Publications by authors named "David Hougaard"

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.

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  • Tic disorders (TD) can significantly affect individuals and society, and understanding their genetic causes could lead to better treatments, as family history is a key risk factor.
  • A large-scale GWAS meta-analysis was conducted with nearly 10,000 TD cases and over 981,000 controls, revealing a significant genetic association, though it couldn't be replicated in another study.
  • The findings suggest a complex genetic landscape for TD, highlighting certain genes and brain regions involved, but additional research is needed to firmly establish reliable genetic links.
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  • - ADHD is a neurodevelopmental disorder often identified in childhood, with both genetic and environmental risk factors influencing its development, including maternal infections during pregnancy.
  • - A study measuring immune responses to various microorganisms in newborns found a significant association between higher antibody levels against cytomegalovirus (CMV) and mycoplasma with later ADHD diagnosis.
  • - There is a suggested dose-response relationship indicating that increased immune system activation before or at birth may elevate the risk of ADHD, highlighting the need for healthy pregnancy practices to minimize infection risks.
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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.

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  • The prevalence of autism in Denmark is rising, affecting 1.65% of 10-year-olds, with a focus on understanding its molecular causes through neonatal metabolomics of dried blood spots.
  • Researchers analyzed metabolomic profiles from over 1,400 newborns later diagnosed with autism, identifying over 800 metabolite features using advanced mass spectrometry techniques.
  • Key findings include two metabolites, cyclo-leucine-proline and 5-aminovaleric acid betaine (5-AVAB), which are associated with increased autism risk and could serve as early biomarkers, with 5-AVAB also linked to dietary habits and certain genetic variants.
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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.

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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.

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  • Obsessive-compulsive disorder (OCD) affects about 1% of people and has a strong genetic component, but previous studies have not fully explained its genetic causes or biological mechanisms.
  • A large genome-wide association study (GWAS) analyzed data from over 53,000 OCD cases and over 2 million control participants, identifying 30 significant genetic markers related to OCD and suggesting a 6.7% heritability from SNPs.
  • The research also found 249 candidate risk genes linked to OCD, particularly in specific brain regions, and showed genetic correlations with various psychiatric disorders, laying the groundwork for further studies and potential treatments.
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  • PTSD genetics have been difficult to study compared to other psychiatric disorders, limiting our biological understanding of the condition.
  • A large-scale meta-analysis involving over 1.2 million individuals identified 95 genome-wide significant loci, with 80 being new discoveries related to PTSD.
  • Researchers identified 43 potential causal genes linked to neurotransmitter activity, developmental processes, synaptic function, and immune regulation, enhancing our knowledge of the neurobiological systems involved in PTSD.
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  • Four GWAS studies on obsessive-compulsive disorder (OCD) have been conducted, showing a SNP-heritability of 28% but revealing only one significant SNP so far.
  • A new meta-analysis significantly increased the sample size to analyze 37,015 OCD cases against 948,616 controls, identifying 15 independent genome-wide significant loci, 14 of which were novel.
  • The research highlighted genetic correlations between OCD and various psychiatric disorders, while also mapping the genetic basis and biological pathways associated with OCD susceptibility.
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  • - The study investigated the link between neonatal levels of complement proteins C3 and C4 and the risk of six mental disorders in a large sample of 68,768 newborns.
  • - Genome-wide association studies (GWAS) identified multiple genetic loci related to C3 and C4 concentrations, but overall, no major associations with mental disorders were found in the total sample.
  • - A notable finding was that higher C3 levels were linked to a lower risk of schizophrenia specifically in females, and C4 was associated with altered risk for five autoimmune disorders through Mendelian randomization.
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Problematic alcohol use (PAU), a trait that combines alcohol use disorder and alcohol-related problems assessed with a questionnaire, is a leading cause of death and morbidity worldwide. Here we conducted a large cross-ancestry meta-analysis of PAU in 1,079,947 individuals (European, N = 903,147; African, N = 122,571; Latin American, N = 38,962; East Asian, N = 13,551; and South Asian, N = 1,716 ancestries). We observed a high degree of cross-ancestral similarity in the genetic architecture of PAU and identified 110 independent risk variants in within- and cross-ancestry analyses.

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Attention deficit hyperactivity disorder (ADHD) is a complex disorder that manifests variability in long-term outcomes and clinical presentations. The genetic contributions to such heterogeneity are not well understood. Here we show several genetic links to clinical heterogeneity in ADHD in a case-only study of 14,084 diagnosed individuals.

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As recreational use of cannabis is being decriminalized in many places and medical use widely sanctioned, there are growing concerns about increases in cannabis use disorder (CanUD), which is associated with numerous medical comorbidities. Here we performed a genome-wide association study of CanUD in the Million Veteran Program (MVP), followed by meta-analysis in 1,054,365 individuals (n = 64,314) from four broad ancestries designated by the reference panel used for assignment (European n = 886,025, African n = 123,208, admixed American n = 38,289 and East Asian n = 6,843). Population-specific methods were applied to calculate single nucleotide polymorphism-based heritability within each ancestry.

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  • The study investigates the link between maternal smoking during pregnancy and the risk of multiple sclerosis (MS) in their offspring, an area that has seen limited and inconsistent research.
  • An analysis of data from 789,299 Danish women who were pregnant between 1991 and 2018 revealed that maternal smoking increases the risk of developing MS, with a 42% higher risk for mothers and a 38% higher risk for their children compared to non-smokers.
  • The findings suggest that smoking during pregnancy may contribute to the development of MS, highlighting the importance of addressing smoking in prenatal care to potentially reduce MS risk.
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It remains inconclusive whether postpartum depression (PPD) and depression with onset outside the postpartum period (MDD) are genetically distinct disorders. We aimed to investigate whether polygenic risk scores (PGSs) for major mental disorders differ between PPD cases and MDD cases in a nested case-control study of 50,057 women born from 1981 to 1997 in the iPSYCH2015 sample in Demark. We identified 333 women with first-onset postpartum depression (PPD group), who were matched with 993 women with first-onset depression diagnosed outside of postpartum (MDD group), and 999 female population controls.

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Recurrent copy number variants (rCNVs) are associated with increased risk of neuropsychiatric disorders but their pathogenic population-level impact is unknown. We provide population-based estimates of rCNV-associated risk of neuropsychiatric disorders for 34 rCNVs in the iPSYCH2015 case-cohort sample (n=120,247). Most observed significant increases in rCNV-associated risk for ADHD, autism or schizophrenia were moderate (HR:1.

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Background: We quantified relative and absolute risks of postpartum psychiatric episodes (PPE) following risk factors: Young age, past personal or family history of psychiatric disorders, and genetic liability.

Methods: We conducted a register-based study using the iPSYCH2012 case-cohort sample. Exposures were personal history of psychiatric episodes prior to childbirth, being a young mother (giving birth before the age of 21.

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  • A healthy placenta is crucial for both the mother and fetus during pregnancy, and this study uses placental weight as a measure of its growth.
  • Genome-wide analyses across the genomes of mothers, fathers, and fetuses identified 40 genetic signals related to placental weight, revealing a mix of influences from both parents and the fetus.
  • The findings suggest that higher placental weight, driven by fetal genetics, is linked to an increased risk of preeclampsia and shorter pregnancy duration, highlighting the role of fetal insulin in regulating placental growth.
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  • PTSD genetics are harder to study compared to other mental health disorders, resulting in limited biological insights from past research.
  • A large-scale analysis involving over 1.2 million individuals found 95 significant genetic loci related to PTSD, with 80 being new discoveries.
  • The study identified 43 potential causal genes linked to neurotransmitters, synaptic function, and immune responses, enhancing understanding of PTSD's biological mechanisms and suggesting new research directions.
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Proportional hazards models have been proposed to analyse time-to-event phenotypes in genome-wide association studies (GWAS). However, little is known about the ability of proportional hazards models to identify genetic associations under different generative models and when ascertainment is present. Here we propose the age-dependent liability threshold (ADuLT) model as an alternative to a Cox regression based GWAS, here represented by SPACox.

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  • The accuracy of polygenic scores (PGS) improves significantly with larger sample sizes, which can be difficult to obtain, but using genetically related traits can help expand these samples.
  • The study introduces a new method for creating multi-PGS from existing genome-wide association studies (GWAS) without needing to pick the most relevant studies individually.
  • The multi-PGS framework shows enhanced prediction accuracy, achieving up to a 9-fold increase for certain psychiatric disorders, and can also be applied to new biobanks and traits lacking prior GWAS data.
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