Genetic variants linked to autism are thought to change cognition and behaviour by altering the structure and function of the brain. Although a substantial body of literature has identified structural brain differences in autism, it is unknown whether autism-associated common genetic variants are linked to changes in cortical macro- and micro-structure. We investigated this using neuroimaging and genetic data from adults (UK Biobank, N = 31,748) and children (ABCD, N = 4928). Using polygenic scores and genetic correlations we observe a robust negative association between common variants for autism and a magnetic resonance imaging derived phenotype for neurite density (intracellular volume fraction) in the general population. This result is consistent across both children and adults, in both the cortex and in white matter tracts, and confirmed using polygenic scores and genetic correlations. There were no sex differences in this association. Mendelian randomisation analyses provide no evidence for a causal relationship between autism and intracellular volume fraction, although this should be revisited using better powered instruments. Overall, this study provides evidence for shared common variant genetics between autism and cortical neurite density.

Bipolar disorder is a leading contributor to the global burden of disease1. Despite high heritability (60-80%), the majority of the underlying genetic determinants remain unknown2. We analysed data from participants of European, East Asian, African American and Latino ancestries (n = 158,036 cases with bipolar disorder, 2.8 million controls), combining clinical, community and self-reported samples. We identified 298 genome-wide significant loci in the multi-ancestry meta-analysis, a fourfold increase over previous findings3, and identified an ancestry-specific association in the East Asian cohort. Integrating results from fine-mapping and other variant-to-gene mapping approaches identified 36 credible genes in the aetiology of bipolar disorder. Genes prioritized through fine-mapping were enriched for ultra-rare damaging missense and protein-truncating variations in cases with bipolar disorder4, highlighting convergence of common and rare variant signals. We report differences in the genetic architecture of bipolar disorder depending on the source of patient ascertainment and on bipolar disorder subtype (type I or type II). Several analyses implicate specific cell types in the pathophysiology of bipolar disorder, including GABAergic interneurons and medium spiny neurons. Together, these analyses provide additional insights into the genetic architecture and biological underpinnings of bipolar disorder.

Peptide antibodies are particularly useful for immunocytochemistry (ICC) and immunohistochemistry (IHC), where antigens may denature due to fixation of tissues and cells. Peptide antibodies can be made to any defined sequence, including unknown putative proteins and posttranslationally modified sequences. Moreover, the availability of large amounts of the antigen (peptide) allows inhibition/absorption controls, which are important in ICC/IHC, due to the many possibilities for false-positive reactions caused by immunoglobulin Fc receptors, nonspecific reactions and cross-reactivity of primary and secondary antibodies with other antigens and endogenous immunoglobulins, respectively. Here, simple protocols for ICC and IHC are described together with recommendations for appropriate controls.

Post-traumatic stress disorder (PTSD) genetics are characterized by lower discoverability than most other psychiatric disorders. The contribution to biological understanding from previous genetic studies has thus been limited. We performed a multi-ancestry meta-analysis of genome-wide association studies across 1,222,882 individuals of European ancestry (137,136 cases) and 58,051 admixed individuals with African and Native American ancestry (13,624 cases). We identified 95 genome-wide significant loci (80 new). Convergent multi-omic approaches identified 43 potential causal genes, broadly classified as neurotransmitter and ion channel synaptic modulators (for example, GRIA1, GRM8 and CACNA1E), developmental, axon guidance and transcription factors (for example, FOXP2, EFNA5 and DCC), synaptic structure and function genes (for example, PCLO, NCAM1 and PDE4B) and endocrine or immune regulators (for example, ESR1, TRAF3 and TANK). Additional top genes influence stress, immune, fear and threat-related processes, previously hypothesized to underlie PTSD neurobiology. These findings strengthen our understanding of neurobiological systems relevant to PTSD pathophysiology, while also opening new areas for investigation. Multi-ancestry genome-wide analyses identify 95 loci associated with post-traumatic stress disorder and implicate candidate genes, pathways and neurobiological systems underlying its pathophysiology.

BACKGROUND:The association between intra-uterine exposure to maternal smoking and risk of multiple sclerosis (MS) has been little studied and with conflicting results.OBJECTIVE:To examine the risk of MS in offspring exposed intra-uterine to maternal smoking. In addition, to re-examine prior observations of an elevated risk of MS among smokers, assuming that self-reported smoking during pregnancy reflects the woman's general smoking habits.METHODS:The study cohort included all Danish women, pregnant in the period 1991-2018, (n = 789,299) and singletons from these pregnancies (n = 879,135). Nationwide information on maternal smoking during pregnancy and MS cases in the study cohort were obtained from the Medical Birth Register and the National Patient Register. Cox regression analysis was used to estimate hazard ratios (HRs) for the association between smoking and MS risk.RESULTS:Women who smoked during pregnancy had a 42% increased risk of developing MS compared with non-smoking women (HR = 1.42 (1.32-1.52), n = 1,296). The risk of MS among singletons of women who smoked during pregnancy was 38% higher than that among singletons born to non-smoking women (HR = 1.38 (1.08-1.76), n = 110).CONCLUSION:Our observations add further to the evidence implicating smoking in the development of MS and suggest that intra-uterine exposure to tobacco smoke may increase MS risk.

Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder typically detected in childhood. Although ADHD has been demonstrated to have a strong genetic component, environmental risk factors, such as maternal infections during pregnancy, may also play a role. We therefore measured the immunological response to 5 abundant microorganisms (Toxoplasmosis Gondii, cytomegalovirus (CMV), Herpes Simplex Virus 1, Epstein Barr Virus and mycoplasma pneumoniae) in newborn heel prick samples of 1679 ADHD cases and 2948 matching controls as part of the iPSYCH Danish case-cohort study. We found an association between high antiCMV (OR 1.30, 95 % CI [1.09,1.55], p = 0.015) and anti-mycoplasma (OR 1.30, 95 % CI [1.07,1.59], p = 0.037) signal and those newborns later being diagnosed with ADHD. The risk estimate remained increased when controlling for ADHD polygenic risk score as well as penicillin prescriptions. We saw a dose-response association with the amount of positive anti-microorganism titers increasing the risk of being diagnosed with ADHD later in life (p = 0.01 for the trend), suggesting that the more activated the immune system is prior to or at birth, the higher the risk is for a later diagnosis with ADHD. If the associations are causal, they emphasize the importance of a healthy life style during pregnancy to reduce the risk of infections when pregnant and the associated risks for the child.

Cannabis use disorder (CUD) and cannabis use (CU) are prevalent conditions co-occurring with attention-deficit hyperactivity disorder (ADHD). Here we report results from a cross-disorder genome-wide association study of ADHD and CUD or CU. We identified 36 concordant genome-wide significant loci for ADHD-CUD and ten loci for ADHD-CU. DRD2 was identified as an ADHD-CUD risk gene. ADHD-CUD risk genes showed high expression across brain tissues and brain developmental stages, which was not observed for ADHD-CU genes. ADHD-CUD and ADHD-CU showed similar genetic correlations with substance use, whereas they differed for substance-use disorders. Individuals with ADHD-CUD had increased polygenic scores (PGS) for psychiatric disorders compared with those with ADHD without CUD and increased burden of rare deleterious variants. Stratification of individuals with ADHD by their CUD PGS revealed an absolute risk of 22% for comorbid CUD in the highest CUD-PGS bin-much higher than 1.6% risk among controls. Sex-specific differences were substantial with an approximately 10% higher CUD risk among men in the highest CUD-PGS bin.

Background:Neonatal herpes simplex virus (HSV) infection is life-threatening, with a mortality of up to 70-80% when disseminated, often due to vague symptoms and delayed treatment. Neonatal screening using dried blood spot (DBS) samples is among the most impactful preventative health measures ever implemented, but screening for HSV has not been investigated.Methods:We investigated high throughput multiplexed proteomics on DBS samples collected on days 2-3 of life from a nationwide cohort of neonates with HSV infection (n = 53) and matched controls. We measured 2941 proteins using the Olink Explore 3072 panels and proximity extension assays, followed by differential protein expression by Analysis of Variance with post-hoc correction and functional annotation.Results:Here, we show distinct protein profiles in neonates with disseminated HSV disease, with differences in 20 proteins compared to controls. These proteins are associated with innate and adaptive immune responses and cytokine activation.Conclusions:Our findings indicate the potential of neonatal screening for disseminated HSV disease to ensure early treatment and reduce the high mortality.

Importance Recurrent copy number variants (rCNVs) have been associated with increased risk of psychiatric disorders in case-control studies, but their population-level impact is unknown. Objective To provide unbiased population-based estimates of prevalence and risk associated with psychiatric disorders for rCNVs and to compare risks across outcomes, rCNV dosage type (deletions or duplications), and locus features. Design, Setting, and Participants This genetic association study is an analysis of data from the Lundbeck Foundation Initiative for Integrative Psychiatric Research (iPSYCH) case-cohort sample of individuals born in Denmark in 1981-2008 and followed up until 2015, including (1) all individuals (n = 92 531) with a hospital discharge diagnosis of attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), bipolar disorder, major depressive disorder (MDD), or schizophrenia spectrum disorder (SSD) and (2) a subcohort (n = 50 625) randomly drawn from the source population. Data were analyzed from January 2021 to August 2023. Exposures Carrier status of deletions and duplications at 27 autosomal rCNV loci was determined from neonatal blood samples genotyped on single-nucleotide variant microarrays. Main Outcomes and MeasuresPopulation-based rCNV prevalence was estimated with a survey model using finite population correction to account for oversampling of cases. Hazard ratio (HR) estimates and 95% CIs for psychiatric disorders were derived using weighted Cox proportional hazard models. Risks were compared across outcomes, dosage type, and locus features using generalized estimating equation models. Results A total of 3547 rCNVs were identified in 64 735 individuals assigned male at birth (53.8%) and 55 512 individuals assigned female at birth (46.2%) whose age at the end of follow-up ranged from 7.0 to 34.7 years (mean, 21.8 years). Most observed increases in rCNV-associated risk for ADHD, ASD, or SSD were moderate, and risk estimates were highly correlated across these disorders. Notable exceptions included high ASD-associated risk observed for Prader-Willi/Angelman syndrome duplications (HR, 20.8; 95% CI, 7.9-55). No rCNV was associated with increased MDD risk. Also, rCNV-associated risk was positively correlated with locus size and gene constraint but not with dosage type. Comparison with published case-control and community-based studies revealed a higher prevalence of deletions and lower associated increase in risk for several rCNVs in iPSYCH2015. Conclusions and Relevance This study found that several rCNVs were more prevalent and conferred less risk of psychiatric disorders than estimated previously. Most case-control studies overestimate rCNV-associated risk of psychiatric disorders, likely because of selection bias. In an era where genetics is increasingly being clinically applied, these results highlight the importance of population-based risk estimates for genetics-based predictions.

The prevalence of autism in Denmark has been increasing, reaching 1.65

Background: Bilirubin has antioxidant properties, and elevated levels within the normal range have been associated with improved lung function and decreased risk of asthma in adults, but studies of young children are scarce. Here, we investigate associations between bilirubin in early life and respiratory health endpoints during preschool age in two independent birth cohorts. Methods: Bilirubin metabolites were assessed at ages 0.5, 1.5, and 6 years in COPSAC(2010) (Copenhagen Prospective Studies on Asthma in Childhood 2010) and ages 1, 3, and 6 years in the VDAART (The Vitamin D Antenatal Asthma Reduction Trial) cohort. Meta-analyses were done to summarize the relationship between levels of bilirubin metabolites and asthma, infections, lung function, and allergic sensitization until age 6 across the cohorts. Interaction with the glucuronosyltransferase family 1 member A1 (UGT1A) genotype encoding for an enzyme in the bilirubin metabolism was explored, and metabolomics data were integrated to study underlying mechanisms. Findings: Increasing bilirubin (Z,Z) at ages 1.5-3 years was associated with an increased risk of allergic sensitization (adjusted relative risk [aRR] = 1.85 [1.20-2.85], p = 0.005), and age 6 bilirubin (Z,Z) also showed a trend of association with allergic sensitization at age 6 (aRR =1.31 [0.97-1.77], p = 0.08), which showed significant interaction for the age 6 bilirubin (Z,Z)xUGT1A genotype. Further, increasing bilirubin (E,E), bilirubin (Z,Z), and biliverdin at ages 1.5-3 years was associated with a lower forced expiratory volume at age 6 (aRR range = 0.81-0.91, p < 0.049) but without a significant interaction with the UGT1A genotype (p interactions > 0.05). Network analysis showed a significant correlation between bilirubin metabolism and acyl carnitines. There were no associations between bilirubin metabolites and the risk of asthma and infections. Conclusions: Bilirubin metabolism in early life may play a role in childhood respiratory health, particularly in children with specific UGT1A genotypes. Funding: The Lundbeck Foundation (Grant no R16-A1694), The Ministry of Health (Grant no 903516), Danish Council for Strategic Research (Grant no 0603-00280B), and The Capital Region Research Foundation have provided core support to the COPSAC research center. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 946228). The Vitamin D Antenatal Asthma Reduction Trial (VDDART, ClinicalTrials.gov identifier: NCT00920621) was supported by grant U01HL091528 from NHLBI, U54TR001012 from the National Centers for Advancing Translational Sciences (NCATS). Metabolomics work by VDAART was supported by the National Heart, Lung, and Blood Institute (NHLBI) grant R01HL123915 and R01HL141826. S.T.W. was supported by R01HL091528 from the NHLBI, UG3OD023268 from Office of The Director, National Institute of Health, and P01HL132825 from the NHLBI.

Complement components have been linked to schizophrenia and autoimmune disorders. We examined the association between neonatal circulating C3 and C4 protein concentrations in 68,768 neonates and the risk of six mental disorders. We completed genome-wide association studies (GWASs) for C3 and C4 and applied the summary statistics in Mendelian randomization and phenome-wide association studies related to mental and autoimmune disorders. The GWASs for C3 and C4 protein concentrations identified 15 and 36 independent loci, respectively. We found no associations between neonatal C3 and C4 concentrations and mental disorders in the total sample (both sexes combined); however, post-hoc analyses found that a higher C3 concentration was associated with a reduced risk of schizophrenia in females. Mendelian randomization based on C4 summary statistics found an altered risk of five types of autoimmune disorders. Our study adds to our understanding of the associations between C3 and C4 concentrations and subsequent mental and autoimmune disorders.

Sample recruitment for research consortia, biobanks, and personal genomics companies span years, necessitating genotyping in batches, using different technologies. As marker content on genotyping arrays varies, integrating such datasets is non-trivial and its impact on haplotype estimation (phasing) and whole genome imputation, necessary steps for complex trait analysis, remains under-evaluated. Using the iPSYCH dataset, comprising 130,438 individuals, genotyped in two stages, on different arrays, we evaluated phasing and imputation performance across multiple phasing methods and data integration protocols. While phasing accuracy varied by choice of method and data integration protocol, imputation accuracy varied mostly between data integration protocols. We demonstrate an attenuation in imputation accuracy within samples of non-European origin, highlighting challenges to studying complex traits in diverse populations. Finally, imputation errors can bias association tests, reduce predictive utility of polygenic scores. Carefully optimized data integration strategies enhance accuracy and replicability of complex trait analyses in complex biobanks.

Attention-deficit / hyperactivity disorder (ADHD) is a neurodevelopmental disorder with well established associations with pregnancy outcomes. We hypothesised that transcriptomic profiles at birth capture in-utero exposures in addition to genetic factors that are responsible for the onset of ADHD symptoms later in life. To test our hypothesis, we sequenced RNA from blood which had been kept in storage by being transferred to filter paper, dried, and stored at -20°C for up to 39 years. We sequenced RNA from 305 twin-pairs, 38 of whom have a concordant ADHD diagnosis, and 120 of whom have a discordant ADHD diagnosis, according to data from Danish registers. After ensuring that data obtained from DBS is of sufficient quality to perform downstream analysis, we tested for differential expression between cases and controls, and performed pathway analysis on genes we found to be significantly differentially expressed. We found there is no loss of resolution in RNA-seq data obtained from DBS samples, and that we can successfully correct for bias due to non-random transcript degradation by using principal components. Genes which were differentially expressed in individuals who developed ADHD were primarily expressed in platelets and cerebellar tissue, and were involved in immune system response, cell-binding, and signalling. By sequencing RNA from decade-old blood, we could successfully establish clear differences in the transcriptomic profiles of individuals diagnosed with ADHD later in life. This potentially paves the way for the discovery of biomarkers present at birth which are indicative of an increased risk of developing ADHD later on in life.

Posttraumatic stress disorder (PTSD) genetics are characterized by lower discoverability than most other psychiatric disorders. The contribution to biological understanding from previous genetic studies has thus been limited. We performed a multi-ancestry meta-analysis of genome-wide association studies across 1,222,882 individuals of European ancestry (137,136 cases) and 58,051 admixed individuals with African and Native American ancestry (13,624 cases). We identified 95 genome-wide significant loci (80 novel). Convergent multi-omic approaches identified 43 potential causal genes, broadly classified as neurotransmitter and ion channel synaptic modulators (e.g., GRIA1, GRM8, CACNA1E ), developmental, axon guidance, and transcription factors (e.g., FOXP2, EFNA5, DCC ), synaptic structure and function genes (e.g., PCLO, NCAM1, PDE4B ), and endocrine or immune regulators (e.g., ESR1, TRAF3, TANK ). Additional top genes influence stress, immune, fear, and threat-related processes, previously hypothesized to underlie PTSD neurobiology. These findings strengthen our understanding of neurobiological systems relevant to PTSD pathophysiology, while also opening new areas for investigation.

Cognitive functions of individuals with psychiatric disorders differ from that of the general population. Such cognitive differences often manifest early in life as differential school performance and have a strong genetic basis. Here we measured genetic predictors of school performance in 30,982 individuals in English, Danish and mathematics via a genome-wide association study (GWAS) and studied their relationship with risk for six major psychiatric disorders. When decomposing the school performance into math and language-specific performances, we observed phenotypically and genetically a strong negative correlation between math performance and risk for most psychiatric disorders. But language performance correlated positively with risk for certain disorders, especially schizophrenia, which we replicate in an independent sample (n = 4547). We also found that the genetic variants relating to increased risk for schizophrenia and better language performance are overrepresented in individuals involved in creative professions (n = 2953) compared to the general population (n = 164,622). The findings together suggest that language ability, creativity and psychopathology might stem from overlapping genetic roots.

Biobank research may lead to an improved understanding of disease etiology and advance personalized medicine. Denmark (population ~5.9 million) provides a unique setting for population-based health research. The country is a rich source of biobanks and the universal, tax-funded healthcare system delivers routinely collected data to numerous registries and databases. By virtue of the civil registration number (assigned uniquely to all Danish citizens), biological specimens stored in biobanks can be combined with clinical and demographic data from these population-based health registries and databases. In this review, we aim to provide an understanding of advantages and possibilities of biobank research in Denmark. As knowledge about the Danish setting is needed to grasp the full potential, we first introduce the Danish healthcare system, the Civil Registration System, the population-based registries, and the interface with biobanks. We then describe the biobank infrastructures, comprising the Danish National Biobank Initiative, the Bio- and Genome Bank Denmark, and the Danish National Genome Center. Further, we briefly provide an overview of fourteen selected biobanks, including: The Danish Newborn Screening Biobank; The Danish National Birth Cohort; The Danish Twin Registry Biobank; Diet, Cancer and Health; Diet, Cancer and Health - Next generations; Danish Centre for Strategic Research in Type 2 Diabetes; Vejle Diabetes Biobank; The Copenhagen Hospital Biobank; The Copenhagen City Heart Study; The Copenhagen General Population Study; The Danish Cancer Biobank; The Danish Rheumatological Biobank; The Danish Blood Donor Study; and The Danish Pathology Databank. Last, we inform on practical aspects, such as data access, and discuss future implications.

Genome-wide association studies (GWAS) of cocaine use disorder (CocUD) have been small by current standards, with most analyses having relied on data from the Yale-Penn sample. GWAS discovery for other substance use disorders (SUDs) has been foundational in understanding the genetic and biological components of SUD risk. Although cocaine is one of the most used and addictive illicit drugs in the United States, our biological understanding of CocUD is limited, and not well informed from genetics data. We address this by conducting the largest GWAS of CocUD to date in individuals of African (AFR) and European (EUR) ancestry. The meta-analysis included only new GWAS analyses, and included cohorts from the Million Veteran Program, Yale-Penn, iPSYCH, and BioVU. The AFR meta-analysis included 117,627 individuals (Ncase=22,163) and the EUR meta-analysis consisted of 441,591 subjects (Ncase=14,909) yielding a total sample of 574,127 subjects (Total Ncase=37,072). GWAS were combined using an effective sample-size weighted meta-analysis. Ancestry-specific and cross-ancestry meta-analyses were performed followed by in silico analyses. In the EUR meta-analysis, 27 variants reached genome-wide significance (GWS; p=5.00e-08) mapping to a single locus at DRD2 on chromosome 11 (lead SNP: rs11214607; p=1.02e-11). The AFR meta-analysis resulted in 3 GWS loci; the top AFR association was with rs10467348 (p=7.58e-09) in HS6ST3 on chromosome 13. The cross-ancestry meta-analysis yielded 11 GWS loci; the top cross-ancestry association was with rs2471851 (p=2.65e-12) in DRD2. Gene-set and tissue expression analyses identified processes involved in neurosynaptic functioning and showed enrichment in brain tissue. We conducted the largest GWAS of CocUD to date, substantially advancing CocUD genetic discovery and identifying multiple novel findings including DRD2 that has now been identified across multiple SUDs. This effort advances our understanding of the genetic architecture of CocUD and holds promise for understanding the neurobiology of CocUD and its relationship with other traits.