Translational Psychiatry

Mental disorders (MDs) are emerging as a significant threat to global health, with their intricate pathogenesis making the discovery of effective treatments a challenging endeavor. Currently, nutritional intervention, especially polyunsaturated fatty acids (PUFAs), has garnered widespread attention. This review aims to explore the potential causal relationship between PUFAs and MDs using Mendelian randomization (MR) meta-analysis. The study employed two-sample MR technology to analyze the association between PUFAs (including omega-3, omega-3%, omega-6, omega-6%, and the omega-6:omega-3 ratio) and MDs. It utilized data from genome-wide association studies to assess the role of PUFAs in 12 major MDs. The MR analysis revealed a causal link between genetically predicted omega-3 and MDs such as obsessive-compulsive disorder, bipolar disorder, schizophrenia, and major depressive disorder. Omega-3% showed protective effects against certain diseases, including emotional personality disorder. Meanwhile, the inverse correlation between genetically predicted omega-6 and the risk of attention deficit/hyperactivity disorder, as well as the association between a high omega-6:omega-3 ratio and increased risk of depression and other mood disorders, were also supported by meta-analyses. These findings suggest that high levels of omega-3 and omega-3% may reduce the risk of MDs, while a high omega-6:omega-3 ratio may increase the risk. The study highlights the potential of PUFAs, particularly omega-3, in the prevention and treatment of MDs, while also noting the complex interactions between omega-3 and omega-6 and their impact on MDs, which necessitates further research. These findings provide a scientific basis for future clinical trials and the development of dietary intervention measures.

Exposure to chronic stress and traumatic experiences impacts brain health and development, which may lead to Post Traumatic Stress Disorder (PTSD), other mental health conditions, or altered resilience. Although certain behavioral and social factors have been associated resilience, little is known about the cellular and genomic mechanisms contributing to resilience or developing PTSD. Here, we present a novel model system called "Stress-in-a-dish" (SIAD) to study the molecular signature of chronic and acute stress in differentiated cortical organoids. Derived from human induced Pluripotent Stem Cells (iPSCs), mature organoids responded to cortisol with differential expression of genes. Many genes were associated with expected corticosteroid pathways, and some have not been previously linked to PTSD. A previously unknown potential contribution of astrocytes to the etiology of stress responses was also found. Our results suggest a novel paradigm for studying stress in a dish that opens up new opportunities to understand the biological basis of PTSD and resilience.

The men and women involved in rescue and recovery operations at the 9/11 World Trade Center (WTC) site have a greater prevalence (23%) of persistent, clinically significant post- traumatic stress disorder (PTSD). Recent structural and functional magnetic resonance imaging (MRI) studies demonstrate significant neural differences between WTC responders with and without PTSD. Here, we used brain age, a novel MRI-based data-driven biomarker optimized to detect accelerated structural aging, and examined the impact of PTSD on this process. Using BrainAgeNeXt, a novel convolutional neural network trained and validated on 11,574 magnetic resonance imaging (MRI) T1- weighted scans, we predicted brain age in WTC responders with PTSD (WTC-PTSD, n = 47) and age/sex matched responders without PTSD (non-PTSD, n = 52). Predicted Age Difference (PAD) was then calculated for each WTC responder by subtracting chronological age from brain age. A positive PAD indicates that the responders brain is aging faster than expected for their chronological age. We found that PAD is significantly greater with WTC-PTSD compared to non-PTSD responders (p < 0.001). Further, we found that WTC exposure duration (months working on site) moderates the association between PTSD and PAD (p=0.0050). Our results suggested that brain age is a valid biomarker to compare aging trajectories in responders with and without PTSD. In particular, PTSD may be a substantial risk factor for accelerated neurodegeneration in this vulnerable and aging population.

Background: Post-traumatic stress disorder (PTSD) remains highly prevalent affecting ~23% of World Trade Center (WTC) responders more than two decades after 9/11. While MRI studies have identified neural differences associated with PTSD, these findings have not translated into improved treatment. We introduce a novel multimodal MRI approach, DAta-driven Network Connectivity Estimate (DANCE), integrating structural and functional magnetic resonance imaging (MRI) to better capture PTSD mechanisms and inform biomarkers. Methods: In 96 WTC responders , including 45 with current WTC-related PTSD and 51 without PTSD. We applied graph theory to resting-state functional MRI to identify functional hubs via eigenvector centrality and identified divergence between groups using partial least squares discriminant analysis (PLS-DA). From diffusion MRI, we reconstructed five anatomical tracts (i.e., streamlines) in the temporal lobes. Using DANCE, we quantified the differential distribution of streamlines of the reconstructed tracts connecting the functional hubs. We then tested whether WTC exposure duration moderated associations between PTSD and DANCE indices. Results: Responders with PTSD showed altered centrality in nine functional hubs (AUC=0.75 (0.651-0.847)) including bilateral anterior inferior temporal gyrus, right superior parietal lobule, right anterior parahippocampal gyrus, right anterior/posterior superior temporal gyrus (STG), right caudate nucleus, left amygdala and brainstem. Connectivity differences emerged in four tracts: hippocampus, parahippocampus, inferior and superior temporal gyri (STG). DANCE differed in the inferior fronto-occipital fasciculus (IFOF), medial (IFLmed) and lateral (IFLlat) components of the inferior longitudinal fasciculus and in the middle longitudinal fascicle (MdLF). WTC exposure duration significantly moderated the association between PTSD and DANCE values in the IFLmed, right posterior STG (p= 0.035). Conclusion: Our novel DANCE approach revealed converging functional and anatomical connectivity alterations uniquely associated with PTSD in WTC responders and offers compelling evidence for distinct neurobiological signatures of the disorder. These findings significantly advance our understanding of PTSD pathophysiology and highlight potential biomarkers for diagnosis and targeted intervention.

Context and ObjectiveSteroid hormone profiles in affective disorders suggest hypothalamic- pituitary-adrenal (HPA) axis dysregulation and may reveal novel therapeutic targets. However, most existing studies focus narrowly on glucocorticoids. This study aims to comprehensively characterize alterations in the steroid metabolome of adolescents with depressive symptoms. Design, Setting, and PatientsThis cross-sectional study analyzed the urinary excretion of 39 steroid metabolites (via gas chromatography-mass spectrometry) from 75 adolescent psychiatric patients with depressive symptoms (63 females, age 15.6 {+/-} 1.3 years) and 75 healthy controls (64 females, age 15.3 {+/-} 1.3 years), matched for age, sex, and pubertal status. ResultsPatients exhibited significantly elevated excretion rates ({micro}g/24h) of corticosterone metabolites (median = 608.4, interquartile range (IQR): 342.4 - 1208.2 vs. controls: median = 321.0, IQR: 243.9 - 443.8), dehydroepiandrosterone (DHEA) metabolites (median = 1253.8, IQR: 569.8 - 2796.2 vs. median = 519.5, IQR: 254.0 - 1028.7), androgen metabolites (median = 6721.0, IQR: 4185.6 - 9395.8 vs. median = 3680.4, IQR: 2510.8 - 5419.0), and individual progesterone and glucocorticoid metabolites, while estradiol excretion was lower (median = 4.0, IQR: 2.9 - 5.8 vs. median = 5.8, IQR: 4.3 - 7.7). Analyses of enzyme activities via multivariate machine learning identified the tetrahydrated urinary metabolite ratio of 11-deoxycorticosterone (TH-DOC) to corticosterone metabolites as a biomarker to distinguish patients from controls (AUC = 0.800, 95%-CI [0.702 - 0.882]). ConclusionsElevated excretion rates of ACTH-dependent hormones indicate chronic stress in adolescents with depressive symptoms. The TH-DOC-to-corticosterone metabolite ratio may help identify at-risk patients or guide personalized therapies.

Oral cannabidiol (CBD) treatment has been suggested to alleviate severe symptoms of autism spectrum disorder (ASD). While many CBD preparations have been studied in clinical trials involving ASD, none has used purified CBD preparations or preparations approved by the U.S. Food and Drug Administration, nor have they focused on children with ASD with higher support needs. Previous studies have identified several candidate electrophysiological biomarkers of cognitive and behavioral disabilities in ASD, with emerging biomarkers including periodic (oscillatory) and aperiodic measures of neural activity. We analyzed electroencephalography (EEG) recordings from 24 boys with ASD and higher support needs (aged 7-14 years) from a prior double-blind, placebo-controlled, crossover Phase II Clinical Trial (NCT04517799) that investigated whether 8 weeks of daily CBD treatment (titrated to 20 mg/kg/day) improved severe behavioral problems, measured at baseline, post-CBD, post-placebo, and post-washout. Using linear mixed effect models, we found that aperiodic EEG measures varied with CBD metabolite levels in blood, as evidenced by a larger aperiodic offset across the scalp and a decreased aperiodic exponent across occipital electrodes. Furthermore, CBD metabolite levels in blood had a positive association with receptive vocabulary, nonverbal intelligence and visuomotor coordination. Our data suggest that this daily CBD preparation and administration schedule produced mixed effects, with some children showing improvements in cognitive and behavioral abilities while others demonstrated limited changes. Our findings support the inclusion of aperiodic EEG measures alongside traditional oscillatory EEG measures as candidate biomarkers for tracking the variable clinical impact of purified CBD treatment in children with ASD.

A growing number of studies point to a key role of the amygdala in Autism Spectrum Disorders (ASD). The amygdala is involved in several processes in ASD including emotional valence, facial recognition, regulation of social learning, empathy, and anxiety. Brain imaging and postmortem studies demonstrate altered amygdala development in children with ASD, associated with impairment in social behavior and anxiety. There is limited information regarding the molecular pathology of the amygdala in children with ASD. We conducted RNAseq profiling on postmortem amygdala samples from male children (4-14 yrs old) with ASD (n=8) and normotypic male children (n=6). Furthermore, we conducted drug repurposing analysis to identify compounds predicted to reverse the transcriptomic signatures identified in order to identify potential therapeutic targets for development of early intervention treatments. Full transcriptome gene expression profiling implicated molecular pathways involved in neuroimmune signaling, glycogen and carbohydrate metabolism, matrix metalloproteases, neurodevelopment, estrogen receptor signaling, and synaptic signaling. Targeted pathway analysis of the top 10% of differentially expressed genes implicated pathways involved in extracellular matrix organization, immune signaling, and synaptic signaling. Our drug repurposing analysis identified sleep modifying compounds and anti-inflammatory compounds including COX2 and GSK3 inhibitors amongst the top predicted therapeutic compound classifications. PDGF receptor tyrosine kinase inhibitors were identified as a top potential therapeutic mechanism of action. Our results point to alterations in immune signaling, extracellular matrix organization, and synaptic signaling in the amygdala of children with ASD. Furthermore, our results identified a number of potential therapeutic drug targets for development of early intervention strategies.

Problematic Sexual Behaviour (PSB) is defined as difficult to control recurrent sexual behaviours that continue despite adverse consequences, leading to social and functional impairment. There is debate whether PSB is a disorder of compulsion or addiction; PSB often co-occurs with neuropsychiatric disorders, but further elucidation regarding underlying biology is required. A deficiency in reward neurotransmitter systems (reward deficiency syndrome: RDS) may underlie a shared vulnerability to addiction. We conducted the first case-control genome wide association study (GWAS) of PSB in patients (n=448), and comparison participants with (n=196) and without PSB (n=1488). We used polygenic risk scores (PRS) to test genetic overlap with related psychiatric, behavioural and personality phenotypes. Three models were used: 1) All-PSB (patient + comparison) vs. controls, 2) Patient-PSB vs controls, and 3) RDS (yes/no). Results suggested genetic overlap of PSB with psychiatric conditions, with PRS for major depression, substance use, and others predicting PSB status. PRS for related behavioural phenotypes (e.g., externalizing, age at first sex, number of lifetime sexual partners) and personality traits also predicted PSB. The patient model showed stronger associations than the All-PSB model, and RDS had both shared and distinct genetics with PSB. As expected with the sample size, only suggestive hits were observed with single variant and gene-based tests. PSB may share genetic mechanisms with various conditions. Further research in larger cohorts is needed to better understand the underlying genetics and environmental factors involved, and to improve diagnostic classification, intervention and treatment prospects.

ObjectiveAssociations have been seen between suicidal behavior and differential DNA methylation of certain genes, with one study showing significant hypomethylation of ARHGEF38 in postmortem brain samples from individuals with bipolar disorder who died by suicide. Our objective was to explore ARHGEF38 methylation in individuals with bipolar disorder and a history of suicide attempt. MethodWith pyrosequencing, we looked at the previously identified region of interest in ARHGEF38. We investigated the methylation levels of 3 CpG sites in 47 individuals with bipolar disorder and a history of suicide attempt, 47 individuals with bipolar disorder without a history of suicide attempt, and 47 non-bipolar disorder controls. ResultsNone of the CpG sites measured had an association between groups, although there were distinct clusters of differential methylation in each group. Applying genotypes of SNPs found in the region of interest, rs2121558 and rs1447093, these clusters showed stepwise methylation at each CpG site, regardless of phenotype. ConclusionsIn this relatively small sample size study, differential methylation in ARHGEF38 was not associated with history of suicide attempt, failing to replicate findings from a related outcome, suicide death. However, we did provide evidence of SNP and DNA methylation interplay in this region. This highlights the potential relevance of considering genetics when interrogating epigenetic mechanisms. HighlightsO_LIARHGEF38 methylation is not associated with bipolar disorder and suicide attempt C_LIO_LIMethylation of ARHGEF38 is heavily influenced by the presence of SNPs C_LIO_LISuicide phenotype, genetics, and sample type impact DNA methylation C_LI

BackgroundMore than 180 million cases of COVID-19 have been reported worldwide. It has been proposed that neuropsychiatric disorders may be risk factors and/or consequences of COVID-19 infection. However, observational studies could be affected by confounding bias. MethodsWe performed bi-directional two-sample Mendelian randomization (MR) analysis to evaluate causal relationships between liability to COVID-19 (and severe/critical infection) and a wide range of neuropsychiatric disorders or traits. We employed GWAS summary statistics from the COVID-19 Host Genetics Initiative. A variety of MR methods including those accounting for horizontal pleiotropy were employed. ResultsOverall, we observed evidence that liability to COVID-19 or severe infection may be causally associated with higher risks of post-traumatic stress disorder (PTSD), bipolar disorder (BD) (especially BD II), schizophrenia (SCZ), attention deficit hyperactivity disorder (ADHD) and suicidal thought (ST) when compared to the general population. On the other hand, liability to a few psychiatric traits/disorders, for example ADHD, alcohol and opioid use disorders may be causally associated with higher risks of COVID-19 infection or severe disease. In genetic correlation analysis, cannabis use disorder, ADHD, and anxiety showed significant and positive genetic correlation with critical or hospitalized infection. All the above findings passed multiple testing correction at a false discovery rate (FDR)<0.05. For pneumonia, in general we observed a different pattern of causal associations. We observed bi-directional positive associations with depression- and anxiety-related phenotypes. ConclusionsIn summary, this study provides evidence for tentative bi-directional causal associations between liability to COVID-19 (and severe infection) and a number of neuropsychiatric disorders. Further replications and prospective studies are required to verify the findings.

Selective serotonin reuptake inhibitors (SSRIs) are often prescribed during pregnancy. Yet, epidemiological studies link in-utero SSRI exposure with neurodevelopmental disorders, such as autism and ADHD. The potential molecular mechanisms by which SSRIs impact early neurodevelopment are not fully understood. We exposed neuroepithelial stem cells derived from four human induced pluripotent stem cells lines to fluoxetine, citalopram, sertraline, and paroxetine. We then assessed cellular viability, reactive oxygen species (ROS) levels, mitochondrial function using adenosine triphosphate (ATP) assays, and performed high-throughput metabolomics at two timepoints: proliferation and neural differentiation stages. The key metabolic findings were validated in the in-vitro model and in a complementary population-based cohort, the Barwon Infant Study, consisting of 1074 mother-child pairs with analysed cord-blood metabolomes. Sertraline and paroxetine significantly decreased ROS and ATP levels, indicating mitochondrial alteration. Metabolomic profiling revealed consistent elevation of three lysophosphatidylcholines (LPCs 16:0, 18:0, 18:1) across all SSRIs except citalopram. We further observed elevated LPC levels in the cord blood of infants prenatally exposed to SSRIs, with a dose-dependent correlation to autism and ADHD-related symptoms at age two. Furthermore, the three LPCs modulated ROS and ATP levels in the neural cells. These findings provide insights into SSRI-induced molecular changes, highlight candidate metabolites that may warrant further investigation as indicators of SSRI exposure, and emphasise the need for exploring prenatal SSRI exposure effects and neurodevelopmental outcomes.

Only recently have human postmortem brain studies of differential gene expression (DGE) associated with opioid overdose death (OOD) been published; sample sizes from these studies have been modest (N = 40-153). To increase statistical power to identify OOD-associated genes, we leveraged human prefrontal cortex RNAseq data from four independent OOD studies and conducted a transcriptome-wide DGE meta-analysis (N = 285). Using a unified gene expression data processing and analysis framework across studies, we meta-analyzed 20LJ098 genes and found 335 significant differentially expressed genes (DEGs) by OOD status (false discovery rate < 0.05). Of these, 66 DEGs were among the list of 303 genes reported as OOD-associated in prior prefrontal cortex molecular studies, including genes/gene families (e.g., OPRK1, NPAS4, DUSP, EGR). The remaining 269 DEGs were not previously reported (e.g., NR4A2, SYT1, HCRTR2, BDNF). There was little evidence of genetic drivers for the observed differences in gene expression between opioid addiction cases and controls. Enrichment analyses for the DEGs across molecular pathway and biological process databases highlight an interconnected set of genes and pathways from orexin and tyrosine kinase receptors through MEK/ERK/MAPK signaling to affect neuronal plasticity.

Opioid use disorders cause major morbidity and mortality, and there is a pressing need for novel mechanistic targets and biomarkers for diagnosis and prognosis. Exposure to mu-opioid receptor (MOR) agonists causes changes in cytokine and inflammatory protein networks in peripheral blood, and also in brain glia and neurons. Individuals with heroin use disorder (iHUD) show dysregulated levels of several cytokines in blood. However, there is limited data on a comprehensive panel of such markers in iHUD versus healthy controls (HC), especially as a multi-target biomarker. We used a validated proximity extension assay for relative quantification of 92 cytokines and inflammatory proteins in serum of iHUD on medication assisted therapy (MAT; n=21), versus HC (n=24). Twenty-nine targets showed significant group differences (primarily iHUD>HC), surviving multiple comparison correction (p=0.05). This included 19 members of canonical cytokine families, including specific chemokines, interleukins, growth factors, and tumor necrosis factor (TNF)-related proteins. For dimensionality reduction, data from these 19 cytokines were entered into a principal component (PC) analysis, and PC1 scores were iHUD>HC (p<0.0001). A receiver-operating characteristic (ROC) curve analysis yielded an AUROC=91.7% (p<0.0001). This PC1 score remained a positive predictor of being in the HUD group in a multivariable logistic regression, which included demographic/clinical variables. Overall, this study shows a panel of cytokines that differ significantly between iHUD and HC, and provides a multi-target "cytokine biomarker score" for potential diagnostic purposes, and examination of disease severity.

BackgroundChronic stress increases risk for neuropsychiatric disorders in humans. By modeling stress-induced changes in animals, we may improve diagnosis or treatment of these disorders. Successful translation benefits from studies with sufficient statistical power and outcome measurements that can be directly compared across species. We performed a meta-analysis to examine the impact of chronic stress on the whole blood transcriptome. MethodsDatasets were systematically identified in Gemma, a database of reprocessed public transcriptional profiling studies; datasets GSE68076, GSE72262, and GSE84185 met inclusion/exclusion parameters. Each study exposed eight-week old mice to chronic stress (5-10 days social defeat stress or 6-8 weeks chronic mild stress). The final sample size was n=92 (n=45 Non-Stress/n=47 Stress). Stress-related differential expression in each dataset was quantified using the Limma pipeline followed by empirical Bayes moderation. For the 9,219 genes represented in all three datasets, we ran a meta-analysis of Log(2) Fold Changes using a random effects model and corrected for false discovery rate (FDR). Functional patterns were assessed with fast Gene Set Enrichment Analysis. Cell type specific enrichment for each of the differentially expressed genes was further explored using a public 10x genomics scRNA-Seq dataset from mouse peripheral blood mononuclear cells. ResultsFindings included 23 downregulated and 16 upregulated transcripts in stress-exposed mice (FDR<0.05). Results indicated a down-regulation in gene sets related to B cells, immune response, DNA and chromatin regulation, ribosomal activity, translation, and catabolic cellular processes. Upregulated gene sets related to erythrocytes and oxygen binding. ConclusionOur results provide molecular insight into stress-related immune dysregulation and add weight to the hypothesis that environmental stress escalates cellular aging, supporting the use of blood transcriptome as a bridge between human and rodent models. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=99 SRC="FIGDIR/small/657043v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@161fc2eorg.highwire.dtl.DTLVardef@1f358b9org.highwire.dtl.DTLVardef@145ef33org.highwire.dtl.DTLVardef@5b1169_HPS_FORMAT_FIGEXP M_FIG C_FIG Key pointsSuccessful translational research benefits from studies with outcome measurements that can be directly compared across species and sufficient statistical power. The present report is a meta-analysis of three mouse experiments examining the impact of chronic stress on the whole blood transcriptome. Our results provide insight into stress-related immune dysregulation and add weight to the hypothesis that environmental stress escalates cellular aging. These findings illustrate the utility of the blood transcriptome as a bridge between human and rodent models.

Social anxiety disorder (SAD) is among the most prevalent anxiety disorders, and it has been associated with signs of advanced biological ageing. Despite this, brain age research on anxiety disorders remains limited. This mega-analysis investigated brain ageing in adults with SAD within the ENIGMA-Anxiety Working Group. Structural MRI scans from 576 participants with SAD and 1 355 non-affected healthy controls (HCs) across 26 international samples were included. Brain age was estimated from 77 cortical and subcortical regions using a publicly available ENIGMA brain age model. The brain-predicted age difference (brain-PAD) was calculated as the difference between brain age and chronological age. Group and subgroup differences (comorbidity, medication) were assessed using linear mixed-effect models. In the full sample, there was no group difference in brain-PAD ({beta}diagnosis (SE)=0.70 (0.37) years, p=0.061). In a subgroup of participants with SAD with comorbid anxiety disorders (n=184 SAD, n=1 355 HCs), a brain-PAD of +2.39 (0.93) years (Cohen's d=0.23, pFDR=0.003) was observed. This brain-PAD became smaller after exclusion of participants with comorbid agoraphobia and specific phobia, suggesting that these disorders may partly drive the advanced brain-PAD. In conclusion, this ENIGMA-Anxiety mega-analysis did not find evidence of advanced brain ageing in the full sample of adult participants with SAD relative to HCs. However, a sub-analysis suggested that SAD with co-occurring phobic disorders, or the phobic disorders themselves, are associated with neurostructural patterns typical of older brains. Future research could utilise transdiagnostic samples with information on age of onset and disorder duration to further clarify this relation.

Prenatal cannabis use is increasing globally, with estimates up to 35% in North America. Fetal exposure to {Delta}9-tetrahydrocannabinol (THC) has been linked to neurodevelopmental deficits. Yet mechanistic understanding remains limited because animal models incompletely recapitulate human fetal development, and human-relevant in vitro platforms are scarce. To address this gap, we generated human iPSC-derived prefrontal cortex organoids (PFCOs) and used an integrated multi-omics approach combining bulk RNA-seq, whole-genome bisulfite sequencing (WGBS), and electrophysiology to characterize early molecular and functional responses to acute THC exposure at a developmentally relevant stage. THC induced a rapid, transient shift toward excitatory and neurodevelopmental gene expression programs while simultaneously suppressing extracellular matrix and adhesion pathways critical for structural support. Concurrent epigenetic remodeling selectively targeted synaptic assembly, postsynaptic organization, and axonal guidance genes, creating a mismatch between early activation of neuronal programs and epigenetic repression of the scaffolding required for their proper integration. Functionally, these disruptions manifested as delayed but reversible increases in burst duration at 24 hours, indicating altered coordination of network activity. Transcriptional and epigenetic responses converged on autism spectrum disorder (ASD) associated gene networks, with strong enrichment among high-confidence and strong-candidate ASD risk genes, suggesting that THC preferentially perturbs neurodevelopmentally vulnerable pathways. Together, these findings define a mechanistic framework in which THC disrupts early human cortical development through a cycle of transient excitatory activation, compromised structural support, and persistent epigenetic alterations, which are features specifically revealed by human PFCOs.

Childhood-onset obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder with a strong genetic component. De novo variants (DNVs) have been shown to have a role in childhood-onset OCD, but to date, no DNV analysis has been performed in patients from a genetically isolated population. Here, we aimed to investigate the impact of rare de novo single nucleotide variants (dnSNVs) on childhood-onset OCD risk in the French-Canadian population. In a cohort of 36 French-Canadian trios comprised of 36 probands with childhood-onset OCD and 72 unaffected parents, we identified 34 dnSNVs harboured in 34 different genes. We found that four of these genes were previously associated with OCD, replicating their contribution to its risk. We also observed complete overlap between our 34 candidate genes and genes associated with 11 related neuropsychiatric disorders, supporting a shared underlying genetic susceptibility across psychopathologies. Among genes harbouring DNVs across three childhood-onset OCD cohorts, we observed an overrepresentation of genes involved in clathrin-dependent endocytosis (GO:0072583; p-adj = 0.0498) and phosphatidylinositol binding (GO:0035091; p-adj = 0.0431), offering potential biological mechanisms underlying childhood-onset OCD. No association was found between the number of dnSNVs in childhood-onset OCD probands and OCD symptom severity. Altogether, this study offers a framework for performing DNV analyses of complex disorders in genetically isolated populations. We have provided the first list of candidate childhood-onset OCD genes in the French-Canadian population.

Hypothalamic-pituitary-adrenal axis (HPA axis) dysregulation is a risk factor for poor mental and physical health. Animal studies indicate that DNA methylation may be one mechanism through which stress can influence the function of the HPA axis, however human studies have not identified consistent individual loci. Machine learning can be used to develop methylation profile scores (MPSs), but this method has not yet been applied to HPA axis function. Using a novel machine learning pipeline, we developed an MPS to predict the salivary cortisol response (AUCi) to the Trier Social Stress Test (TSST) from whole blood Illumina Infinium HumanMethylation 450K BeadChip data (N = 84, mean age = 34, 49% female). The MPS was associated with the cortisol response in an independent, cross-tissue cohort (N = 53, mean age = 20, 51% female), both before ({beta} = 0.33, 95% CI [0.09, 0.54]) and after a social stressor ({beta} = 0.3, 95% CI [0.09, 0.47]). Functional characterisation revealed several immune, stress, and disease-related pathways and genes, including tolerance induction to self antigen, chronic myeloid leukemia, NR3C2, and PSMB4 (putatively causal in depression). We have developed and validated a novel epigenetic biomarker for stress reactivity, identifying a set of genomic loci where DNA methylation is associated with the cortisol response. Future research could investigate if HPA axis-related MPSs could be used alongside traditional risk factors to improve clinical risk assessment.

Autism spectrum disorder (ASD) is a neurodevelopmental condition associated with altered resting-state brain function. An increased excitation-inhibition (E/I) ratio is discussed as a potential pathomechanism but in-vivo evidence of disturbed neurotransmission underlying these functional alterations remains scarce. We compared rs-fMRI local activity (LCOR) between ASD (N=405, N=395) and neurotypical controls (N=473, N=474) in two independent cohorts (ABIDE1 and ABIDE2). We then tested how these LCOR alterations co-localize with specific neurotransmitter systems derived from nuclear imaging and compared them with E/I changes induced by GABAergic (midazolam) and glutamatergic medication (ketamine). Across both cohorts, ASD subjects consistently exhibited reduced LCOR, particularly in higher-order default mode network nodes, alongside increases in bilateral temporal regions, the cerebellum, and brainstem. These LCOR alterations negatively co-localized with dopaminergic (D1, D2, DAT), glutamatergic (NMDA, mGluR5), GABAergic (GABAa) and cholinergic neurotransmission (VAChT). The NMDA-antagonist ketamine, but not GABAa-potentiator midazolam, induced LCOR changes which co-localize with D1, NMDA and GABAa receptors, thereby resembling alterations observed in ASD. We find consistent local activity alterations in ASD to be spatially associated with several major neurotransmitter systems. NMDA-antagonist ketamine induced neurochemical changes similar to ASD-related alterations, supporting the notion that pharmacological modulation of the E/I balance in healthy individuals can induce ASD-like functional brain changes. These findings provide novel insights into neurophysiological mechanisms underlying ASD. One Sentence SummaryLocal activity alterations in ASD co-localize with glutamatergic and GABAergic neurotransmission and were similar to ketamine-induced brain changes.

BackgroundPreviously, population-based cohort studies have identified the association between epigenetic modifications of OR2L13 related to mental disorders and Gestational diabetes mellitus (GDM). However, the causal nature of these associations remains difficult to establish owing to confounding. AimsThe purpose of the study was to investigate the causal effect of methylation of OR2L13 and offspring mental health outcomes. MethodWe performed two-sample mendelian randomisation to assess the effect of methylation of OR2L13 on mental disorders. Methylation of 7 CpG sites within OR2L13 related to GDM from two previous studies were used as exposure. Genome wide significant single nucleotide polymorphisms for methylation of OR2L13 retrieved from published data were used as instrumental variables. Their causal impact on major psychiatric disorders was assessed using summary-level data mostly from the Psychiatric Genomics Consortium. ResultsLower OR2L13 methylation was casually associated with a higher risk of PD in offspring [cg03748376: odds ratio (OR)=0.81, 95% confidence interval (CI) =0.68-0.97, P =0.02]. However, little evidence was found for a causal relationship between the methylation levels of OR2L13 and autism spectrum disorder (ASD), attention deficit/hyperactivity disorder (ADHD), schizophrenia (SCZ), major depressive disorder (MDD), bipolar disorder (BD) and obsessive-compulsive disorder (OCD). ConclusionsEvidence from our study supported a causal effect of lower OR2L13 methylation on PD risk.