD: 1.32, 95% CI: 1.16-1.49) while there was little evidence of an association for prostate cancer risk (OR per 1-SD: 0.94, 95% CI: 0.84-1.06). After adjusting for years of education, the effect estimates for television watching were attenuated (breast cancer, OR per 1-SD: 1.08, 95% CI: 0.92-1.27; colorectal cancer, OR per 1-SD: 1.08, 95% CI: 0.90-1.31). Post hoc analyses showed that years of education might have a possible confounding and mediating role in the association between television watching with breast and colorectal cancer. Consistent results were observed for each cancer site according to sex (colorectal cancer), anatomical subsites and cancer subtypes. There was little evidence of associations between genetically predicted computer use and cancer risk.

CONCLUSIONS

Our univariable analysis identified some positive associations between hours of television watching and risks of breast and colorectal cancer. However, further adjustment for additional lifestyle factors especially years of education attenuated these results. Future studies using objective measures of exposure can provide new insights into the possible role of sedentary behaviour in cancer development.

Mendelian randomization studies of depression: evidence, opportunities, and challenges

BACKGROUND

Major depressive disorder (MDD) poses a significant social and economic burden worldwide. Identifying exposures, risk factors, and biological mechanisms that are causally connected to MDD can help build a scientific basis for disease prevention and development of novel therapeutic approaches.

METHODS

In this systematic review, we assessed the evidence for causal relationships between putative causal risk factors and MDD from Mendelian randomization (MR) studies, following PRISMA. We assessed methodological quality based on key elements of the MR design: use of a full instrumental variable analysis and validation of the three key MR assumptions.

RESULTS

We included methodological details and results from 52 articles. A causal link between lifestyle, metabolic, inflammatory biomarkers, particular pathological states and MDD is supported by MR investigations, although results for each category varied substantially.

CONCLUSIONS

While this review shows how MR can offer useful information for examining prospective treatment targets and better understanding the pathophysiology of MDD, some methodological flaws in the existing literature limit reliability of results and probably underlie their heterogeneity. We highlight perspectives and recommendations for future works on MR in psychiatry.

Predictive risk factors before the onset of familial rheumatoid arthritis: the Tatarstan cohort study

Background

A familial history of rheumatoid arthritis (RA) predisposes an individual to develop RA. This study aimed at investigating factors associated with this conversion from the Tatarstan cohort.

Methods

A total of 144 individuals, referred to as pre-RA and at risk for familial RA, were selected 2 years (range: 2-21 years) before conversion to RA and compared to non-converted 328 first-degree relatives (FDR) from RA as assessed after ≥2 years follow-up, and 355 healthy controls were also selected (HC). Preclinical parameters and socio-demographic/individual/HLA genetic factors were analyzed when data were available at the time of enrollment.

Results

As compared to FDR and HC groups, pre-RA individuals were characterized before conversion to RA by the presence of arthralgia, severe morning symptoms, a lower educational level, and rural location. An association with the HLA-DRB1 SE risk factor was also retrieved with symmetrical arthralgia and passive smoking. On the contrary, alcohol consumption and childlessness in women were protective and associated with the HLA-DRB1*07:01 locus.

Conclusion

Before RA onset, a combination of individual and genetic factors characterized those who are at risk of progressing to RA among those with familial RA relatives.

Appraising causal risk and protective factors for rheumatoid arthritis

Aims

Mendelian randomization (MR) is considered to overcome the bias of observational studies, but there is no current meta-analysis of MR studies on rheumatoid arthritis (RA). The purpose of this study was to summarize the relationship between potential pathogenic factors and RA risk based on existing MR studies.

Methods

PubMed, Web of Science, and Embase were searched for MR studies on influencing factors in relation to RA up to October 2022. Meta-analyses of MR studies assessing correlations between various potential pathogenic factors and RA were conducted. Random-effect and fixed-effect models were used to synthesize the odds ratios of various pathogenic factors and RA. The quality of the study was assessed using the Strengthening the Reporting of Observational Studies in Epidemiology using Mendelian Randomization (STROBE-MR) guidelines.

Results

A total of 517 potentially relevant articles were screened, 35 studies were included in the systematic review, and 19 studies were eligible to be included in the meta-analysis. Pooled estimates of 19 included studies (causality between 15 different risk factors and RA) revealed that obesity, smoking, coffee intake, lower education attainment, and Graves' disease (GD) were related to the increased risk of RA. In contrast, the causality contribution from serum mineral levels (calcium, iron, copper, zinc, magnesium, selenium), alcohol intake, and chronic periodontitis to RA is not significant.

Conclusion

Obesity, smoking, education attainment, and GD have real causal effects on the occurrence and development of RA. These results may provide insights into the genetic susceptibility and potential biological pathways of RA.

Factors Associated with Depression, Anxiety, and Somatic Symptoms among International Salespeople in the Medical Device Industry: A Cross-Sectional Study in China

BACKGROUND

The physical and mental health of corporate employees is equally important, especially for international salespeople in the in vitro diagnostic (IVD) medical device industry. The rapid growth of the IVD market is driven by the increasing prevalence of chronic and infectious diseases. This study aims to determine the prevalence of depression, anxiety, and somatic symptoms among international salespeople in China's IVD industry and identify the association of socio-demographic, occupational, organizational, and psychosocial factors with mental health outcomes for depression, anxiety, and somatic symptoms in Chinese IVD international salespeople.

METHODS

The study was a cross-sectional survey of international salespeople (ISs) in IVD companies officially registered in China. An online survey was designed to collect data through email contact with IVD companies and social media between August 2022 and March 2023. Measured factors included effort-reward imbalance (ERI), health-promoting leadership (HPL), health climate (HC), inner strength (IS), and perceived social support (PSS). Mental health outcomes assessed using the Core Symptom Index (CSI) were depression, anxiety, and somatic symptoms.

RESULTS

A total of 244 salespeople responded to the survey. CSI scores indicated that 18.4% (n = 45) and 10.2% (n = 25) of the respondents had symptoms of major depression and anxiety, respectively. ERI was positively correlated, while the IS and PSS were negatively correlated with major depression, anxiety, and somatic symptoms (p < 0.01). The health climate was negatively correlated with major depression (p < 0.05). Education background was associated with somatic symptoms (p < 0.05). ERI, IS, and gender were significant predictors of major depression, anxiety, and somatic symptoms (p < 0.05).

CONCLUSION

The prevalence of depression and anxiety in China's IVD international salespeople was considered low compared with the prevalence in Chinese populations during COVID-19 but higher than those before the pandemic. Effort-reward imbalance, inner strength, and gender were significant factors in major depression, anxiety, and somatic symptoms among IVD international salespeople.

How education level affects postoperative rehabilitation and follow-up: a single-center experience

BACKGROUND

Radical prostatectomy remains the fundamental treatment for prostate cancer, and improving patients' compliance with postoperative follow-ups is essential for improving patients' quality of life. This study investigates the effect of education levels on patients' recovery and follow-up after radical prostatectomy.

METHODS

Data from 1,112 patients undergoing radical prostatectomy between 2011 and 2020 were collected using medical records, and "pc-follow" systems were used to collect patients' baseline information, education level, pathological information, number of outpatient visits, the time interval between each visit, and PSA test data.

RESULTS

Regarding postoperative outpatient data, there was no difference in the number of outpatient visits among the different education level groups in Shanghai (P = 0.063). A significant difference was found in the interval between outpatient visits among the groups (P < 0.001). Furthermore, significant differences were detected in the number and duration of outpatient clinic visits among the education level groups in all patients (P = 0.016, P = 0.0027). By contrast, no significant difference was found in the recovery time of urinary continence between all patients and those in Shanghai, grouped according to education level (P = 0.082, P = 0.68). For all patients and patients in the Shanghai area, the number of PSA follow-ups increased gradually with an increasing level of education (P < 0.001, P = 0.0029).

CONCLUSIONS

Education level affected the number of postoperative clinic visits, compliance, and the number of PSA tests. However, no significant effect on the recovery of urinary continence was found. Further, clinicians must increase their focus on patients with low education levels to achieve equitable access to health services for all patients.

Leisure time sedentary behaviour and risks of breast, colorectal, and prostate cancer: A Mendelian randomization analysis

Sedentary behaviours have been associated with increased risks of some common cancers in epidemiological studies; however, it is unclear if these associations are causal. We examined potential causal associations between self-reported leisure television watching and computer use and risks of breast, colorectal, and prostate cancer using a two-sample Mendelian randomization framework. Genetic variants were identified from a recent genome-wide association study (GWAS). Cancer data were obtained from cancer GWAS consortia. Additional sensitivity analyses were applied to examine the robustness of the results. A 1-standard deviation increment in hours of television watching increased risk of breast (OR: 1.15, 95% confidence interval [CI]: 1.05,1.26) and colorectal cancer (OR: 1.32, 95%CI: 1.16,1.49) with little evidence of an association for prostate cancer risk. In multivariable models adjusted for years of education, the effect estimates for television watching were attenuated (breast cancer, OR: 1.08, 95%CI: 0.92,1.27; colorectal cancer, OR: 1.08, 95%CI: 0.90,1.31). Post-hoc analyses showed that years of education might have a possible confounding and mediating role in the association between television watching with breast and colorectal cancer. Consistent results were observed by sex (colorectal cancer), anatomical subsites, and cancer subtypes. There was little evidence of associations between computer use and cancer risk. We found evidence of positive associations between hours of television watching and risks of breast and colorectal cancer. However, these findings should be interpreted cautiously given the complex role of education. Future studies using objective measures of exposure can provide new insights into the possible role of sedentary behaviour in cancer development.

Novelty and impact

Evidence from observational studies that examined associations between sedentary behaviours and common cancers is mixed and causality is uncertain. In our Mendelian randomization analyses, higher levels of leisure television watching were found to increase the risks of breast and colorectal cancer, suggesting that the that the promotion of lowering sedentary behaviour time could be an effective strategy in the primary prevention of these commonly diagnosed cancers.

Article category

Cancer Epidemiology.

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.

Diet, Lifestyle Behaviours and Other Risk Factors Associated With Type 2 Diabetes Beyond Body Mass Index: A Mendelian Randomization Study

OBJECTIVES

Our aim in this study was to identify promising targets for the prevention of type 2 diabetes in addition to weight loss. We conducted a Mendelian randomization (MR) study to investigate the body mass index (BMI)-independent associations of 16 risk factors, including diet, lifestyle behaviours and others, with type 2 diabetes.

METHODS

We selected genetic variants as instrumental variables for diet, sleep traits, smoking, physical activity, education and blood pressure (BP) from European-descent genome-wide association studies (GWASs). Summary statistics for type 2 diabetes were derived from a recent GWAS with 74,124 European cases and 824,006 European controls. The inverse-variance weighted MR method was used to assess the associations of the risk factors with type 2 diabetes, followed by validation of robustness using different MR methods in sensitivity analyses.

RESULTS

Genetically predicted insomnia (odds ratio [OR], 1.10; 95% confidence interval [CI], 1.06 to 1.15), smoking initiation (OR, 1.14; 95% CI, 1.06 to 1.21), educational level (OR, 0.69; 95% CI, 0.65 to 0.74), hypertension (OR, 6.50; 95% CI, 3.13 to 13.50), systolic BP (OR, 1.02; 95% CI, 1.02 to 1.03) and diastolic BP (OR, 1.03; 95% CI, 1.02 to 1.03) had BMI-independent effects on type 2 diabetes risk. In addition, alcohol dependence (OR, 1.10; 95% CI, 1.05 to 1.16; BMI-adjusted OR, 1.04; 95% CI, 0.98 to 1.09) and vegetarian diet (OR, 0.50; 95% CI, 0.33 to 0.74; BMI-adjusted OR, 0.78; 95% CI, 0.57 to 1.06) appeared to be correlated with type 2 diabetes via a BMI-mediated pathway. Sensitivity analyses further confirmed the relationship between these factors and type 2 diabetes.

CONCLUSIONS

In this systematic MR study, insomnia, smoking, education and BP had BMI-independent causal effects on the risk of type 2 diabetes, whereas alcohol dependence and vegetarian diet were associated with type 2 diabetes through BMI.

Age at menarche relates to depression in adolescent girls: Comparing a clinical sample to the general pediatric population

CONTEXT

The timing of puberty, physical features of pubertal development, and hormones are closely intertwined but may also individually contribute to the risk for depression and depression severity. Additionally, their effects on mood may depend on depression severity, but previously this has only been studied in mostly subclinical depression.

METHODS

In 184 girls from a single psychiatric hospital with significant depressive symptoms (Beck Depression Inventory-II score > 13), the relationship between depression severity and age at menarche (AAM), pubertal status, and gonadal/adrenal hormones (estradiol, progesterone, DHEA-S, androstenedione, testosterone, dihydrotestosterone) was investigated. Moreover, AAM in depressed girls was compared to that from a representative sample of German adolescents without a psychiatric disorder (N = 1674). Androgen levels were compared to those of age- and sex-matched controls (N = 59).

RESULTS

AAM but not pubertal stage or biochemical parameters related to depression. Girls with AAM at the lower normative range of pubertal development were 61 % more likely to develop depression and scored 4.9 points higher on the depression scale than girls experiencing menarche at the population average. Androstenedione levels were increased in the psychiatric sample, but neither androgen nor gonadal hormone levels were associated with depression severity.

LIMITATIONS

The study is cross-sectional.

CONCLUSIONS

These observations confirm previous studies in mostly subclinical depression and highlight the importance of AAM for adolescent depression. Thus, AAM could be considered a prognostic factor for a clinical risk score assessing the probability of adolescent depression. Moreover, these findings suggest fostering efforts that address risk factors that contribute to an earlier AAM.

Insomnia, sleep duration, and risk of anxiety: A two-sample Mendelian randomization study

BACKGROUND

The effect of insomnia and sleep duration on risk of anxiety has been assessed based on traditional epidemiological studies. However, the inconsistent conclusions do not establish causal associations. This study aimed to explore the causal associations of insomnia, short sleep, and long sleep with anxiety.

METHODS

We used summary statistics from three large-scale genome-wide association studies (GWAS) of European ancestry to perform a two-sample Mendelian randomization (MR) study. MR analyses were mainly conducted with the inverse-variance-weighted (IVW) method. To evaluate the robustness of our findings, we performed the weighted-median approach, the MR-Egger method, and the MR-robust adjusted profile score (MR-RAPS) method for sensitivity analyses.

RESULTS

There was a statistically significant association of genetically predicted insomnia with anxiety using the IVW method (OR = 1.36, 95% CI = 1.23-1.51, P < 0.001). Genetically predicted short sleep was potentially associated with anxiety using IVW method (OR = 1.67, 95% CI = 1.08-2.60, P = 0.022). However, sensitivity analyses did not find the causal association of short sleep with anxiety (all P > 0.053). We did not observe a statistically significant causal association of genetically predicted long sleep with anxiety (OR = 0.91, 95% CI = 0.48-1.74, P = 0.775).

CONCLUSIONS

We found strong evidence that insomnia but not short sleep and long sleep has a causal effect on anxiety. The characteristics of insomnia should be incorporated into anxiety prevention and intervention strategies, which have important public health significance.

Mediators of the association between educational attainment and type 2 diabetes mellitus: a two-step multivariable Mendelian randomisation study

AIMS/HYPOTHESIS

Type 2 diabetes mellitus is a major health burden disproportionately affecting those with lower educational attainment (EA). We aimed to obtain causal estimates of the association between EA and type 2 diabetes and to quantify mediating effects of known modifiable risk factors.

METHODS

We applied two-step, two-sample multivariable Mendelian randomisation (MR) techniques using SNPs as genetic instruments for exposure and mediators, thereby minimising bias due to confounding and reverse causation. We leveraged summary data on genome-wide association studies for EA, proposed mediators (i.e. BMI, blood pressure, smoking, television watching) and type 2 diabetes. The total effect of EA on type 2 diabetes was decomposed into a direct effect and indirect effects through multiple mediators. Additionally, traditional mediation analysis was performed in a subset of the National Health and Nutrition Examination Survey 2013-2014.

RESULTS

EA was inversely associated with type 2 diabetes (OR 0.53 for each 4.2 years of schooling; 95% CI 0.49, 0.56). Individually, the largest contributors were BMI (51.18% mediation; 95% CI 46.39%, 55.98%) and television watching (50.79% mediation; 95% CI 19.42%, 82.15%). Combined, the mediators explained 83.93% (95% CI 70.51%, 96.78%) of the EA-type 2 diabetes association. Traditional analysis yielded smaller effects but showed consistent direction and priority ranking of mediators.

CONCLUSIONS/INTERPRETATION

These results support a potentially causal protective effect of EA against type 2 diabetes, with considerable mediation by a number of modifiable risk factors. Interventions on these factors thus have the potential of substantially reducing the burden of type 2 diabetes attributable to low EA.

Causal Effect of Age at Menarche on the Risk for Depression: Results From a Two-Sample Multivariable Mendelian Randomization Study

A fair number of epidemiological studies suggest that age at menarche (AAM) is associated with depression, but the reported effect sizes are small, and there is evidence of residual confounding. Moreover, previous Mendelian randomization (MR) studies to avoid inferential problems inherent to epidemiological studies have provided mixed findings. To clarify the causal relationship between age at menarche and broadly defined depression risk, we used 360 genome-wide significantly AAM-related single-nucleotide polymorphisms (SNPs) as instrumental variable and data from the latest GWAS for the broadly defined depression risk on 807,553 individuals (246,363 cases and 561,190 controls). Multiple methods to account for heterogeneity of the instrumental variable (penalized weighted median, MR Lasso, and contamination mixture method), systematic and idiosyncratic pleiotropy (MR RAPS), and horizontal pleiotropy (MR PRESSO and multivariable MR using three methods) were used. Body mass index, education attainment, and total white blood count were considered pleiotropic phenotypes in the multivariable MR analysis. In the univariable [inverse-variance weighted (IVW): OR = 0.96, 95% confidence interval = 0.94–0.98, p = 0.0003] and multivariable MR analysis (IVW: OR = 0.96, 95% confidence interval = 0.94–0.99, p = 0.007), there was a significant causal effect of AAM on depression risk. Thus, the present study supports conclusions from previous epidemiological studies implicating AAM in depression without the pitfalls of residual confounding and reverse causation. Considering the adverse consequences of an earlier AAM on mental health, this finding should foster efforts to address risk factors that promote an earlier AAM.

Genetically predicted higher educational attainment decreases the risk of stroke: a multivariable Mendelian randomization study

Background

The causal association between educational attainment (EA) and stroke remains unclear. Hence, a novel multivariable Mendelian randomization (MVMR) approach was applied to solve this issue.

Methods

The single nucleotide polymorphisms (SNPs) from a recent genome-wide association study (GWAS) on years of schooling served as instruments. Univariable mendelian randomization (MR) and MVMR analyses were performed to detect the relationship between genetically predicted EA and the stroke risk. In the MVMR, cigarette consumption, alcohol consumption, body mass index (BMI), intelligence, and hypertension were adjusted. The summary statistics for stroke from the MEGASTROKE consortium included 446,696 participants (40,585 cases of stroke and 34,217 cases of ischemic stroke), most of whom were of European descent.

Results

In the univariable MR, genetically predicated EA could decrease the risks of total stroke (OR = 0.66, 95% CI 0.61–0.72, P = 2.70 × 10^–23), ischemic stroke (OR = 0.67, 95% CI 0.61–0.73, P = 2.58 × 10^–18), large artery atherosclerosis (OR = 0.51, 95% CI 0.40–0.64, P = 1.80 × 10^–8), small vessel stroke (OR = 0.60, 95% CI 0.49–0.73, P = 5.59 × 10^–7), and cardioembolic stroke (OR = 0.81, 95% CI 0.68–0.96, P = 1.46 × 10^–2) using the inverse-variance weighted (IVW) estimator. Higher EA might be negatively correlated with the odds of total stroke (OR = 0.62, 95% CI 0.50–0.77, P = 1.44 × 10^–5), ischemic stroke (OR = 0.63, 95% CI 0.50–0.80, P = 1.41 × 10^–4), and cardioembolic stroke (OR = 0.59, 95% CI 0.39–0.90, P = 0.01), but was not significant in large artery atherosclerosis (OR = 0.65, 95% CI 0.37–1.15, P = 0.14) and small vessel stroke (OR = 0.68, 95% CI 0.41–1.13, P = 0.14) after controlling other exposures.

Conclusions

We found that genetically predicated higher EA decreased the risks of total stroke, ischemic stroke, and cardioembolic stroke, independent of smoking, alcohol consumption, BMI, intelligence, and hypertension.

Educational attainment and mortality in schizophrenia

BACKGROUND

Individuals suffering from schizophrenia have a reduced life expectancy with cardiovascular disease (CVD) as a major contributor. Low educational attainment is associated with schizophrenia, as well as with all-cause and CVD mortality. However, it is unknown to what extent low educational attainment can explain the increased mortality in individuals with schizophrenia.

AIM

Here, we quantify associations between educational attainment and all-cause and CVD mortality in individuals with schizophrenia, and compare them with the corresponding associations in the general population.

METHOD

All Norwegian citizens born between January 1, 1925, and December 31, 1959, were followed up from January 1, 1990, to December 31, 2014. The total sample included 1,852,113 individuals, of which 6548 were registered with schizophrenia. We estimated hazard ratios (HR) for all-cause and CVD mortality with Cox models, in addition to life years lost. Educational attainment for index persons and their parents were included in the models.

RESULTS

In the general population individuals with low educational attainment had higher risk of all-cause (HR: 1.48 [95% CI: 1.47-1.49]) and CVD (HR: 1.59 [95% CI: 1.57-1.61]) mortality. In individuals with schizophrenia these estimates were substantially lower (all-cause: HR: 1.13 [95% CI: 1.05-1.21] and CVD: HR: 1.12 [95% CI: 0.98-1.27]). Low educational attainment accounted for 3.28 (3.21-3.35) life years lost in males and 2.48 (2.42-2.55) years in females in the general population, but was not significantly associated with life years lost in individuals with schizophrenia. Results were similar for parental educational attainment.

CONCLUSIONS

Our results indicate that while individuals with schizophrenia in general have lower educational attainment and higher mortality rates compared with the general population, the association between educational attainment and mortality is smaller in schizophrenia subjects than in the general population.

Risk factors for community-acquired pneumonia among inpatients with mental disorders in a tertiary general hospital

INTRODUCTION

Community-acquired pneumonia (CAP) is an important cause of hospitalization and death in patients with mental disorders. It is critical to understand the risk factors of CAP and determine prevention strategies to reduce CAP. The aim of this study is to explore the characteristics of inpatients with mental disorders who have CAP and analyze the risk factors.

METHODS

This retrospective study included 16,934 inpatients with mental disorders who were admitted for the first time to a tertiary general hospital between January 2017 and July 2021 (excluding January 2020-May 2020). Risk factors for CAP were identified by logistic regression analysis after propensity score matching (PSM, 1:4) for age, gender, and BMI.

RESULTS

The CAP rate of inpatients with mental disorders was 1.78%. Inpatients who had CAP had a significantly prolonged hospital stay, and were more often admitted to a closed ward or the ICU. After PSM, the multivariable analysis revealed that clozapine use (OR = 3.212, 95% CI = 1.744-5.915, P < 0.001), schizophrenia spectrum disorder (OR = 2.785, 95% CI = 1.684-4.607, P < 0.001), alcohol consumption (OR = 2.549, 95% CI = 1.586-4.096, P < 0.001), cardiovascular disease (OR = 2.299, 95% CI = 1.362-3.879, P = 0.002), Charlson comorbidity index (CCI) ≥ 3 (OR = 2.092, 95% CI = 1.342-3.260, P = 0.001), organic mental disorder (OR = 1.941, 95% CI = 1.194-3.156, P = 0.007), antipsychotic drug use (OR = 1.886, 95% CI = 1.312-2.711, P = 0.001), unmarried status (OR = 1.720, 95% CI = 1.164-2.541, P = 0.006) and junior high school education (OR = 1.591, 95%CI = 1.010-2.508, P = 0.045) were independent risk factors for CAP in inpatients with mental disorders.

CONCLUSION

CAP was common in inpatients with mental disorders. Patients with mental disorders have unique risk factors for CAP. Further research is required to explore the relationship and mechanism between different mental disorders, antipsychotic drugs and CAP.

Estimating causal effects of genetically predicted type 2 diabetes on COVID-19 in the East Asian population

BACKGROUND

Observational studies suggested that type 2 diabetes mellitus (T2DM) was associated with an increased risk of coronavirus disease 2019 (COVID-19). However, Mendelian randomization (MR) studies in the European population failed to find causal associations, partly because T2DM was pleiotropically associated with body mass index (BMI). We aimed to estimate the causal effects of T2DM on COVID-19 outcomes in the East Asian (EAS) population using a two-sample MR approach.

METHODS

We obtained summary statistics from a genome-wide association study (GWAS) that included 433,540 EAS participants as the exposure dataset for T2DM risk and from COVID-19 Host Genetics Initiative GWAS meta-analyses (round 7) of EAS ancestry as the outcome dataset for COVID-19 susceptibility (4,459 cases and 36,121 controls), hospitalization (2,882 cases and 31,200 controls), and severity (794 cases and 4,862 controls). As the main MR analysis, we performed the inverse variance weighted (IVW) method. Moreover, we conducted a series of sensitivity analyses, including IVW multivariable MR using summary statistics for BMI from a GWAS with 158,284 Japanese individuals as a covariate.

RESULTS

The IVW method showed that the risk of T2DM significantly increased the risk of COVID-19 susceptibility (odds ratio [OR] per log (OR) increase in T2DM, 1.11; 95% confidence interval [CI], 1.02-1.20; P = 0.014) and hospitalization (OR, 1.15; 95% CI, 1.04-1.26; P = 0.005), although the risk of severity was only suggestive. Moreover, IVW multivariable MR analysis indicated that the causal effects of T2DM on COVID-19 outcomes were independent of the effect of BMI.

CONCLUSIONS

Our MR study indicated for the first time that genetically predicted T2DM is a risk factor for SARS-CoV-2 infection and hospitalized COVID-19 independent of obesity in the EAS population.

Identifying causality, genetic correlation, priority and pathways of large-scale complex exposures of breast and ovarian cancers

BACKGROUND

Genetic correlations, causalities and pathways between large-scale complex exposures and ovarian and breast cancers need systematic exploration.

METHODS

Mendelian randomisation (MR) and genetic correlation (GC) were used to identify causal biomarkers from 95 cancer-related exposures for risk of breast cancer [BC: oestrogen receptor-positive (ER + BC) and oestrogen receptor-negative (ER - BC) subtypes] and ovarian cancer [OC: high-grade serous (HGSOC), low-grade serous, invasive mucinous (IMOC), endometrioid (EOC) and clear cell (CCOC) subtypes].

RESULTS

Of 31 identified robust risk factors, 16 were new causal biomarkers for BC and OC. Body mass index (BMI), body fat mass (BFM), comparative body size at age 10 (CBS-10), waist circumference (WC) and education attainment were shared risk factors for overall BC and OC. Childhood obesity, BMI, CBS-10, WC, schizophrenia and age at menopause were significantly associated with ER + BC and ER - BC. Omega-6:omega-3 fatty acids, body fat-free mass and basal metabolic rate were positively associated with CCOC and EOC; BFM, linoleic acid, omega-6 fatty acids, CBS-10 and birth weight were significantly associated with IMOC; and body fat percentage, BFM and adiponectin were significantly associated with HGSOC. Both GC and MR identified 13 shared factors. Factors were stratified into five priority levels, and visual causal networks were constructed for future interventions.

CONCLUSIONS

With analysis of large-scale exposures for breast and ovarian cancers, causalities, genetic correlations, shared or specific factors, risk factor priority and causal pathways and networks were identified.

Loneliness and Mental Health: The Mediating Effect of Perceived Social Support

Social connectedness is a fundamental human need. The Evolutionary Theory of Loneliness (ETL) predicts that a lack of social connectedness has long-term mental and physical health consequences. Social support is a potential mechanism through which loneliness influences health. The present cross-sectional study examined the relationship between loneliness and mental health, and the mediating effects of social support in a Dutch adult sample (N = 187, age 20 to 70). The health variables included in the study are anxiety, depression, somatic symptoms as measured by the SCL-90, and the DSM-5 diagnosis somatic symptom disorder. The results indicated that social support partially mediated the relationship between loneliness and anxiety, depression, and somatic symptoms. These results indicate that social support partially explains the relationship between loneliness and physical and mental health issues. The relationship between loneliness and being diagnosed with somatic symptom disorder was not mediated by social support. This suggests that the mechanisms through which loneliness relates to either somatic symptoms or somatic symptom disorder are different.

Causal relationship between educational attainment and the risk of rheumatoid arthritis: a Mendelian randomization study

Background

Educational attainment is moderately heritable and inversely associated with the risk of rheumatoid arthritis. However, the causality from educational attainment on rheumatoid arthritis remained unknown. Here, we aimed to determine whether educational attainment is causally associated with rheumatoid arthritis (RA) by using Mendelian randomization (MR) approach.

Methods

Summary statistics data for RA were obtained from an available, published meta-analysis of genome-wide association studies (GWAS) that included 14,361 RA cases and 43,923 controls of European ancestry. The instrumental variables for educational attainment were obtained from a GWAS meta-analysis that included over 1 million individuals (N = 1,131,881) of European ancestry. MR analyses were mainly performed using the inverse-variance weighted (IVW) method. Sensitivity analyses were further performed to test the robustness of the association using the weighted median method, MR-Egger, Cochran Q test, “leave-one-out” analysis and MR-PRESSO test.

Results

A total of 387 SNPs were employed as instrumental variables in our MR analysis. Genetically predicted higher educational attainment was associated with a significantly lower risk of RA using the IVW method (odds ratio [OR] = 0.42, 95% confidence interval [CI]: 0.34–0.52; p = 1.78 × 10^− 14). The weighted median method and MR Egger regression analysis yielded consistent results. The effect estimate remained robust after the outlier variants and SNPs (associated with the confounding factors) were excluded. “Leave-one-out” analysis confirmed the stability of our results. Additionally, the results suggested the absence of the horizontal pleiotropy.

Conclusions

The MR analysis supported a potential inverse causative relationship between educational attainment and the risk of RA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41927-021-00216-0.

Causal risk and protective factors in rheumatoid arthritis: A genetic update

The characterization of risk and protective factors in complex diseases such as rheumatoid arthritis (RA) has evolved from epidemiological studies, which test association, to the use of Mendelian randomization approaches, which test direct relationships. Indeed, direct associations with the mucosal origin of RA are retrieved with periodontal disease (Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans predominantly), interstitial lung involvement, tobacco smoking and air pollutants. Next, factors directly associated with an acquired immune response include genetic factors (HLA DRB1, PTPN22), capacity to produce anti-modified protein antibodies (AMPA), and relatives with a history of autoimmune diseases. Finally, factors can be also classified according to their direct capacity to interfere with the IL-6/CRP/sIL-IL6R proinflammatory pathway as risk factor (body fat, cardiometabolic factors, type 2 diabetes, depressive syndrome) or either as protective factors by controlling of sIL-6R levels (higher education level, and intelligence). Although some co-founders have been characterized (e.g. vitamin D, physical activity, cancer) the direct association with sex-discrepancy, pregnancy, and infections among other factors remains to be better explored.