Investigating the causal relationship between allergic disease and mental health

Challenges in interpreting Mendelian randomization studies with a disease as the exposure: Using COVID-19 liability studies as an exemplar

Mendelian randomization (MR) studies using diseases as exposures are increasingly prevalent although any observed associations do not necessarily imply effect of diseases. To illustrate this challenge, we conducted a systematic review of MR studies focusing on COVID-19 consequence. We hypothesized if outcome genome-wide association studies (GWAS) were conducted before COVID-19 pandemic in late 2019, any observed associations in these studies were unlikely to be driven by COVID-19. We systematically searched PubMed, EMBASE, and MEDLINE for all MR studies published between 1 January 2019 and 20 May 2023. Inclusion criteria included MR studies which used COVID-19 as the exposure and designed to assess COVID-19's impact on health outcomes. We extracted relevant information, such as result interpretation and relevance assumption assessment. This review was registered at PROSPERO (CRD42023421079). Amongst 57 included studies, 45 studies used outcome GWAS published prior to 2019 whilst the remaining studies likely used outcome GWAS containing data collected before 2019. Relevance assumption was assessed mainly by p values. A total of 35 studies showed an association of COVID-19 liability with health outcomes. Regardless of the results, 45 studies attributed these as evidence (or lack of evidence) of COVID-19 consequence. In MR studies using disease liability as exposure, relevance assumption should consider the prevalence of the disease in the outcome GWAS in the context of 2 sample Mendelian randomization study rather than p values/F-statistic alone. Even when these are verified, these studies likely suffered from pleiotropy, making corresponding interpretation as effect of disease challenging.

Type 2 inflammation: a Portuguese consensus using Web-Delphi and decision conferencing (INFLAT2-PT)

OBJECTIVES

Atopic/allergic diseases impose a growing burden on public health, affecting millions of patients worldwide. The main objective of this study was to develop a national expert consensus on relevant clinical questions related to type 2 inflammation.

METHODS

We conducted: a comprehensive literature review with a qualitative analysis to identify the most repeated themes on the overlap of conditions; a modified 3-round Web-Delphi (or e-Delphi); and a final online decision conference.

RESULTS

We included 51 studies. Following three Web-Delphi rounds, we ended up with 30 statements with a 76% overall full agreement rate, 16% agreement, 2% disagreement, and 0% full disagreement. The decision conference enabled adjustments, and the expert panel agreed unanimously on the final set of statements. The consensus used evidence synthesis, Web-Delphi, and decision conference to produce 30 statements on type 2 inflammation as a driver for multimorbidity in asthma, certain rhinitis phenotypes, atopic dermatitis, chronic rhinosinusitis with nasal polyps, and eosinophilic esophagitis grouped under five domains in underlying pathophysiology, multimorbidity, diagnosis and management, multidisciplinary management, and impact on mental health.

CONCLUSION

We expect the first Portuguese expert consensus INFLAT2-PT to promote understanding of type 2 inflammation diseases, multidisciplinary care, integrated care pathways, future research, and inform health authorities.

Association between allergic diseases and mental health conditions: An umbrella review

BACKGROUND

The mental health conditions of allergic diseases have been investigated, but the consistency and magnitude of their effects are unclear. The aim of this umbrella review was to systematically evaluate the published evidence on allergic diseases and mental health conditions to establish a new hierarchy of evidence and identify gaps in this area of research.

METHODS

We systematically searched PubMed, Embase, Web of Science, and the Cochrane Database of Systematic Reviews from database inception to April 30, 2024. We included systematic reviews that conducted meta-analyses that examined the association of allergic diseases and mental health conditions. We calculated summary effect estimates (odds ratios), 95% confidence intervals, I2 statistics, 95% prediction intervals, small study effects, and excess significance biases. We used AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews 2) to appraise the methodologic quality of the included studies.

RESULTS

We identified 21 eligible articles, which yielded 37 associations (348,405,029 total population) of allergic diseases and mental health conditions. The credibility of evidence was convincing (class I) for asthma and risk of attention-deficit/hyperactivity disorder (odds ratio 1.34, 95% confidence interval 1.24-1.44); and highly suggestive (class II) for allergic rhinitis and risk of tic disorders (2.61, 1.90-3.57), allergic rhinitis and risk of sleep disorders (2.17, 1.87-2.53), food allergy and risk of autism spectrum disorder (2.79, 2.08-3.75), atopic dermatitis and risk of depression (1.60, 1.43-1.79), atopic dermatitis and risk of anxiety (1.62 1.42-1.85), atopic dermatitis and risk of attention-deficit/hyperactivity disorder (1.28, 1.18-1.40), atopic dermatitis and risk of suicidal ideation (1.44, 1.25-1.65), asthma and risk of depression (1.64, 1.50-1.78), asthma and risk of anxiety (1.95, 1.68-2.26), asthma and risk of tic disorders (1.90, 1.57-2.30), asthma and risk of suicidal ideation (1.52, 1.37-1.70), and asthma and risk of suicide attempts (1.60, 1.33-1.92).

CONCLUSIONS

Allergic diseases are associated with increased risk of a range of mental health conditions, with the most convincing evidence for asthma. However, these associations do not imply causality, and there is large heterogeneity in these associations, which requires high-quality primary studies to identify causality and strength of evidence.

Dissecting the association of genetically predicted neuroticism with pre-eclampsia: A 2-sample Mendelian randomization study

Previous observational clinical studies have found a causal relationship between neurotic personality traits and various disorders. However, the relationship between neurotic personality characteristics and pre-eclampsia (PE) is not unclear. Two-sample Mendelian randomization (MR) was employed to examine the influence of neurotic personality traits on the risk of PE. From the Finnish genome-wide database, we identified 32 single-nucleotide polymorphisms linked to neuroticism personality traits, excluding 7 confounding variables related to blood pressure and BMI. The number of tool variables associated with PE was 25. Causality was assessed using inverse variance weighting, weighted median, MR-Egger, and weighted model methods. Sensitivity analyses, such as Cochran's Q statistic, MR-Egger intercept, MR pleiotropy residual sum and outlier, and leave-one-out analysis, were conducted to identify potential heterogeneity and horizontal pleiotropy. The present 2-sample MR study did not reveal any genetic associations between neuroticism and PE. A 2-sample Mendelian randomization analysis of 12 dichotomous neuroticism items indicated that genetic predisposition to worrying elevates the risk of PE. The inverse variance weighted method produced an odds ratio (OR) of 2.23 (95% CI: 1.36-3.65, P < .05), while the weighted median analysis indicated an OR of 2.41 (95% CI: 1.20-4.85, P < .05). However, there were no significant correlations between the MR Egger and weighted modes. This study found no genetic causal link between neuroticism and PE; however, carriers may have a genetically increased risk of PE, offering a more reliable foundation for future prevention efforts.

The Impact of Seasonality on Mental Health Disorders: A Narrative Review and Extension of the Immunoseasonal Theory

The impact of weather on mental illness is widely debated, but the mechanism of this relationship remains unclear. The immunoseasonal theory suggests that in winter, a T-helper 1 (Th1) response predominates, impairing Prefrontal Cortex (PFC) control, which exacerbates symptoms of depression, while after it, in summer, a Th2 response predominates in immunologically prone individuals, activating cortical and mesolimbic centers, which can exacerbate symptoms of psychosis. In this paper, we aim to describe the validity of this theory through a narrative review of data related to weather and immunology in psychiatry. This review extends existing literature by integrating immunological findings with psychiatric seasonality research, offering a mechanistic perspective that links Th1/Th2 shifts to specific symptom exacerbations. Winter Th1 severity may worsen depression and anxiety, while summer Th2 dominance appears to be associated with exacerbations of schizophrenia, mania, impulsivity, and suicide risk. It is possible that the mechanism of Th1 response potentiation and deterioration of PFC function is common to most psychiatric entities and is nonspecific. This suggests that seasonal immune dysregulation may play a broader role in psychiatric disorders than previously recognized, challenging the idea that seasonality impacts only selected conditions. Characteristic dysfunctions within an individual determine further differences in clinical manifestations. The mechanism of Th2 potentiation may not be limited to mania and psychosis but may also be associated with increased impulsivity and suicide risk. If the immunoseasonal theory is confirmed, selected immunological markers could be used not only in the diagnosis of psychiatric exacerbations but also in predicting symptom fluctuations and tailoring treatment strategies. This could enable more personalized interventions, such as seasonally adjusted medication dosing or targeted anti-inflammatory therapies. While this mechanism seems plausible, further research, especially analyzing markers of inflammatory and anti-inflammatory responses, is needed to better understand and confirm it.

Childhood allergy and anxiety/depression in early adulthood: A longitudinal study in the ALSPAC birth cohort

BACKGROUND

Allergic disease and common mental disorders frequently co-occur. However, little is known about the longitudinal impact of childhood allergy on the subsequent risk of developing anxiety or depression, and the possible biological mechanisms for this.

METHODS

We performed longitudinal analyses of data from the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort. The baseline sample comprised n = 5256 children with allergy data available at age 7yrs. We used multivariable regression to test associations between childhood allergy at age 7yrs and: a) four inflammatory markers at age 9yrs; b) depression and anxiety measures between ages 10-24yrs. Allergy measures included biological markers (total serum immunoglobulin E (tIgE), number of positive skin prick tests (SPTs)), and presence of eczema, asthma and/or food allergy (mother reported). Inflammatory markers were interleukin-6 (IL-6), C-reactive protein (CRP), IL-4 and IL-13. We used structural equation modelling to test whether inflammatory markers mediated the association between tIgE and depression/anxiety.

RESULTS

tIgE and having ≥ 1 positive SPT at age 7 were associated with IL-6 levels at age 9 (adjusted β = 0.09; 95 % CI 0.06-0.13; p < 0.001 and adjusted β = 0.06; 95 % CI 0.03-0.09; p < 0.001 respectively), but not with CRP, IL-4 or IL13 levels. We found no strong evidence of an association between childhood allergy and subsequent depression/anxiety during adolescence and early adulthood. This finding was consistent across biological and mother-reported allergy measures.

CONCLUSIONS

Biological markers of childhood allergy are associated with IL-6, a key inflammatory cytokine. However, childhood allergy may not have a large long-term effect on subsequent depression/anxiety.

Food Allergy and Mental Health in Children and Adolescents-The Role of Shared Familial Environment

BACKGROUND

Evidence suggests a link between food allergy and poor mental health, however, this may be explained by shared genetic and environmental factors. We aimed to investigate the association between food allergy of different severity and mental health in children, and the role of familial factors.

METHODS

This population-based, longitudinal cohort study is based on the Child and Adolescent Twin Study in Sweden with questionnaire data reported by parents and/or children. Food allergy 'ever' and doctor's diagnosis were reported at age 9-12 years, and ≥ 1 recent dispensation of adrenaline was used as a marker for current severe food allergy. Outcomes were identified using validated questionnaires for anxiety; Screen for Child Anxiety Related Disorders (SCARED); Strength and Difficulties Questionnaire (SDQ) and depression; Short Mood and Feelings Questionnaire (SMFQ), Center for Epidemiological Studies Depression Scale (CES-D) and Diagnostic and Statistical manual of Mental Disorders (DSM-IV-MDE) and reported at 9-12, 15 and 18 years of age. Multivariate linear and logistic modelling was applied to the whole cohort and a co-twin control approach to remove confounding by familial factors.

RESULTS

In total, 3039 (8.9%) children had a parent-reported food allergy. Among these, 1292 (43.5%) had non-severe food allergy without diagnosis, 1490 (49%) had non-severe food allergy with diagnosis and 257 (8.5%) had severe food allergy. Compared to children with no food allergy, non-severe food allergy with diagnosis by 9-12 years was associated with parent-reported anxiety/depression; SCARED (adjOR 2.10, 95% CI 1.48-2.98), SMFQ (adjOR 1.92, 95% CI 1.19-3.10) at 9-12 years and SDQ (adjβ 0.2, 95% CI 0.0-0.4) at 15 years. All other associations were null including for those with severe food allergy. All positive estimates in the full cohort were attenuated using co-twin controls.

CONCLUSION

Evidence associating paediatric food allergy severity and poor mental health was weak, and positive associations observed were likely due to familial confounding.

Allergic Diseases and Mental Health

Neuropsychiatric symptoms have long been acknowledged as a common comorbidity for individuals with allergic diseases. The proposed mechanisms for this relationship vary by disease and patient population and may include neuroinflammation and/or the consequent social implications of disease symptoms and management. We review connections between mental health and allergic rhinitis, atopic dermatitis, asthma, vocal cord dysfunction, urticaria, and food allergy. Many uncertainties remain and warrant further research, particularly with regard to how medications interact with pathophysiologic mechanisms of allergic disease in the neuroimmune axis. Proactive screening for mental health challenges, using tools such as the Patient Health Questionnaire and Generalized Anxiety Disorder screening instruments among others, can aid clinicians in identifying patients who may need further psychiatric evaluation and support. Although convenient, symptom screening tools are limited by variable sensitivity and specificity and therefore require healthcare professionals to remain vigilant for other mental health "red flags." Ultimately, understanding the connection between allergic disease and mental health empowers clinicians to both anticipate and serve the diverse physical and mental health needs of their patient populations.

Mendelian Randomization Studies in Atopic Dermatitis: A Systematic Review

Prior studies have found associations between atopic dermatitis (AD) and comorbidities, including depression, obesity, asthma, and allergic rhinitis. Although observational studies often cannot establish robust causality between potential risk factors and AD, Mendelian randomization minimizes confounding when exploring causality by relying on random allelic assortment at birth. In this study, we systematically reviewed 30 Mendelian randomization studies in AD. Body mass index, gut microbial flora, the IL-18 signaling pathway, and gastroesophageal reflux disease were among the causal factors for AD, whereas AD was causal for several medical conditions, including heart failure, rheumatoid arthritis, and conjunctivitis. These insights may improve preventive counseling in AD.

Effects of comorbid asthma and eczema on child and family quality of life

Paediatric chronic health conditions are associated with poorer psychological wellbeing and quality of life for children and families. This study investigated differences in child and parent/family quality of life between families of children with asthma only, eczema only, or both asthma and eczema, and tested predictors of child and parent/family quality of life. A convenience sample of 106 families completed parent-report measures of child and parent/family quality of life, child emotional and behavioural difficulties, parent adjustment and parenting practices. Between-groups ANOVAs indicated no differences for child quality of life, whereas parent/family quality of life was worse for those with eczema only compared to asthma only. Multiple linear regression revealed that child emotional difficulties predicted worse child quality of life, whereas worse parent adjustment, child emotional difficulties and eczema only (compared to both asthma and eczema) predicted worse parent quality of life. Results suggest that families of children with eczema may be at particular risk for impaired parent/family quality of life. Interventions that take a family-centred approach to improving child and parent adjustment should be investigated as an adjunct to medical treatment to reduce the impact of chronic health conditions on quality of life for children and families.

Insights from the COCOA birth cohort: The origins of childhood allergic diseases and future perspectives

The ongoing COhort for Childhood Origin of Asthma and allergic diseases (COCOA) study is a prospective birth cohort investigating the origin and natural courses of childhood allergic diseases, including atopic dermatitis, food allergy, allergic rhinitis and asthma, with long-term prognosis. Initiated under the premise that allergic diseases result from a complex interplay of immune development alterations, environmental exposures, and host susceptibility, the COCOA study explores these dynamic interactions during prenatal and postnatal periods, framed within the hygiene and microbial hypotheses alongside the developmental origins of health and disease (DOHaD) hypothesis. The scope of the COCOA study extends to genetic predispositions, indoor and outdoor environmental variables affecting mothers and their offsprings such as outdoor and indoor air pollution, psychological factors, diets, and the microbiomes of skin, gut, and airway. We have embarked on in-depth investigations of diverse risk factors and the pathophysiological underpinnings of allergic diseases. By employing multi-omics approaches-proteomics, transcriptomics, and metabolomics-we gain deeper insights into the distinct pathophysiological processes across various endotypes of childhood allergic diseases, incorporating the exposome using extensive resources within the COCOA study. Integration with large-scale datasets, such as national health insurance records, enhances robustness and mitigates potential limitations inherent to birth cohort studies. As part of global networks focused on childhood allergic diseases, the COCOA study fosters collaborative research across multiple cohorts. The findings from the COCOA study are instrumental in informing precision medicine strategies for childhood allergic diseases, underpinning the establishment of disease trajectories.

A Positive Causal Effect of Shrimp Allergy on Major Depressive Disorder Mediated by Allergy- and Immune-Related Pathways in the East Asian Population

BACKGROUND

Observational studies have implied a potential correlation between allergic diseases and major depressive disorder (MDD). However, the relationship is still inconclusive as it is likely to be interfered with by substantial confounding factors and potential reverse causality. The present study aimed to investigate causal correlation of the two diseases by a Mendelian randomization (MR) study and further elucidate the underlying molecular mechanisms.

METHODS

With the biggest summary datasets of a genome-wide association study (GWAS) in the East Asian population, we conducted a two-sample, bidirectional MR study to assess the causal correlation between shrimp allergy (SA) and MDD. Subsequently, we identified the pleiotropic genes' susceptibility to the two diseases at whole-genome and tissue-specific levels, respectively. Enriched GO sets and KEGG pathways were also discovered to elucidate the potential underlying mechanisms.

RESULTS

With the most suitable MR method, SA was identified as a causal risk factor for MDD based on three different groups of independent genetic instruments, respectively (p < 2.81 × 10-2). In contrast, we did not observe a significant causal effect of MDD on SA. The GWAS-pairwise program successfully identified seven pleiotropic genetic variants (PPA3 > 0.8), indicating that the two diseases indeed have a shared genetic basis. At a whole-genome level, the MAGMA program identified 44 pleiotropic genes, which were enriched in allergy-related pathways, such as antigen processing and presentation pathway (p = 1.46 × 10-2). In brain-specific tissue, the S-MultiXcan program found 17 pleiotropic genes that were significantly enriched in immune-related pathways and GO sets, including asthma-related pathway, T-cell activation-related, and major histocompatibility complex protein-related GO sets. Regarding whole-blood tissue, the program identified six pleiotropic genes that are significantly enriched in tolerance induction-related GO sets.

CONCLUSIONS

The present study for the first time indicated a significant causal effect of SA on the occurrence of MDD, but the reverse was not true. Enrichment analyses of pleiotropic genes at whole-genome and tissue-specific levels implied the involvement of allergy and immune-related pathways in the shared genetic mechanism of the two diseases. Elucidating the causal effect and the acting direction may be beneficial in reducing the incidence rate of MDD for the massive group of SA patients in the East Asian region.

Study of Allergy and Sensitization Relationship in Children and Parents in Southern China

INTRODUCTION

The incidence of allergic diseases has increased globally, with genetics playing an essential role in these conditions' development. However, there is still a gap in understanding of how parental allergy status affects children's allergies.

METHODS

An electronic questionnaire was used to assess allergy-related symptoms in kindergarten children and their parents, with a clinical diagnosis and concurrent serum allergen-specific immunoglobulin E (IgE), total IgE, and blood cell counts obtained.

RESULTS

88 family groups were enrolled, with allergy prevalence of 85.2% in children, 50% in fathers, and 42% in mothers. Allergic rhinoconjunctivitis was the most common allergic disease. When the mother had an allergy, the children's allergy diagnosis rate was 91.3%; 86.67% when the father had an allergy; and 85.71% when both parents had allergies. The child sensitization rate was 78.26% when the father had sensitization, 59.09% just as the mother had sensitization, and 84.21% when both parents had sensitization. Paternal allergies affected children's quality of life due to allergic rhinitis but not their rhinitis symptoms. Maternal allergies or sensitization did not significantly affect children's symptoms or quality-of-life scores.

CONCLUSION

The study found a positive correlation between childhood and parental allergies, and further studies are needed to confirm the findings.

European and multi-ancestry genome-wide association meta-analysis of atopic dermatitis highlights importance of systemic immune regulation

Atopic dermatitis (AD) is a common inflammatory skin condition and prior genome-wide association studies (GWAS) have identified 71 associated loci. In the current study we conducted the largest AD GWAS to date (discovery N = 1,086,394, replication N = 3,604,027), combining previously reported cohorts with additional available data. We identified 81 loci (29 novel) in the European-only analysis (which all replicated in a separate European analysis) and 10 additional loci in the multi-ancestry analysis (3 novel). Eight variants from the multi-ancestry analysis replicated in at least one of the populations tested (European, Latino or African), while two may be specific to individuals of Japanese ancestry. AD loci showed enrichment for DNAse I hypersensitivity and eQTL associations in blood. At each locus we prioritised candidate genes by integrating multi-omic data. The implicated genes are predominantly in immune pathways of relevance to atopic inflammation and some offer drug repurposing opportunities.

Common mental health disorders in adults with inflammatory skin conditions: nationwide population-based matched cohort studies in the UK

BACKGROUND

Psoriasis and atopic eczema are common inflammatory skin diseases. Existing research has identified increased risks of common mental disorders (anxiety, depression) in people with eczema and psoriasis; however, explanations for the associations remain unclear. We aimed to establish the risk factors for mental illness in those with eczema or psoriasis and identify the population groups most at risk.

METHODS

We used routinely collected data from the UK Clinical Practice Research Datalink (CPRD) GOLD. Adults registered with a general practice in CPRD (1997-2019) were eligible for inclusion. Individuals with eczema/psoriasis were matched (age, sex, practice) to up to five adults without eczema/psoriasis. We used Cox regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for hazards of anxiety or depression in people with eczema/psoriasis compared to people without. We adjusted for known confounders (deprivation, asthma [eczema], psoriatic arthritis [psoriasis], Charlson comorbidity index, calendar period) and potential mediators (harmful alcohol use, body mass index [BMI], smoking status, and, in eczema only, sleep quality [insomnia diagnoses, specific sleep problem medications] and high-dose oral glucocorticoids).

RESULTS

We identified two cohorts with and without eczema (1,032,782, matched to 4,990,125 without), and with and without psoriasis (366,884, matched to 1,834,330 without). Sleep quality was imbalanced in the eczema cohorts, twice as many people with eczema had evidence of poor sleep at baseline than those without eczema, including over 20% of those with severe eczema. After adjusting for potential confounders and mediators, eczema and psoriasis were associated with anxiety (adjusted HR [95% CI]: eczema 1.14 [1.13-1.16], psoriasis 1.17 [1.15-1.19]) and depression (adjusted HR [95% CI]: eczema 1.11 [1.1-1.12], psoriasis 1.21 [1.19-1.22]). However, we found evidence that these increased hazards are unlikely to be constant over time and were especially high 1-year after study entry.

CONCLUSIONS

Atopic eczema and psoriasis are associated with increased incidence of anxiety and depression in adults. These associations may be mediated through known modifiable risk factors, especially sleep quality in people with eczema. Our findings highlight potential opportunities for the prevention of anxiety and depression in people with eczema/psoriasis through treatment of modifiable risk factors and enhanced eczema/psoriasis management.

The Immunoseasonal Theory of Psychiatric Disorders

Although the influence of the weather on the well-being and mental health of psychiatric patients has been widely seen, the relationships between various seasonal weather factors and depressive, manic, anxiety, and psychotic states have not been systematized in the literature. The current article describes the seasonal changes in weather-related immune responses and their impact on the development of episodes of depression, mania, psychosis, and anxiety, highlighting the T-helper 1 (Th1) and Th2 immune balance as their potential trigger. In autumn-winter depression, the hyperactivation of the Th1 system, possibly by microbial/airborne pathogens, may lead to the inflammatory inhibition of prefrontal activity and the subcortical centers responsible for mood, drive, and motivation. Depressive mood periods are present in most people suffering from schizophrenia. In the spring and summertime, when the compensating anti-Th1 property of the Th2 immune system is activated, it decreases the Th1 response. In individuals immunogenetically susceptible to psychosis and mania, the inhibition of Th1 by the Th2 system may be excessive and lead to Th2-related frontal and subcortical hyperactivation and subsequent psychosis. In people suffering from bipolar disorder, hyperintense changes in white matter may be responsible for the partial activation of subcortical areas, preventing full paranoid psychosis. Thus, psychosis may be mood-congruent in affective disorders.

On the Inheritance of Microbiome-Deficiency: Paediatric Functional Gastrointestinal Disorders, the Immune System and the Gut–Brain Axis

Like the majority of non-communicable diseases that have recently gained attention, functional gastrointestinal (GI) disorders (FGID) in both children and adults are caused by a variety of medical conditions. In general, while it is often thought that common conditions such as obesity may cause other problems, for example, asthma or mental health issues, more consideration needs to be given to the possibility that they could both be brought on by a single underlying problem. Based on the variations in non-communicable disease, in recent years, our group has been revisiting the exact role of the intestinal microbiome within the Vertebrata. While the metabolic products of the microbiome have a role to play in the adult, our tentative conclusion is that the fully functioning, mutualistic microbiome has a primary role: to transfer antigen information from the mother to the neonate in order to calibrate its immune system, allowing it to survive within the microbial environment into which it will emerge. Granted that the microbiome possesses such a function, logic suggests the need for a robust, flexible, mechanism allowing for the partition of nutrition in the mature animal, thus ensuring the continued existence of both the vertebrate host and microbial guest, even under potentially unfavourable conditions. It is feasible that this partition process acts by altering the rate of peristalsis following communication through the gut–brain axis. The final step of this animal–microbiota symbiosis would then be when key microbes are transferred from the female to her progeny, either live offspring or eggs. According to this scheme, each animal inherits twice, once from its parents’ genetic material and once from the mother’s microbiome with the aid of the father’s seminal microbiome, which helps determine the expression of the parental genes. The key point is that the failure of this latter inheritance in humans leads to the distinctive manifestations of functional FGID disorders including inflammation and gut motility disturbances. Furthermore, it seems likely that the critical microbiome–gut association occurs in the first few hours of independent life, in a process that we term handshaking. Note that even if obvious disease in childhood is avoided, the underlying disorders may intrude later in youth or adulthood with immune system disruption coexisting with gut–brain axis issues such as excessive weight gain and poor mental health. In principle, investigating and perhaps supplementing the maternal microbiota provide clinicians with an unprecedented opportunity to intervene in long-term disease processes, even before the child is born.

Microbiome–Gut Dissociation in the Neonate: Autism-Related Developmental Brain Disease and the Origin of the Placebo Effect

While the importance of the intestinal microbiome has been realised for a number of years, the significance of the phrase microbiota–gut–brain axis is only just beginning to be fully appreciated. Our recent work has focused on the microbiome as if it were a single entity, modifying the expression of the genetic inheritance of the individual by the generation of interkingdom signalling molecules, semiochemicals, such as dopamine. In our view, the purpose of the microbiome is to convey information about the microbial environment of the mother so as to calibrate the immune system of the new-born, giving it the ability to distinguish harmful pathogens from the harmless antigens of pollen, for example, or to help distinguish self from non-self. In turn, this requires the partition of nutrition between the adult and its microbiome to ensure that both entities remain viable until the process of reproduction. Accordingly, the failure of a degraded microbiome to interact with the developing gut of the neonate leads to failure of this partition in the adult: to low faecal energy excretion, excessive fat storage, and concomitant problems with the immune system. Similarly, a weakened gut–brain axis distorts interoceptive input to the brain, increasing the risk of psychiatric diseases such as autism. These effects account for David Barker’s 1990 suggestion of “the fetal and infant origins of adult disease”, including schizophrenia, and David Strachan’s 1989 observation of childhood immune system diseases, such as hay fever and asthma. The industrialisation of modern life is increasing the intensity and scale of these physical and psychiatric diseases and it seems likely that subclinical heavy metal poisoning of the microbiome contributes to these problems. Finally, the recent observation of Harald Brüssow, that reported intestinal bacterial composition does not adequately reflect the patterns of disease, would be accounted for if microbial eukaryotes were the key determinant of microbiome effectiveness. In this view, the relative success of “probiotic” bacteria is due to their temporary immune system activation of the gut–brain axis, in turn suggesting a potential mechanism for the placebo effect.

Markers of Schizophrenia—A Critical Narrative Update

Schizophrenia is a long-term mental disease, associated with functional impairment. Therefore, it is important to make an accurate diagnosis and implement the proper treatment. Biomarkers may be a potential tool for these purposes. Regarding advances in biomarker studies in psychosis, the current symptom-based criteria seem to be no longer sufficient in clinical settings. This narrative review describes biomarkers of psychosis focusing on the biochemical (peripheral and central), neurophysiological, neuropsychological and neuroimaging findings as well as the multimodal approach related with them. Endophenotype markers (especially neuropsychological and occulomotor disturbances) can be currently used in a clinical settings, whereas neuroimaging glutamate/glutamine and D2/D3 receptor density changes, as well as immunological Th2 and PRL levels, seem to be potential biomarkers that need further accuracy tests. When searching for biochemical/immunological markers in the diagnosis of psychosis, the appropriate time of body fluid collection needs to be considered to minimize the influence of the stress axis on their concentrations. In schizophrenia diagnostics, a multimodal approach seems to be highly recommended.

Dissecting the Association of Genetically Predicted Neuroticism with Coronary Artery Disease: A Two-Sample Mendelian Randomization Study

Background: Observational studies on the association between neuroticism and coronary artery disease (CAD) are still rare, and the results of existing studies are not consistent. The present study aimed to explore causal associations of neuroticism with CAD. Methods: The summary-level data of GWAS for neuroticism and 12 items used to assess neuroticism were extracted from the UK Biobank, and included up to 380,506 participants. The general data for CAD were obtained from the CARDIoGRAMplusC4D consortium, which assembled 60,801 CAD patients and 123,504 non-cases. Single-nucleotide polymorphisms associated with neuroticism and 12 items at genome-wide significance were explored as instrumental variables. Two-sample Mendelian randomization (TSMR) analyses were performed to evaluate causal associations amongst the genetically predicted neuroticism and 12 items with CAD. Results: The present TSMR study did not reveal the genetic association of neuroticism with CAD. The calculated ORs for CAD using inverse-variance weighted, weighted median, and MR-Egger analysis were 1.12 (p-value = 0.187), 0.99 (p-value = 0.943), and 0.82 (p-value = 0.683), respectively. Further TSMR analysis of 12 dichotomous items for assessing neuroticism suggested that mood swings genetically increased the risk of CAD (OR = 1.67, p-value < 0.001). Conclusions: This study reported no genetically causal association of neuroticism with CAD. The present study also found that mood swings may genetically increase the risk of CAD. These findings may highlight the potential of mood control as a preventive measure for CAD.