Gender differences in associations of glutamate decarboxylase 1 gene (GAD1) variants with panic disorder

Association of GAD1 gene polymorphism rs3749034 with the information processing and cognitive event-related potentials in schizophrenia patients and healthy subjects

OBJECTIVE

Glutamic acid decarboxylase, an enzyme in GABA biosynthesis, is encoded by the GAD1 gene, the transcriptional activity of which is affected by the rs3749034 polymorphism. The aim was to investigate the effects of rs3749034 on cognitive event-related potentials (P300) in healthy subjects and schizophrenic patients.

METHODS

Determination of rs3749034 polymorphism was performed in 89 healthy volunteers and 109 schizophrenic patients (males). Two-stimulus oddball task performance and P300 auditory evoked potentials were analyzed and patient symptomatology was assessed using the Positive and Negative Syndrome Scale (PANSS).

RESULTS

An increased frequency of C allele carriers was disclosed in patients. In controls, superior task performance was observed in cytosine-thymine carriers, while a greater P300 amplitude and shorter latency were found in C/C carriers. Analogous effects were found in patients with a disease onset before 25 years of age. Higher N5 and lower P3 and G5 PANSS scales were revealed in C/C homozygotes.

CONCLUSIONS

The findings substantiate an involvement of GABA-ergic mechanisms in maintaining an optimal excitatory-inhibitory balance and an association of rs3749034 with early-onset disorder and negative symptoms of schizophrenia.

SIGNIFICANCE

These results are important for understanding underlying mechanisms and the development of evidence-based methods for assessing the risk of schizophrenia.

Glutamate decarboxylase 1 gene polymorphisms are associated with respiratory symptoms in panic disorder

BACKGROUND

Genetic factors play an important role in the pathogenesis of panic disorder (PD). However, the effect of genetic variants on PD remains controversial.

AIM

To evaluate the associations between glutamate decarboxylase 1 (GAD1) gene polymorphisms and PD risk and assess the effect of GAD1 gene polymorphisms on the severity of clinical symptoms in PD.

METHODS

We recruited 230 PD patients and 224 healthy controls in this study. All participants were assessed for anxiety and panic symptom severity using the Hamilton Anxiety Rating Scale (HAM-A) and Panic Disorder Severity Scale (PDSS). GAD1 gene polymorphisms (rs1978340 and rs3749034) were genotyped and assessed for allele frequencies.

RESULTS

There were no significant differences between cases and controls in the genotype distributions or allele frequencies of GAD1 (rs1978340 and rs3749034). In addition, the effect of GAD1 (rs1978340 and rs3749034) on PD severity was not significant. However, regarding respiratory symptoms, patients with the GAD1 rs1978340 A/A genotype had significantly higher scores than those with the A/G or G/G genotype.

CONCLUSION

Here, we showed that the A/A genotype of GAD1 rs1978340 was associated with increased severity of respiratory symptoms in patients with PD.

Phenylbenzothiazole derivatives: effects against a Trypanosoma cruzi infection and toxicological profiles

Current treatments for Chagas disease have a limited impact during the chronic stage and trigger severe side effects. Treatments target Trypanosoma cruzi, the etiological agent of the disease. The aims of this study were to evaluate the trypanocidal activity of four 2-phenylbenzothiazole derivatives (BZT1-4) in vitro by using the infectious and non-infectious forms of T. cruzi (trypomastigotes and epimastigotes, respectively) and to test the most promising compound (BZT4) in vivo in mice. Additionally, the toxicological profile and possible neuronal damage were examined. In relation to trypomastigotes, BZT4 was more selective and effective than the reference drug (benznidazole) during this infective stage, apparently due to the synergistic action of the CF₃ and COOH substituents in the molecule. During the first few hours post-administration of BZT4, parasitemia decreased by 40% in an in vivo model of short-term treatment, but parasite levels later returned to the basal state. In the long-term assessment, the compound did not produce a significant antiparasitic effect, only attaining a 30% reduction in parasitemia by day 20 with the dose of 16 mg/kg. The toxicity test was based on repeated dosing of BZT4 (administered orally) during 21 days, which did not cause liver damage. However, the compound altered the concentration of proteins and the proteinic profile of neuronal cells in vitro, perhaps leading to an effect on the central nervous system. Further research on the low trypanocidal activity in vivo compared to the better in vitro effect could possibly facilitate molecular redesign to improve trypanocidal activity.

Genetic Biomarkers of Panic Disorder: A Systematic Review

(1) Background: Although panic disorder (PD) is one of the most common anxiety disorders severely impacting quality of life, no effective genetic testing exists; known data on possible genetic biomarkers is often scattered and unsystematic which complicates further studies. (2) Methods: We used PathwayStudio 12.3 (Elsevier, The Netherlands) to acquire literature data for further manual review and analysis. 229 articles were extracted, 55 articles reporting associations, and 32 articles reporting no associations were finally selected. (3) Results: We provide exhaustive information on genetic biomarkers associated with PD known in the scientific literature. Data is presented in two tables. Genes COMT and SLC6A4 may be considered the most promising for PD diagnostic to date. (4) Conclusions: This review illustrates current progress in association studies of PD and may indicate possible molecular mechanisms of its pathogenesis. This is a possible basis for data analysis, novel experimental studies, or developing test systems and personalized treatment approaches.

Allergic rhinitis increases the risk of incident panic disorder among young individuals: A nationwide population-based cohort study in Taiwan

BACKGROUND

Studies have reported an association between allergy and panic disorder. However, few studies have explored the relationship between allergic rhinitis and panic disorder. Previous studies were limited by cross-sectional study designs, self-reported symptoms, absence of matched controls, and lack of consideration of the influence of steroid and comorbidities. This study aimed to explore the longitudinal association between allergic rhinitis and panic disorder in a large population-based cohort of young people.

METHODS

In this study, 79,917 new cases of allergic rhinitis between 1998 and 2012 in individuals younger than 20 years were identified from Taiwan's National Health Insurance Research Database. One control (nonallergic rhinitis) per case (allergic rhinitis) was randomly selected from the remaining sample, matching for age, sex, residence, and insurance premium. Both groups were followed until the end of 2013 for incidence of panic disorder. Cox regression analysis was performed, adjusting for sex, age, residence, insurance premium, systemic steroids, asthma, atopic dermatitis, allergic conjunctivitis, attention deficit hyperactivity disorder, depression, and Charlson index.

RESULTS

Allergic rhinitis was associated with a 2-fold increase in risk for panic disorder after adjustment for other variables. Additional independent risk factor of panic disorders were female sex, older age group, and depression.

LIMITATIONS

Lifestyle, substance use, smoking by the patient or family members, and psychosocial stressors were not evaluated.

CONCLUSIONS

Allergic rhinitis was associated with increased risk of panic disorder. Assessment and intervention of allergy rhinitis among young people with panic disorder are critical.

Panic disorders: The role of genetics and epigenetics

Panic disorder is characterized by symptoms with abrupt surges of fear with palpitations, sweating, trembling, heat sensations. Considering its disease burden on each individual and on society, understanding its etiology is important. Though no one specific etiology has been known, like other psychiatric disorders, multiple factors such as genetic, environmental, neurobiological, psychopathological factors have been suggested. In this article, we reviewed currently known etiologies and related study results, regarding especially genetic and epigenetic aspects of the panic disorder. Early studies, including twin studies, family studies, adoption studies suggested highly familial trait of panic disorder. Linkage studies, either, found panic disorder is not a single gene disorder but confirmed existence of multiple related genes. Chromosome and candidate gene studies found few related genes, NPY, ADORA2A, COMT, IKBKE. Newer method, genome-wide association studies (GWAS) have been searching for newer genes. No genome-wide significant genes, however, were detected, confirming previously known candidate genes, NPY5R on 4q31.3-32, BDKRB2 on 14q32, instead. Epigenetic modification has also been studied on many different psychiatric disorders. Monoamine oxidase A (MAOA) hypomethylation, taken together with negative life events, showed relation with panic disorder. Glutamate decarbodylases 1 (GAD1) hypomethylation was also specific on panic disorder patients. Relation with noradrenaline transporter (NET) gene SLC6a2 promoter methylation has also been studied. In conclusion, no specific gene or epigenetic pattern can fully explain etiology of panic disorder. Few genes and epigenetic patterns, however, showed strong association with panic disorder compared to healthy controls. Considering its multivariable background, further studies with larger populations can confirm current results and clarify etiologies of panic disorder.

GAD65 Promoter Polymorphism rs2236418 Modulates Harm Avoidance in Women via Inhibition/Excitation Balance in the Rostral ACC

Anxiety disorders are common and debilitating conditions with higher prevalence in women. However, factors that predispose women to anxiety phenotypes are not clarified. Here we investigated potential contribution of the single nucleotide polymorphism rs2236418 in GAD2 gene to changes in regional inhibition/excitation balance, anxiety-like traits, and related neural activity in both sexes. One hundred and five healthy individuals were examined with high-field (7T) multimodal magnetic resonance imaging (MRI); including resting-state functional MRI in combination with assessment of GABA and glutamate (Glu) levels via MR spectroscopy. Regional GABA/Glu levels in anterior cingulate cortex (ACC) subregions were assessed as mediators of gene-personality interaction for the trait harm avoidance and moderation by sex was tested. In AA homozygotes, with putatively lower GAD2 promoter activity, we observed increased intrinsic neuronal activity and higher inhibition/excitation balance in pregenual ACC (pgACC) compared with G carriers. The pgACC drove a significant interaction of genotype, region, and sex, where inhibition/excitation balance was significantly reduced only in female AA carriers. This finding was specific for rs2236418 as other investigated single nucleotide polymorphisms of the GABA synthesis related enzymes (GAD1, GAD2, and GLS) were not significant. Furthermore, only in women there was a negative association of pgACC GABA/Glu ratios with harm avoidance. A moderated-mediation model revealed that pgACC GABA/Glu also mediated the association between the genotype variant and level of harm avoidance, dependent on sex. Our data thus provide new insights into the neurochemical mechanisms that control emotional endophenotypes in humans and constitute predisposing factors for the development of anxiety disorders in women.SIGNIFICANCE STATEMENT Anxiety disorders are among the most common and burdensome psychiatric disorders, with higher prevalence rates in women. The causal mechanisms are, however, poorly understood. In this study we propose a neurobiological basis that could help to explain female bias of anxiety endophenotypes. Using magnetic resonance brain imaging and personality questionnaires we show an interaction of the genetic variation rs2236418 in the GAD2 gene and sex on GABA/glutamate (Glu) balance in the pregenual anterior cingulate cortex (pgACC), a region previously connected to affect regulation and anxiety disorders. The GAD2 gene polymorphism further influenced baseline neuronal activity in the pgACC. Importantly, GABA/Glu was shown to mediate the relationship between the genetic variant and harm avoidance, however, only in women.

A Neural "Tuning Curve" for Multisensory Experience and Cognitive-Perceptual Schizotypy

Our coherent perception of external events is enabled by the integration of inputs from different senses occurring within a range of temporal offsets known as the temporal binding window (TBW), which varies from person to person. A relatively wide TBW may increase the likelihood that stimuli originating from different environmental events are erroneously integrated and abnormally large TBW has been found in psychiatric disorders characterized by unusual perceptual experiences. Despite strong evidence of inter-individual differences in TBW, both within clinical and nonclinical populations, the neurobiological underpinnings of this variability remain unclear. We adopted an integrated strategy linking TBW to temporal dynamics in functional magnetic resonance imaging (fMRI)-resting-state activity and cortical excitation/inhibition (E/I) balance. E/I balance was indexed by glutamate/Gamma-AminoButyric Acid (GABA) concentrations and common variation in glutamate and GABA genes in a healthy sample. Stronger resting-state long-range temporal correlations, indicated by larger power law exponent (PLE), in the auditory cortex, robustly predicted narrower audio-tactile TBW, which was in turn associated with lower cognitive-perceptual schizotypy. Furthermore, PLE was highest and TBW narrowest for individuals with intermediate levels of E/I balance, with shifts towards either extreme resulting in reduced multisensory temporal precision and increased schizotypy, effectively forming a neural "tuning curve" for multisensory experience and schizophrenia risk. Our findings shed light on the neurobiological underpinnings of multisensory integration and its potentially clinically relevant inter-individual variability.

Candidate genes in panic disorder: meta-analyses of 23 common variants in major anxiogenic pathways

The utilization of molecular genetics approaches in examination of panic disorder (PD) has implicated several variants as potential susceptibility factors for panicogenesis. However, the identification of robust PD susceptibility genes has been complicated by phenotypic diversity, underpowered association studies and ancestry-specific effects. In the present study, we performed a succinct review of case-control association studies published prior to April 2015. Meta-analyses were performed for candidate gene variants examined in at least three studies using the Cochrane Mantel-Haenszel fixed-effect model. Secondary analyses were also performed to assess the influences of sex, agoraphobia co-morbidity and ancestry-specific effects on panicogenesis. Meta-analyses were performed on 23 variants in 20 PD candidate genes. Significant associations after correction for multiple testing were observed for three variants, TMEM132D rs7370927 (T allele: odds ratio (OR)=1.27, 95% confidence interval (CI): 1.15-1.40, P=2.49 × 10(-6)), rs11060369 (CC genotype: OR=0.65, 95% CI: 0.53-0.79, P=1.81 × 10(-5)) and COMT rs4680 (Val (G) allele: OR=1.27, 95% CI: 1.14-1.42, P=2.49 × 10(-5)) in studies with samples of European ancestry. Nominal associations that did not survive correction for multiple testing were observed for NPSR1 rs324891 (T allele: OR=1.22, 95% CI: 1.07-1.38, P=0.002), TPH1 rs1800532 (AA genotype: OR=1.46, 95% CI: 1.14-1.89, P=0.003) and HTR2A rs6313 (T allele: OR=1.19, 95% CI: 1.07-1.33, P=0.002) in studies with samples of European ancestry and for MAOA-uVNTR in female PD (low-active alleles: OR=1.21, 95% CI: 1.07-1.38, P=0.004). No significant associations were observed in the secondary analyses considering sex, agoraphobia co-morbidity and studies with samples of Asian ancestry. Although these findings highlight a few associations, PD likely involves genetic variation in a multitude of biological pathways that is diverse among populations. Future studies must incorporate larger sample sizes and genome-wide approaches to further quantify the observed genetic variation among populations and subphenotypes of PD.

The GAD65 knock out mouse - a model for GABAergic processes in fear- and stress-induced psychopathology

The γ-amino butyric acid (GABA) synthetic enzyme glutamic acid decarboxylase (GAD)65 is critically involved in the activity-dependent regulation of GABAergic inhibition in the central nervous system. It is also required for the maturation of the GABAergic system during adolescence, a phase that is critical for the development of several neuropsychiatric diseases. Mice bearing a null mutation of the GAD65 gene develop hyperexcitability of the amygdala and hippocampus, and a phenotype of increased anxiety and pathological fear memory reminiscent of posttraumatic stress disorder. Although genetic association of GAD65 in human has not yet been reported, these findings are in line with observations of reduced GABAergic function in these brain regions of anxiety disorder patients. The particular value of GAD65(-/-) mice thus lies in modeling the effects of reduced GABAergic function in the mature nervous system. The expression of GAD65 and a second GAD isozyme, GAD67, are differentially regulated in response to stress in limbic brain areas suggesting that by controlling GABAergic inhibition these enzymes determine the vulnerability for the development of pathological anxiety and other stress-induced phenotypes. In fact, we could recently show that GAD65 haplodeficiency, which results in delayed postnatal increase of GABA levels, provides resilience to juvenile-stress-induced anxiety to GAD65(+/-) mice thus foiling the increased fear and anxiety in homozygous GAD65(-/-) mice.

MicroRNA hsa-miR-4717-5p regulates RGS2 and may be a risk factor for anxiety-related traits

Regulator of G-protein Signaling 2 (RGS2) is a key regulator of G-protein-coupled signaling pathways involved in fear and anxiety. Data from rodent models and genetic analysis of anxiety-related traits and disorders in humans suggest down-regulation of RGS2 expression to be a risk factor for anxiety. Here we investigated, whether genetic variation in microRNAs mediating posttranscriptional down-regulation of RGS2 may be a risk factor for anxiety as well. 75 microRNAs predicted to regulate RGS2 were identified by four bioinformatic algorithms and validated experimentally by luciferase reporter gene assays. Specificity was confirmed for six microRNAs (hsa-miR-1271-5p, hsa-miR-22-3p, hsa-miR-3591-3p, hsa-miR-377-3p, hsa-miR-4717-5p, hsa-miR-96-5p) by disrupting their seed sequence at the 3' untranslated region of RGS2. Hsa-miR-4717-5p showed the most robust effect on RGS2 and regulated two other candidate genes of anxiety disorders (CNR1 and IKBKE) as well. Two SNPs (rs150925, rs161427) within and 1,000 bp upstream of the hostgene of hsa-miR-4717-5p (MIR4717) show a minor allele frequency greater than 0.05. Both were in high linkage disequilibrium (r(2) = 1, D' = 1) and both major (G) alleles showed a trend for association with panic disorder with comorbid agoraphobia in one of two patient/control samples (combined n(patients) = 497). Dimensional anxiety traits, as described by Anxiety Sensitivity Index (ASI) and Agoraphobic Cognitions Questionnaire (ACQ) were significantly higher among carriers of both major (G) alleles in a combined patient/control sample (n(combined) = 831). Taken together, data indicate that MIR4717 regulates human RGS2 and contributes to the genetic risk towards anxiety-related traits.

Validation of candidate anxiety disorder genes using a carbon dioxide challenge task

Few replicable genetic variants have been identified in the etiology of heritable anxiety disorders such as panic disorder. Endophenotypic measures that have reduced heterogeneity may provide more powerful targets for gene identification. We assessed hypersensitivity to carbon dioxide (a reliable endophenotype of panic and anxiety) in 174 Caucasian college students, who were genotyped on 26 polymorphic markers from 11 genes previously associated with panic/anxiety. Individual trajectories of respiratory and subjective anxiety response to carbon dioxide were measured and tested for association with these genetic markers. One marker in the acid-sensing ion channel 1 (ASIC1) gene, rs1108923, had a significant association with respiratory rate. No genes had a significant association with subjective anxiety response. Our findings support previously reported associations between ASIC1 and panic/anxiety, but not other genes previously associated with anxiety disorders. The use of endophenotypic markers is a promising avenue for gene identification in anxiety and other complex disorders.

Transcriptional regulation of glutamic acid decarboxylase in the male mouse amygdala by dietary phyto-oestrogens

Phyto-oestrogens are biologically active components of many human and laboratory animal diets. In the present study, we investigated, in adult male mice with C57BL/6 genetic background, the effects of a reduced phyto-oestrogens intake on anxiety-related behaviour and associated gene expression in the amygdala. After 6 weeks on a low-phyto-oestrogen diet (< 20 μg/g cumulative phyto-oestrogen content), animals showed reduced centre exploration in an open-field task compared to their littermates on a soybean-based standard diet (300 μg/g). Freezing behaviour in an auditory fear memory task, in contrast, was not affected. We hypothesised that this mildly increased anxiety may involve changes in the function of GABAergic local circuit neurones in the amygdala. Using GAD67(+/GFP) mice, we could demonstrate reduced transcription of the GAD67 gene in the lateral and basolateral amygdala under the low-phyto-oestrogen diet. Analysis of mRNA levels in microdissected samples confirmed this regulation and demonstrated concomitant changes in expression of the second glutamic acid decarboxylase (GAD) isoform, GAD65, as well as the anxiolytic neuropeptide Y. These molecular and behavioural alterations occurred without apparent changes in circulating oestrogens or testosterone levels. Our data suggest that expression regulation of interneurone-specific gene products in the amygdala may provide a mechanism for the control of anxiety-related behaviour through dietary phyto-oestrogens.

Gender-specific association between the COMT Val158Met polymorphism and openness to experience in panic disorder patients

BACKGROUND

Because major depression and panic disorder are both more prevalent among females and since several lines of evidence suggest that genetic factors might influence an individual's vulnerability to panic disorder, gene-gender interactions are being examined in such psychiatric disorders and mental traits. A number of studies have suggested that specific genes, e.g. catechol-O-methyltransferase (COMT), might lead to distinct clinical characteristics of panic disorder.

METHOD

We compared gender-specific personality-related psychological factors of 470 individuals with panic disorder and 458 healthy controls in terms of their COMT Val158Met polymorphism and their scores on the Revised NEO Personality Inventory (NEO PI-R) and State-Trait Anxiety Inventory (STAI) with a 1-way analysis of covariance.

RESULTS

In the male panic disorder patients, the NEO PI-R score for openness to experience was significantly lower in the Met/Met carrier group, whereas there was no such association among the female panic disorder patients or the male or female control groups.

CONCLUSION

The gender-specific effect of the COMT genotype suggests that the COMT Val/Met genotype may influence a personality trait, openness to experience, in males with panic disorder.

Molecular signatures of mood stabilisers highlight the role of the transcription factor REST/NRSF

BACKGROUND

The purpose of this study was to address the affects of mood modifying drugs on the transcriptome, in a tissue culture model, using qPCR arrays as a cost effective approach to identifying regulatory networks and pathways that might coordinate the cell response to a specific drug.

METHODS

We addressed the gene expression profile of 90 plus genes associated with human mood disorders using the StellARray™ qPCR gene expression system in the human derived SH-SY5Y neuroblastoma cell line.

RESULTS

Global Pattern Recognition (GPR) analysis identified a total of 9 genes (DRD3(⁎), FOS(†), JUN(⁎), GAD1(⁎†), NRG1(⁎), PAFAH1B3(⁎), PER3(⁎), RELN(⁎) and RGS4(⁎)) to be significantly regulated in response to cellular challenge with the mood stabilisers sodium valproate ((⁎)) and lithium ((†)). Modulation of FOS and JUN highlights the importance of the activator protein 1 (AP-1) transcription factor pathway in the cell response. Enrichment analysis of transcriptional networks relating to this gene set also identified the transcription factor neuron restrictive silencing factor (NRSF) and the oestrogen receptor as an important regulatory mechanism.

LIMITATIONS

Cell line models offer a window of what might happen in vivo but have the benefit of being human derived and homogenous with regard to cell type.

CONCLUSIONS

This data highlights transcription factor pathways, acting synergistically or separately, in the modulation of specific neuronal gene networks in response to mood stabilising drugs. This model can be utilised in the comparison of the action of multiple drug regimes or for initial screening purposes to inform optimal drug design.

SPOCK3, a risk gene for adult ADHD and personality disorders

Attention-deficit/hyperactivity disorder (ADHD) is the most frequent psychiatric disorder in children, where it displays a global prevalence of 5 %. In up to 50 % of the cases, ADHD may persist into adulthood (aADHD), where it is often comorbid with personality disorders. Due to a potentially heritable nature of this comorbidity, we hypothesized that their genetic framework may contain common risk-modifying genes. SPOCK3, a poorly characterized, putatively Ca(2+)-binding extracellular heparan/chondroitin sulfate proteoglycan gene encoded by the human chromosomal region 4q32.3, was found to be associated with polymorphisms among the top ranks in a genome-wide association study (GWAS) on ADHD and a pooled GWAS on personality disorder (PD). We therefore genotyped 48 single nucleotide polymorphisms (SNPs) representative of the SPOCK3 gene region in 1,790 individuals (n aADHD = 624, n PD = 630, n controls = 536). In this analysis, we found two SNPs to be nominally associated with aADHD (rs7689440, rs897511) and four PD-associated SNPs (rs7689440, rs897511, rs17052671 and rs1485318); the latter even reached marginal significance after rigorous Bonferroni correction. Bioinformatics tools predicted a possible influence of rs1485318 on transcription factor binding, whereas the other candidate SNPs may have effects on alternative splicing. Our results suggest that SPOCK3 may modify the genetic risk for ADHD and PD; further studies are, however, needed to identify the underlying mechanisms.

Epigenetic signature of panic disorder: a role of glutamate decarboxylase 1 (GAD1) DNA hypomethylation?

Glutamate decarboxylases (GAD67/65; GAD1/GAD2) are crucially involved in gamma-aminobutyric acid (GABA) synthesis and thus were repeatedly suggested to play an important role in the pathogenesis of anxiety disorders. In the present study, DNA methylation patterns in the GAD1 and GAD2 promoter and GAD1 intron 2 regions were investigated for association with panic disorder, with particular attention to possible effects of environmental factors. Sixty-five patients with panic disorder (f=44, m=21) and 65 matched healthy controls were analyzed for DNA methylation status at 38 GAD1 promoter/intron2 and 10 GAD2 promoter CpG sites via direct sequencing of sodium bisulfate treated DNA extracted from blood cells. Recent positive and negative life events were ascertained. Patients and controls were genotyped for GAD1 rs3762556, rs3791878 and rs3762555, all of which are located in the analyzed promoter region. Patients with panic disorder exhibited significantly lower average GAD1 methylation than healthy controls (p<0.001), particularly at three CpG sites in the promoter as well as in intron 2. The occurrence of negative life events was correlated with relatively decreased average methylation mainly in the female subsample (p=0.01). GAD1 SNP rs3762555 conferred a significantly lower methylation at three GAD1 intron 2 CpG sites (p<0.001). No differential methylation was observed in the GAD2 gene. The present pilot data suggest a potentially compensatory role of GAD1 gene hypomethylation in panic disorder possibly mediating the influence of negative life events and depending on genetic variation. Future studies are warranted to replicate the present finding in independent samples, preferably in a longitudinal design.