Causal associations between psoriasis, eczema, urticaria, and mental illness: A bidirectional Mendelian randomization study of the European population.

Observational studies have reported a relationship between multiple common dermatoses and mental illness. To assess the potential bidirectional causality between 3 skin disorders (psoriasis, eczema, and urticaria) and 4 psychiatric disorders (bipolar disorder, schizophrenia, major depressive disorder, and anxiety) in the European population, we used Mendelian randomization (MR) analysis, which provides definitive evidence for causal inference. Eligible single nucleotide polymorphisms were screened for dermatological and psychiatric disorders using a genome-wide association study database. We conducted bidirectional, 2-sample MR analysis using instrumental variables related to psoriasis, eczema, and urticaria as exposure factors, and bipolar disorder, schizophrenia, major depression, and anxiety as outcomes. Reverse MR analysis with bipolar disorder, schizophrenia, major depression, and anxiety as exposure and psoriasis, eczema, and urticaria as outcomes were also performed, and the causality was analyzed using inverse-variance weighting (IVW), MR-Egger, and weighted median methods. To thoroughly assess causality, sensitivity analyses were conducted using the IVW, MR-PRESSO, and MR-Egger methods. The results showed that bipolar disorder increased the incidence of psoriasis (odds ratio = 1.271, 95% confidence interval = 1.003-1.612, P = .047), heterogeneity test with Cochran Q test in the IVW showed P value > .05, (P = .302), the MR-Pleiotropy and MR-PRESSO (outlier methods) in the multiplicity test showed P value > .05, (P = .694; P = .441), and MR-Pleiotropy evidence showed no apparent intercept (intercept = -0.060; SE = 0.139; P = .694). Major depression increased the risk of eczema (odds ratio = 1.002, 95% confidence interval = 1.000-1.004, P = .024), heterogeneity test showed P value > .05, (P = .328), multiplicity detection showed P value > .05, (P = .572; P = .340), and MR-Pleiotropy evidence showed no apparent intercept (intercept = -0.099; SE = 0.162; P = .572). Sensitivity analyses of the above results were reliable, and no heterogeneity or multiplicity was found. This study demonstrated a statistically significant causality between bipolar disorder and psoriasis, major depression, and eczema in a European population, which could provide important information for physicians in the clinical management of common skin conditions.

Mo N ，Yang Y ，Wang W ，Zhou P ，Liu F ，Zhang Y ，Zhang J ，Han L ，Lu C ... -  《-》

Evidence for a causal association between psoriasis and psychiatric disorders using a bidirectional Mendelian randomization analysis in up to 902,341 individuals.

The causal association between psoriasis and psychiatric disorders remains ambiguous. This study aimed to investigate the causal relationship between psoriasis and common psychiatric disorders using bidirectional Mendelian randomization (MR) analysis. Major depressive disorder (MDD) (N = 217,584), bipolar disorder (N = 51,710), schizophrenia (N = 77,096), and anxiety disorder (N = 218,792) were obtained as outcomes, and psoriasis (N = 337,159) were as exposure. Inverse variance weighting (IVW) was used as the main method, with other sensitivity methods as auxiliary methods. Sensitivity analysis and heterogeneity tests were performed to ensure the robustness of the results. We also performed a subgroup analysis of cases with psoriatic arthritis (PsA) (N = 213,879) by using the same testing methods. MR showed that the genetic risk of psoriasis was positively associated with bipolar disorder (odds ratio (OR) = 13.54, 95 % confidence interval (95%CI): 2.43-75.37, P = 0.002) and MDD (OR = 1.08, 95%CI: 1.01-1.15, P = 0.027), which indicated possible causal relationships between psoriasis and these two diseases. Schizophrenia (OR = 3.52, 95%CI: 0.22-55.71, P = 0.372) and anxiety disorders (OR = 0.65, 95%CI: 0.16-2.63, P = 0.546) indicated no significant causal association. No reverse causal effects of psychiatric disorders on psoriasis were found. Subgroup analysis also suggested causal association of PsA with the bipolar affective disorder (OR = 1.05, 95%CI: 1.01-1.08, P = 0.005). Potential pleiotropic effects, restriction to European populations, and differences in diagnostic criteria. This study has supported the causal association of psoriasis with MDD and bipolar disorder, and the subtype PsA with bipolar disorder, which informed the intervention for mental illnesses in patients with psoriasis.

Wang Y ，Wang X ，Gu X ，Pan J ，Ouyang Z ，Lin W ，Zhu W ，Wang M ，Su J ... -  《-》

Genetic correlation and causal associations between psychiatric disorders and lung cancer risk.

Patients with certain psychiatric disorders have increased lung cancer incidence. However, establishing a causal relationship through traditional epidemiological methods poses challenges. Available summary statistics of genome-wide association studies of cigarette smoking, lung cancer, and eight psychiatric disorders, including attention deficit/hyperactivity disorder (ADHD), autism, depression, major depressive disorder, bipolar disorder, insomnia, neuroticism, and schizophrenia (range N: 46,350-1,331,010) were leveraged to estimate genetic correlations using Linkage Disequilibrium Score Regression and assess causal effect of each psychiatric disorder on lung cancer using two-sample Mendelian randomization (MR) models, comprising inverse-variance weighted (IVW), weighted median, MR-Egger, pleiotropy residual sum and outlier testing (MR-PRESSO), and a constrained maximum likelihood approach (cML-MR). Significant positive correlations were observed between each psychiatric disorder and both smoking and lung cancer (all FDR < 0.05), except for the correlation between autism and lung cancer. Both univariable and the cML-MA MR analyses demonstrated that liability to schizophrenia, depression, ADHD, or insomnia was associated with an increased risk of overall lung cancer. Genetic liability to insomnia was linked specifically to squamous cell carcinoma (SCC), while genetic liability to ADHD was associated with an elevated risk of both SCC and small cell lung cancer (all P < 0.05). The later was further supported by multivariable MR analyses, which accounted for smoking. Participants were constrained to European ancestry populations. Causal estimates from binary psychiatric disorders may be biased. Our findings suggest appropriate management of several psychiatric disorders, particularly ADHD, may potentially reduce the risk of developing lung cancer.

Shi J ，Wen W ，Long J ，Gamazon ER ，Tao R ，Cai Q ... -  《-》

The causal relationship between gut microbiota and inflammatory dermatoses: a Mendelian randomization study.

Mao R ，Yu Q ，Li J 《Frontiers in Immunology》

Association between retinal nerve fiber layer thickness and psychiatric disorders: a mendelian randomization study.

Retinal nerve fiber layer thickness, as a new visual indicator that may help diagnose mental disorders, is gaining attention from researchers. However, the causal relationship between retinal nerve fiber layer thickness and mental disorders is still to be effectively proved. A bidirectional Two-sample Mendelian randomization analysis was utilized to analyse aggregated data from large-scale genome-wide association studies, we selected genetic loci for retinal nerve fiber layer thickness in independent retinal abnormalities and three prevalent psychiatric disorders (schizophrenia, depression, bipolar disorder) as instrumental variables. The Two-sample Mendelian randomization analysis was mainly performed by inverse variance weighting and weighted median method. The Cochran Q test and leave-one-out sensitivity were used to ensure the robustness of the results. The Mendelian random polymorphism residuals and outliers were used to detect single nucleotide polymorphism outliers, and MR-Egger intercept test was used to test single nucleotide polymorphism horizontal pleiotropy. IVW showed that retinal nerve fiber layer thickness was positively associated with schizophrenia (OR = 1.057, 95%CI: 1.000-1.117, P < 0.05), in the study of bipolar disorder, MR analysis also suggested a positive causal relationship between retinal nerve fiber layer thickness and bipolar disorder (OR = 1.025, 95%CI: 1.005-1.046, P < 0.05), which indicated possible causal relationships between retinal nerve fiber layer thickness and these two diseases. Depression (OR = 1.000143, 95%CI: 0.9992631-1.001024, P = 0.74) indicated no significant causal association. No reverse causal effects of psychiatric disorders on retinal nerve fiber layer thickness were found. A statistically significant causal relationship between retinal nerve fiber layer thickness and schizophrenia and bipolar disorder has been supported by genetic means, indicating RNFL has potential to aid in the diagnosis of schizophrenia and bipolar disorder.

Fuyi Q ，Xiang C ，Xinling Z ，Zeyi G ，Liu Y ，Jia W ，Qing L ，Zhaowei T ，Yong Z ... -  《BMC Psychiatry》