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

Causality Between ADHD, ASD, and CVDs: A Two-Step, Two-Sample Mendelian Randomization Investigation

BACKGROUND

While observational studies have established a connection between attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and heightened risk for cardiovascular diseases (CVD), the causal relationships are not well-defined. This study is designed to examine the causality between ASD, ADHD, and CVD risk as well as investigate the mediating factors through which ADHD and ASD influence CVD.

METHODS AND RESULTS

Leveraging two-sample Mendelian randomization (MR) approaches and large scale GWAS summary stats, we examined underlying causal links between ASD and ADHD and the risk of CVDs. The analysis indicated that ADHD was related to an increased likelihood of developing coronary heart disease (OR [95% CI] 1.12 [1.03, 1.21], p = .008), heart failure (OR [95% CI] 1.14 [1.07, 1.22], p = 1.45 × 10-4), and large-artery stroke (OR [95% CI] 1.35 [1.09, 1.66], p = .005). In parallel, ASD showed a correlation with a greater atrial fibrillation risk (OR [95% CI] 1.09 [1.03, 1.16], p = .005] and heart failure (OR [95% CI] 1.11 [1.04, 1.19], p = .004). Additionally, we explored the mediating role of CVD risk factors through two-step MR and multivariable MR, highlighting the possible role of smoking, prescription opioid use, triglycerides, education, income, Townsend deprivation index, and obesity in the causal association of ADHD, ASD, on CVDs.

CONCLUSION

This MR study highlights the necessity for rigorous cardiovascular surveillance and interventions to decrease adverse cardiovascular events in people with ADHD or ASD by preventing identified mediating risk factors.

Genetic Study of Psoriasis Highlights its Close Link with Socioeconomic Status and Affective Symptoms

Psoriasis is an inflammatory skin disease with an estimated heritability of around 70%. Previous GWASs have detected several risk loci for psoriasis. To further improve the understanding of the genetic risk factors impacting the disease, we conducted a discovery GWAS in FinnGen and a subsequent replication and meta-analysis with data from the Estonian Biobank and the UK Biobank; the study sample included 925,649 individuals (22,659 cases and 902,990 controls), the largest sample for psoriasis yet. In addition, we conducted downstream analyses to find out more about psoriasis' cross-trait genetic correlations and causal relationships. We report 6 risk loci, which, to our knowledge, are previously unreported, most of which harbor genes related to NF-κB signaling pathway and overall immunity. Genetic correlations highlight the relationship between psoriasis and smoking, higher body weight, and lower education level. In addition, we report causal relationships between psoriasis and mood symptoms as well as 2-directioned causal relationship between psoriasis and lower education level. Our results provide further knowledge on psoriasis risk factors, which may be useful in the development of future treatment strategies.

The association between overweight and varying degrees of obesity with subjective well-being and depressive symptoms: A two sample Mendelian randomization study

OBJECTIVE

This study utilized the Mendelian randomization (MR) method to elucidate the causal relationship between genetically predicted overweight and various degrees of obesity with depressive symptoms and subjective well-being (SWB).

METHODS

Pooled genome-wide association studies (GWAS) data for overweight (BMI ≥ 25 kg/m2), class 1 obesity (BMI ≥ 30 kg/m2), and class 2 obesity (BMI ≥ 35 kg/m2) were used as exposures. Summary GWAS data for depressive symptoms and SWB were used as outcomes. Multiple MR methods, primarily inverse-variance weighted (IVW), were applied, and sensitivity analyses were conducted to assess heterogeneity and pleiotropy.

RESULTS

The MR analysis provided evidence that genetically predicted overweight(IVW β = 0.033; 95 %CI 0.008-0.057; P = 0.010) and class 1 obesity(IVW β = -0.033; 95 %CI -0.047 - -0.020; P < 0.001) were causally associated with increased depressive symptoms. Genetically predicted class 2 obesity(IVW β = 1.428; 95 %CI 1.193-1.710; P < 0.001) were associated with reduced SWB. There was no strong evidence of a causal association between genetically predicted overweight and class 1 obesity with SWB. Similarly, genetically predicted class 2 and class 3 obesity did not show strong evidence of a causal association with depressive symptoms. Sensitivity analysis revealed relationships of a similar magnitude.

CONCLUSION

This genetically informed MR study suggests that Overweight and class 1 obesity may causally increased depressive symptoms but not decrease SWB. In contrast, class 2 obesity may causally decrease SWB but not increase depressive symptoms.

Mental health from childhood to adolescence predicts excessive weight and body composition at 18 years

OBJECTIVE

To investigate the association of mental health in childhood and adolescence with four outcomes at 18 years: ultra-processed food (UPF) consumption, body mass index (BMI), excessive weight (EW), and body composition, including fat mass (FM) and fat free mass (FFM) in kg, FM index (FMI) and FFM index (FFMI) in kg/m2.

METHODS

Cohort study in which The Development and Well-Being Assessment (DAWBA) (6 and 11 years) and the MINI International Neuropsychiatric Interview (MINI) (18 years) provided information on internalizing (INT), externalizing (EXT) and any mental disorder (ANY). The exposure was classified in: "never", "at 6 and/or 11 years", "at 18 years only" and "at 6, 11, and 18 years". Linear and logistic regression were run. All analyses were stratified by sex.

RESULTS

A total of 2722 participants were analyzed. At 18 years, female with EXT disorders at 6 and/or 11 years presented higher BMI (β: 1.70; 0.18-3.23), FM (β: 4.74; 1.42-8.06), and FMI (β: 1.53; 0.28-2.79) than those who never had. The odds of EW at 18 years was also higher in females with EXT disorders at 6 and/or 11 years (OR: 3.39; 1.56-7.36) and at the three time points (OR: 7.08; 1.69-29.59). Males with EXT disorders at 6 and/or 11 years presented higher FM (β: 4.45; 1.85-7.06) and FMI (β: 1.47; 0.63-2.31).

CONCLUSIONS

Among children and adolescents showing symptoms of EXT disorders, weight should be monitored carefully, thus ultimately contributing to reduce the burden of EW in adolescence.

Association between air pollutants and four major mental disorders: Evidence from a Mendelian randomization study

BACKGROUND

Existing epidemiological studies have indicated a correlation between air pollutants and the occurrence of mental disorders. However, it is difficult to estimate the causal relationship between the two because of the limitations of traditional epidemiological research. In our study, we aimed to extensively explore the causal relationship between five types of air pollutants and four types of mental disorders.

METHODS

Based on the IEU OPEN GWAS database, we performed a two-sample MR analysis. The primary analysis method utilized was the inverse variance weighted (IVW) method, supplemented by the MR-Egger method and the weighted median method. Additionally, we conducted sensitivity analyses with the Cochran's Q statistic method, the leave-one-out method, and the MR-Egger intercept. We chose at least 4 GWAS datasets for each of the four psychiatric diseases and conducted a meta-analysis of our results of the MR analysis.

RESULTS

The meta-analysis's findings demonstrated a causal link between depression and PM2.5 (OR=1.020, 95 %CI: (1.010,1.030), P=0.001). PM10 and schizophrenia are also causally related (OR=1.136, 95 %CI: (1.034,1.248), P=0.008). Nitrogen oxides and bipolar disorder have a causal relationship (OR=1.002, 95 %CI: (1.000,1.003), P=0.022). Nitrogen oxides and schizophrenia have a high causal association (OR=1.439, 95 %CI: (1.183,1.752), P<0.001).

CONCLUSION

This study observed a causal association between increased concentrations of PM2.5, PM10, and nitrogen oxides and the occurrence of depression, schizophrenia, and bipolar disorder. Our research findings have certain guiding implications for treating and preventing mental disorders.

Sex differences in shared genetic determinants between severe mental disorders and metabolic traits

High rates of metabolic risk factors contribute to premature mortality in patients with severe mental disorders, but the molecular underpinnings of this association are largely unknown. We performed the first analysis on shared genetic factors between severe mental disorders and metabolic traits considering the effect of sex. We applied an integrated analytical pipeline on the largest sex-stratified genome-wide association datasets available for bipolar disorder (BD), major depressive disorder (MDD), schizophrenia (SZ), and for body mass index (BMI) and waist-to-hip ratio (WHR) (all including participants of European origin). We observed extensive genetic overlap between all severe mental disorders and variants associated with BMI in women or men and identified several genetic loci shared between BD, or SZ and BMI in women (24 and 91, respectively) or men (13 and 208, respectively), with mixed directions of effect. A large part of the identified genetic variants showed sex differences in terms of location, genes modulated in adipose tissue and/or brain regions, and druggable targets. By providing a complete picture of disorder specific and cross-disorder shared genetic determinants, our results highlight potential sex differences in the genetic liability to metabolic comorbidities in patients with severe mental disorders.

Evaluating the distinct effects of body mass index at childhood and adulthood on adult major psychiatric disorders

Children with high body mass index (BMI) are at heightened risk of developing health issues in adulthood, yet the causality between childhood BMI and adult psychiatric disorders remains unclear. Using a life course Mendelian randomization (MR) framework, we investigated the causal effects of childhood and adulthood BMI on adult psychiatric disorders, including Alzheimer's disease, anxiety, major depressive disorder, obsessive-compulsive disorder (OCD), and schizophrenia, using data from the Psychiatric Genomics Consortium and FinnGen study. Childhood BMI was significantly associated with an increased risk of schizophrenia, while adulthood BMI was associated with a decreased risk of OCD and schizophrenia. Multivariable MR analyses indicated a direct causal effect of childhood BMI on schizophrenia, independent of adulthood BMI and lifestyle factors. No evidence of causal associations was found between childhood BMI and other psychiatric outcomes. The sensitivity analyses yielded broadly consistent findings. These findings highlight the critical importance of early-life interventions to mitigate the long-term consequences of childhood adiposity.

Childhood obesity and adolescent follow-up depressive symptoms: exploring a moderated mediation model of body esteem and gender

Obesity is a well-recognized risk factor for adolescent depressive symptoms, but mediating mechanisms of this association have scarcely been studied. This study is unique in examining an indirect pathway of this link via body esteem (BE) prospectively from childhood (8-12 years) to adolescence (13-18 years). In addition, potential gender moderation was examined. This study utilized data from a case-control study comparing 100 children with and without obesity matched on important confounders (age, gender, and socioeconomic status). Our findings provide support for the mediating role of BE in the link between childhood weight status and adolescent depressive symptoms at a 5-year follow-up. This mediation effect did not differ between boys and girls. The findings suggest the relevance of specifically targeting children's BE in preventive intervention programs among children with obesity to prevent future mental health problems.

Celiac disease and attention-deficit/hyperactivity disorder: a bidirectional Mendelian randomization analysis

Background

Recent observational research suggests a potential link between celiac disease (CeD) and an increased incidence of attention-deficit/hyperactivity disorder (ADHD). However, the genetic relationship between CeD and ADHD remains unclear. In order to assess the potential genetic causality between these two conditions, we conducted a Mendelian randomization (MR) analysis.

Methods

We performed a bidirectional MR analysis to investigate the relationship between CeD and ADHD. We carefully selected single nucleotide polymorphisms (SNPs) from publicly available large-scale genome-wide association studies (GWAS) databases, employing rigorous quality screening criteria. MR estimates were obtained using four different methods: fixed-effect inverse variance weighted (fe-IVW), random-effect inverse variance weighting (re-IVW), weighted median (WM), and MR-Egger. The robustness and reliability of our findings were confirmed through sensitivity analyses, assessment of instrumental variable (IV) strength (F-statistic), and statistical power calculations.

Results

Our MR analyses did not reveal any significant genetic associations between CeD and ADHD (fe-IVW: OR = 1.003, 95% CI = 0.932-1.079, P = 0.934). Similarly, in the reverse direction analysis, we found no evidence supporting a genetic relationship between ADHD and CeD (fe-IVW: OR = 0.850, 95% CI = 0.591-1.221, P = 0.378). Various MR approaches consistently yielded similar results. Sensitivity analysis indicated the absence of significant horizontal pleiotropy or heterogeneity. However, it's important to note that the limited statistical power of our study may have constrained the causal analysis of the exposure's influence on the outcome.

Conclusions

Our findings do not provide compelling evidence for a genetic association between CeD and ADHD within the European population. While the statistical power of our study was limited, future MR research could benefit from larger-scale datasets or datasets involving similar traits. To validate our results in real-world scenarios, further mechanistic studies, large-sample investigations, multicenter collaborations, and longitudinal studies are warranted.