Stephanie Le Hellard

Cognitive-behavioral therapy (CBT) is a widely used treatment for mental disorders, yet the biological mechanisms underlying its effects and the factors contributing to treatment response remain poorly understood. DNA methylation, an epigenetic mechanism shaped by both genetic and environmental influences, may provide insights into individual differences in psychotherapy outcomes. We performed an epigenome-wide association study of psychotherapy response in 889 adults with obsessive-compulsive disorder (OCD) receiving the Bergen 4-Day Treatment, an intensive, concentrated exposure-based intervention. Saliva samples were collected before treatment, immediately after treatment, and at 3-month follow-up. DNA methylation was profiled using the Illumina EPIC v2 array. We identified three classes of differentially methylated regions (DMRs): (1) ten baseline DMRs associated with subsequent treatment response, (2) 23 DMRs showing stable associations with response across time points, and (3) three DMRs exhibiting longitudinal methylation changes associated with response. These loci were annotated to genes involved in neuroplasticity, neurodevelopment, stress response, immune function, mitochondrial processes, and gene regulation. Additional sex-stratified analyses identified several sex-specific DNA methylation signals associated with treatment response. Most baseline and time-stable methylation signals were influenced by genetic variation, whereas longitudinal signals showed no significant local genetic effects. In addition, modest shifts in monocyte and CD4+ T-cell proportions were associated with treatment response. These findings suggest that response to exposure-based psychotherapy in OCD is associated with both trait-like and dynamic peripheral epigenetic variation. Pre-treatment DNA methylation profiles may ultimately help predict treatment outcomes and support future precision psychiatry approaches.

Background: Season at birth has been associated with increased risk for psychotic disorders. Epigenetic markers, which can be influenced by environmental exposures, may help to understand the mechanisms of seasonal effects. Aims: To investigate two types of seasonal influences on DNA methylation: season of sampling and season of birth, and to test whether these seasonal effects interact with psychotic disorder risk. Methods: We used two cohorts: a sample of newborns from the Norwegian Mother, Father, and Child Study (MoBa) and a sample of adult participants from the Thematically Organized Psychosis (TOP) sample. The cosinor function from the R package “seasons” was used to identify seasonally methylated positions (SMPs) associated with season of birth and season of sampling. Meta-analyses were performed between results from the MoBa birth cohort, and the TOP healthy adults samples for both season of birth and season of sampling. Interaction analyses between season of birth/season of sampling and psychosis status were conducted in the TOP cohort. Results: In the meta-analysis of healthy controls from our cohorts, we identified six SMPs (IQSEC1, CACNA2D3, TMEM86B, CNOT3, ZNF250, and ARHGEF3) and two SMPs (ZNF250 and SLC6A19) associated with season of sampling and season of birth, respectively. In the interaction analysis, one significant SMP (cg13593913,) was found to be associated with a psychosis diagnosis and season of birth. Conclusion: In our study, we show a potential interaction between season of birth and psychosis diagnosis. These findings highlight the importance of considering the season of birth and season of sampling in epigenetic research.

Background Antipsychotic drugs (AP) are commonly prescribed for the treatment of psychotic symptoms in schizophrenia (SCZ), bipolar disorder (BP), and major depressive disorder (MDD). However, despite over 70 years of clinical use, the pharmacological mechanisms underlying AP drug action remain incompletely understood. DNA methylation (DNAm) provides a means to investigate epigenetic changes associated with AP exposure and to explore biological pathways potentially involved in AP pharmacology. This study aims to identify DNAm changes associated with treatment using olanzapine, quetiapine, and risperidone which may suggest shared or drug-specific epigenetic signatures. Methods We analysed genome-wide DNAm levels in the blood of 263 psychiatric patients who were treated with AP monotherapies (n = 136, olanzapine n = 89, quetiapine n = 26, risperidone n = 21) or were medication-free (n = 127). We assessed the correlation between DNAm levels and AP serum concentrations of each drug individually and of those shared between the three drugs. To identify drug-specific effects, we compared DNAm profiles between drugs and DNAm levels of medication-free patients. Results We identified 60 CpGs and seven differentially methylated regions (DMRs) consistently associated with all three AP treatments (experiment wide significant threshold p < 6.1 x 10 ^− 8 ), involving genes linked to postsynaptic density regulation in glutamatergic neurons ( SHANK2 ), signal transduction ( GNB1 ), synaptic plasticity ( GAS7 ), and neuronal signalling ( FBXW4 and ZNF471 ). No significant DNAm effects were associated with any specific AP monotherapy. None of the identified effects were among DNAm differences reported in a large EWAS between cases with SCZ and controls. These findings contribute to the characterization of the association between AP treatment and DNAm and provide insights into AP molecular mechanisms of action.

Electroconvulsive therapy (ECT) is an effective antidepressant treatment. The mechanisms behind the therapeutic effect are not fully understood, and reliable biomarkers for response are needed. Epigenetic modifications, such as DNA methylation (DNAm), can reflect both genetic and environmental impacts; they may shed light on the mechanisms behind treatment effects and they have the potential to inform response prediction. We performed an epigenome-wide association study (EWAS) in peripheral blood from patients before and after ECT in a Norwegian cohort (n = 65). The methylation levels of 12 differentially methylated CpG positions (DMPs) and 18 differentially methylated regions (DMRs) were significantly associated with percent clinical response. In addition, 29 DMPs and 23 DMRs were significantly associated with remission (Montgomery and Åsberg Depression Rating Scale MADRS < 10 post treatment). Two DMRs were also significantly associated with percent response at baseline and four DMRs were significantly associated with remission at baseline (FDR < 0.05). We did not identify any longitudinal (pre-post) changes in DNAm. We further performed the first meta-analysis (n = 99) between ECT cohorts, combining this Norwegian cohort and a German ECT cohort (n = 34). Seven of the DMRs found to be associated with response in the meta-analyses were previously identified in the Norwegian or the German cohort (FDR < 0.05). Methylation risk scores (MS) calculated using DMPs associated with ECT in the Norwegian cohort showed promising association with response to ECT in the German cohort (p = 0.06). Finally, we found increased neutrophil to lymphocyte ratios, calculated from estimated cell proportions, to be associated with remission (p < 0.003) in the Norwegian cohort.

Background: The underdiagnosis of Attention-Deficit/Hyperactivity Disorder (ADHD) in females, particularly those with the inattentive presentation, highlights a critical gap in clinical care. Although DNA methylation is often tissue-specific, accessible peripheral tissues like cord blood provide valuable insights into early-life risk and can serve as biomarkers. We aimed to identify sex-specific DNA methylation signatures in cord blood associated with childhood ADHD symptoms, which could illuminate early-life risk markers and inform improved detection strategies. Method: We conducted sex-stratified epigenome-wide association study (EWAS) of cord blood DNA methylation in relation to ADHD symptoms in children (n=2,391; 48.1% females) from the Norwegian Mother, Father, and Child cohort study (MoBa). We tested for sex interaction effects and analyzed inattention and hyperactivity/impulsivity symptoms separately. Results: We identified five differentially methylated CpG positions (DMPs) and 22 differentially methylated regions (DMRs). In females, two DMPs, cg13084029 ( ARRB1 ) and cg15676735 ( ZBTB3 ), and seven DMRs were associated with inattention symptoms. The identified DMPs exhibited significant sex interaction effects (adjusted p -value < 0.05). There was no overlap between the DMPs or DMRs identified in females and males, and the epigenetic signatures for inattention and hyperactivity/impulsivity were largely disparate. Several annotated genes (e.g., ARRB1, PNPO, KDM5B , HOXA2, and HOXC4 ) have recognized roles in neurotransmission and neurodevelopment. Conclusion: Our findings demonstrate that the peripheral DNA methylation signatures at birth associated with later ADHD symptoms are distinct between females and males. This highlights the value of sex-stratified analyses and suggests that peripheral epigenetic profiles hold promise for the development of tools for early detection.

Background: Genetic ancestry is an important factor to account for in DNA methylation studies because genetic variation influences DNA methylation patterns. One approach uses principal components (PCs) calculated from CpG sites that overlap with common SNPs to adjust for ancestry when genotyping data is not available. However, this method does not remove technical and biological variations, such as sex and age, prior to calculating the PCs. The first PC is therefore often associated with factors other than ancestry. Methods: We developed and adapted the adapted EpiAnceR+ approach, which includes (1) residualizing the CpG data overlapping with common SNPs for control probe PCs, sex, age, and cell type proportions to remove the effects of technical and biological factors, and (2) integrating the residualized data with genotype calls from the SNP probes (commonly referred to as rs probes) present on the arrays, before calculating PCs and evaluated the clustering ability and relationship to genetic ancestry. Results: The PCs generated by EpiAnceR+ led to improved clustering for repeated samples from the same individual and stronger associations with genetic ancestry groups predicted from genotype information compared to the original approach. EpiAnceR+ also outperformed the use of DNA methylation PCs or surrogate variables for ancestry adjustment. Conclusions: We show that the EpiAnceR + approach improves the adjustment for genetic ancestry in DNA methylation studies. EpiAnceR+ can be integrated into existing R pipelines for commercial methylation arrays, such as 450 K, EPIC v1, and EPIC v2. The code is available on GitHub ( https://github.com/KiraHoeffler/EpiAnceR ).

Background: Obsessive-compulsive disorder (OCD) is a debilitating psychiatric condition influenced by both genetic and environmental risk factors. Epigenetic modifications, such as DNA methylation, may offer insights into biologically meaningful differences associated with the disorder. Methods: We conducted the largest methylome-wide association study (MWAS) of OCD to date, analyzing saliva DNA samples from 414 individuals with OCD and 384 controls using the Illumina EPICv2 array. Differentially methylated positions (DMPs) and regions (DMRs) were identified, with additional analyses including sex-stratified comparisons, methylation quantitative trait loci (mQTL) mapping, and assessments of cell-type composition differences. Results: We identified 35 DMPs and 17 DMRs associated with OCD, mapping to genes involved in neurotransmission, neurodevelopment, synaptic function, and gene regulation. Sex-stratified analyses revealed additional sex-specific methylation signals, highlighting biological differences between males and females. Most associated loci were influenced by genetic variation (mQTLs). Differences in estimated cell composition and the identification of immune-related genes suggest a potential role for immune system processes. Correlation analyses between brain and saliva methylation indicated that several findings may reflect brain-relevant biology. Conclusions: Our findings emphasize the importance of integrating epigenetic, genetic, and sex-specific data to advance our understanding of OCD. DNA methylation may ultimately contribute to progress toward clinically relevant precision medicine approaches.