Genetics of posttraumatic stress disorder

Disentangling sex differences in the shared genetic architecture of posttraumatic stress disorder, traumatic experiences, and social support with body size and composition

There is a well-known association of traumatic experiences and posttraumatic stress disorder (PTSD) with body size and composition, including consistent differences between sexes. However, the biology underlying these associations is unclear. To understand the genetic underpinnings of this complex relationship, we investigated genome-wide datasets informative of African and European ancestries from the Psychiatric Genomic Consortium, the UK Biobank, the GIANT Consortium, and the Million Veteran Program. We used genome-wide association statistics to estimate sex-specific genetic correlations (r g ) of traumatic experiences, social support, and PTSD with multiple anthropometric traits. After multiple testing corrections (false discovery rate, FDR q < 0.05), we observed 58 significant r g relationships in females (e.g., childhood physical abuse and body mass index, BMI r g  = 0.245, p = 3.88 × 10-10) and 21 significant r g relationships in males (e.g., been involved in combat or exposed to warzone and leg fat percentage; r g  = 0.405, p = 4.42 × 10-10). We performed causal inference analyses of these genetic overlaps using Mendelian randomization and latent causal variable approaches. Multiple female-specific putative causal relationships were observed linking body composition/size with PTSD (e.g., leg fat percentage→PTSD; beta = 0.319, p = 3.13 × 10-9), traumatic experiences (e.g., childhood physical abuse→waist circumference; beta = 0.055, p = 5.07 × 10-4), and childhood neglect (e.g., "someone to take you to doctor when needed as a child"→BMI; beta = -0.594, p = 1.09 × 10-5). In males, we observed putative causal effects linking anthropometric-trait genetic liabilities to traumatic experiences (e.g., BMI→childhood physical abuse; beta = 0.028, p = 8.19 × 10-3). Some of these findings were replicated in individuals of African descent although the limited sample size available did not permit us to conduct a sex-stratified analysis in this ancestry group. In conclusion, our findings provide insights regarding sex-specific causal networks linking anthropometric traits to PTSD, traumatic experiences, and social support.

Single-nucleotide polymorphisms in genes related to the hypothalamic-pituitary-adrenal axis as risk factors for posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is a common psychiatric disorder. The etiology of PTSD is multifactorial, depending on many environmental and genetic risk factors, and the exposure to life or physical integrity-threatening events. Several studies have shown significant correlations of many neurobiological findings with PTSD. Hypothalamic-pituitary-adrenal (HPA) axis dysfunction is strongly correlated with this disorder. One hypothesis is that HPA axis dysfunction may precede the traumatic event, suggesting that genes expressed in the HPA axis may be involved in the development of PTSD. This article reviews molecular genetic studies related to PTSD collected through a literature search performed in PubMed, MEDLINE, ScienceDirect, and Scientific Electronic Library Online (SciELO). The results of these studies suggest that several polymorphisms in the HPA axis genes, including FKBP5, NR3C1, CRHR1, and CRHR2, may be risk factors for PTSD development or may be associated with the severity of PTSD symptoms.

The impact of healthy parenting as a protective factor for posttraumatic stress disorder in adulthood: a case-control study

BACKGROUND

Early life social adversity can influence stress response mechanisms and is associated with anxious behaviour and reductions in callosal area later in life.

OBJECTIVE

To evaluate the association between perceptions of parental bonding in childhood/adolescence, hypothalamic-pituitary-adrenal (HPA) axis response, and callosal structural integrity in adult victims of severe urban violence with and without PTSD.

METHODS

Seventy-one individuals with PTSD and 62 without the disorder were assessed with the Parental Bonding Instrument (PBI). The prednisolone suppression test was administered to assess cortisol levels, and magnetic resonance imaging was used to assess the total area of the corpus callosum (CC), as well as the areas of callosal subregions.

RESULTS

The PBI items related to the perception of 'not having a controlling mother' (OR 4.84; 95%CI [2.26-10.3]; p=0.01), 'having a caring father' (OR 2.46; 95'%CI [1.18-5.12]; p=0.02), and 'not having controlling parents' (OR 2.70; 95%CI [1.10-6.63]; p=0.04) were associated with a lower risk of PTSD. The PTSD group showed a blunted response to the prednisolone suppression test, with lower salivary cortisol levels upon waking up (p=0.03). Individuals with PTSD had smaller total CC area than those without the disorder, but these differences were not statistically significant (e-value =0.34).

CONCLUSIONS

Healthy parental bonding, characterized by the perception of low parental control and high affection, were associated with a lower risk of PTSD in adulthood, suggesting that emotional enrichment and the encouragement of autonomy are protective against PTSD in adulthood.

A review on the evidence of transgenerational transmission of posttraumatic stress disorder vulnerability

OBJECTIVE

To understand the risks of posttraumatic stress disorder (PTSD) development in the next generation of PTSD patients, we conducted a review on the biological, but not genetic, evidence of transgenerational transmission of PTSD vulnerability.

METHODS

Pertinent articles published from 1985 to September 2011 were searched using online academic search engines, including MEDLINE, EMBASE, ScienceDirect, OVID, PsycLIT, and SCOPUS, and a non-systematic review was conducted.

RESULTS

There is paradoxical evidence that hypothalamic-pituitary-adrenal axis changes in PTSD patients may also be evident in their offspring. This effect and biological vulnerability to PTSD may be transmitted across generations through maternal epigenetic programming during pregnancy. The samples of most studies, which were not large enough and represented the outcome of few research groups, consisted of a specific type of patients with a particular trauma.

CONCLUSIONS

There is still a need to conduct studies in other geographical areas with different genetic background and larger samples considering different types of trauma other than those specified in the current literature, so as to strengthen the evidence of transgenerational transmission of PTSD vulnerability.

Considering trauma exposure in the context of genetics studies of posttraumatic stress disorder: a systematic review

BACKGROUND

Posttraumatic stress disorder (PTSD) is a debilitating anxiety disorder. Surveys of the general population suggest that while 50-85% of Americans will experience a traumatic event in their lifetime, only 2-50% will develop PTSD. Why some individuals develop PTSD following trauma exposure while others remain resilient is a central question in the field of trauma research. For more than half a century, the role of genetic influences on PTSD has been considered as a potential vulnerability factor. However, despite the exponential growth of molecular genetic studies over the past decade, limited progress has been made in identifying true genetic variants for PTSD.

METHODS

In an attempt to aid future genome wide association studies (GWAS), this paper presents a systematic review of 28 genetic association studies of PTSD. Inclusion criteria required that 1) all participants were exposed to Criterion A traumatic events, 2) polymorphisms of relevant genes were genotyped and assessed in relation to participants' PTSD status, 3) quantitative methods were used, and 4) articles were published in English and in peer-reviewed journals. In the examination of these 28 studies, particular attention was given to variables related to trauma exposure (e.g. number of traumas, type of trauma).

RESULTS

Results indicated that most articles did not report on the GxE interaction in the context of PTSD or present data on the main effects of E despite having data available. Furthermore, some studies that did consider the GxE interaction had significant findings, underscoring the importance of examining how genotypes can modify the effect of trauma on PTSD. Additionally, results indicated that only a small number of genes continue to be studied and that there were marked differences in methodologies across studies, which subsequently limited robust conclusions.

CONCLUSIONS

As trauma exposure is a necessary condition for the PTSD diagnosis, this paper identifies gaps in the current literature as well as provides recommendations for how future GWAS studies can most effectively incorporate trauma exposure data in both the design and analysis phases of studies.

Prevention of stress-impaired fear extinction through neuropeptide s action in the lateral amygdala

Stressful and traumatic events can create aversive memories, which are a predisposing factor for anxiety disorders. The amygdala is critical for transforming such stressful events into anxiety, and the recently discovered neuropeptide S transmitter system represents a promising candidate apt to control these interactions. Here we test the hypothesis that neuropeptide S can regulate stress-induced hyperexcitability in the amygdala, and thereby can interact with stress-induced alterations of fear memory. Mice underwent acute immobilization stress (IS), and neuropeptide S and a receptor antagonist were locally injected into the lateral amygdala (LA) during stress exposure. Ten days later, anxiety-like behavior, fear acquisition, fear memory retrieval, and extinction were tested. Furthermore, patch-clamp recordings were performed in amygdala slices prepared ex vivo to identify synaptic substrates of stress-induced alterations in fear responsiveness. (1) IS increased anxiety-like behavior, and enhanced conditioned fear responses during extinction 10 days after stress, (2) neuropeptide S in the amygdala prevented, while an antagonist aggravated, these stress-induced changes of aversive behaviors, (3) excitatory synaptic activity in LA projection neurons was increased on fear conditioning and returned to pre-conditioning values on fear extinction, and (4) stress resulted in sustained high levels of excitatory synaptic activity during fear extinction, whereas neuropeptide S supported the return of synaptic activity during fear extinction to levels typical of non-stressed animals. Together these results suggest that the neuropeptide S system is capable of interfering with mechanisms in the amygdala that transform stressful events into anxiety and impaired fear extinction.

Behavioral genetics of affective and anxiety disorders

As shown by clinical genetic studies, affective and anxiety disorders are complex genetic disorders with genetic and environmental factors interactively determining their respective pathomechanism. Advances in molecular genetic techniques including linkage studies, association studies, and genome-wide association studies allow for the detailed dissection of the genetic influence on the development of these disorders. Besides the molecular genetic investigation of categorical entities according to standardized diagnostic criteria, intermediate phenotypes comprising neurobiological or neuropsychological traits (e.g., neuronal correlates of emotional processing) that are linked to the disease of interest and that are heritable, have been proposed to be closer to the underlying genotype than the overall disease phenotype. These intermediate phenotypes are dimensional and more precisely defined than the categorical disease phenotype, and therefore have attracted much interest in the genetic investigation of affective and anxiety disorders. Given the complex genetic nature of affective and anxiety disorders with an interaction of multiple risk genes and environmental influences, the interplay of genetic factors with environmental factors is investigated by means of gene-environment interaction (GxE) studies. Pharmacogenetic studies aid in the dissection of the genetically influenced heterogeneity of psychotropic drug response and may contribute to the development of a more individualized treatment of affective and anxiety disorders. Finally, there is some evidence for genetic factors potentially shared between affective and anxiety disorders pointing to a possible overlapping phenotype between anxiety disorders and depression.

Using polymorphisms in FKBP5 to define biologically distinct subtypes of posttraumatic stress disorder: evidence from endocrine and gene expression studies

CONTEXT

Polymorphisms in the gene encoding the glucocorticoid receptor (GR) regulating co-chaperone FKBP5 have been shown to alter GR sensitivity and are associated with an increased risk to develop posttraumatic stress disorder (PTSD).

OBJECTIVE

To investigate interactions of the FKBP5 single-nucleotide polymorphism rs9296158 and PTSD symptoms on baseline cortisol level, low-dose dexamethasone suppression, and whole-blood gene expression.

DESIGN

Association of FKBP5 genotypes and PTSD symptoms with endocrine measures and genome-wide expression profiles.

SETTING

Waiting rooms of general medical and gynecological clinics of an urban hospital at Emory University.

PARTICIPANTS

The 211 participants were primarily African American (90.05%) and of low socioeconomic status and had high rates of trauma and PTSD.

MAIN OUTCOME MEASURES

Baseline and post-dexamethasone suppression cortisol measures and gene expression levels.

RESULTS

In our endocrine study, we found that only risk allele A carriers of rs9296158 showed GR supersensitivity with PTSD; in contrast, baseline cortisol levels were decreased in PTSD only in patients with the GG genotype. Expression of 183 transcripts was significantly correlated with PTSD symptoms after multiple testing corrections. When adding FKBP5 genotype and its interaction with PTSD symptoms, expression levels of an additional 32 genes were significantly regulated by the interaction term. Within these 32 genes, previously reported PTSD candidates were identified, including FKBP5 and the IL18 and STAT pathways. Significant overrepresentation of steroid hormone transcription factor binding sites within these 32 transcripts was observed, highlighting the fact that the earlier-described genotype and PTSD-dependent differences in GR sensitivity could drive the observed gene expression pattern. Results were validated by reverse transcriptase-polymerase chain reaction and replicated in an independent sample (N = 98).

CONCLUSIONS

These data suggest that the inheritance of GR sensitivity-moderating FKBP5 polymorphisms can determine specific types of hypothalamic-pituitary-adrenal axis dysfunction within PTSD, which are also reflected in gene-expression changes of a subset of GR-responsive genes. Thus, these findings indicate that functional variants in FKBP5 are associated with biologically distinct subtypes of PTSD.

Gene × environment vulnerability factors for PTSD: the HPA-axis

Post-traumatic stress disorder (PTSD) is a severely debilitating psychiatric condition. Although a lifetime trauma incidence of 40-90% has been reported in the general population, the overall lifetime prevalence for PTSD ranges between 7-12%, suggesting individual-specific differences towards the susceptibility to PTSD. While studies investigating main genetic effects associated with PTSD have yielded inconsistent findings, there is growing evidence supporting the role of gene-environment (G × E) interactions in PTSD. The hypothalamus pituitary adrenal (HPA) axis is one of the main systems activated after exposure to a trauma and perturbations in this system are one of the more consistent neurobiological abnormalities observed in PTSD. Genes regulating the HPA-axis are therefore interesting candidates for G × E studies in PTSD. This article will review the concept and initial results of G × E interactions with polymorphisms in these genes for PTSD. In addition, the use of alternate phenotypes and more complex interaction models such as G × G × E or G × E × E will be explored. Finally, putative molecular mechanisms for these interactions will be presented. The research presented in this article indicates that a combined analysis of environmental, genetic, endophenotype and epigenetic data will be necessary to better understand pathomechanisms in PTSD. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

The neurobiology of anxiety disorders: brain imaging, genetics, and psychoneuroendocrinology

Anxiety disorders are highly comorbid with each other and with major depressive disorder. As syndromes, anxiety and mood disorders share many symptoms, and several treatments are effective for both. Despite this overlap, there exist many distinguishing features that support the continued classification of individual anxiety disorders that are distinct from each other and from major depression. The goal of this article is to describe the key biological similarities and differences between anxiety disorders.

Psychogenetics of post-traumatic stress disorder: a short review

Post-traumatic stress disorder is a commonly overlooked psychiatric disorder due to the heterogeneity of symptoms that may simulate many other psychiatric disorders. Such heterogeneity of manifestations may be explained by the multifaceted nature of the different neurotransmitters, endocrinologic axis, and their genetic basis, that are implicated in the etiology. Although this disorder has been studied from many different perspectives, its etiology is still enigmatic. This minireview demonstrates, in brief, that different susceptibility genes are associated with post traumatic stress disorder.

Putative biological mechanisms for the association between early life adversity and the subsequent development of PTSD

RATIONALE

Early Life Stress (ELS) increases risk for both adult traumatization and posttraumatic stress disorder (PTSD). Adult PTSD may also reflect a continuation of a response to an earlier exposure to adversity. Given similarities between neuroendocrine aspects of PTSD and ELS, such as in reduced cortisol signaling and glucocorticoid receptor (GR) responsiveness, some aspects of the biology of PTSD may reflect biological correlates of risk.

OBJECTIVES

This paper will examine how empirical findings regarding the biological basis of ELS can inform our understanding of the neuroendocrinology of PTSD. This paper will also propose a hypothetical model to guide future research that integrates genetic, epigenetic, neuroendocrine, and psychological observations to understand the contribution of ELS neurobiology to PTSD.

RESULTS

Recent genetic findings demonstrate heritable aspects of at least some of these cortisol-related disturbances. Furthermore, ELS may produce at least some of the PTSD-associated changes in glucocorticoid responsiveness through epigenetic mechanisms such as developmental programming. These, then, may contribute to enduring changes in stress responsiveness as well as enhanced risk for adult exposure and PTSD.

CONCLUSION

Molecular mechanisms associated with gene x environment interactions or GR programming are essential in explaining current observations in the neuroendocrinology of PTSD that have been difficult to understand through the lens of contemporary stress theory.

The risk of posttraumatic stress disorder after trauma depends on traumatic load and the catechol-o-methyltransferase Val(158)Met polymorphism

BACKGROUND

The risk for posttraumatic stress disorder (PTSD) depends on the number of traumatic event types experienced in a dose-response relationship, but genetic factors are known to also influence the risk of PTSD. The catechol-O-methyltransferase (COMT) Val158Met polymorphism has been found to affect fear extinction and might play a role in the etiology of anxiety disorders.

METHODS

Traumatic load and lifetime and current diagnosis of PTSD and COMT genotype were assessed in a sample of 424 survivors of the Rwandan Genocide living in the Nakivale refugee camp in southwestern Uganda.

RESULTS

Higher numbers of different lifetime traumatic event types led to a higher prevalence of lifetime PTSD in a dose-response relationship. However, this effect was modulated by the COMT genotype: whereas Val allele carriers showed the typical dose-response relationship, Met/Met homozygotes exhibited a high risk for PTSD independently of the severity of traumatic load.

CONCLUSIONS

The present findings indicate a gene-environment interaction between the human COMT Val158Met polymorphism and the number of traumatic event types experienced in the risk of developing PTSD.

Neuroendocrinology of post-traumatic stress disorder

Dysregulation of the stress system, including the hypothalamic-pituitary-adrenal (HPA) axis and the locus caeruleus/norepinephrine-sympathetic nervous system (SNS), is involved in the pathophysiology of post-traumatic stress disorder (PTSD), an anxiety disorder that develops after exposure to traumatic life events. Neuroendocrine studies in individuals with PTSD have demonstrated elevated basal cerebrospinal fluid corticotropin-releasing hormone concentrations and contradictory results from peripheral measurements, exhibiting low 24 hours excretion of urinary free cortisol, low or normal circulating cortisol levels or even high plasma cortisol levels. The direction of HPA axis activity (hyper-/or hypo-activation), as evidenced by peripheral cortisol measures, may depend on variables such as genetic vulnerability and epigenetic changes, age and developmental stage of the individual, type and chronicity of trauma, co-morbid depression or other psychopathology, alcohol or other drug abuse and time since the traumatic experience. On the other hand, peripheral biomarkers of the SNS activity are more consistent, showing increased 24h urinary or plasma catecholamines in PTSD patients compared to control individuals. Chronically disturbed hormones in PTSD may contribute to brain changes and further emotional and behavior symptoms and disorders, as well as to an increased cardiometabolic risk.

Status of glucocorticoid alterations in post-traumatic stress disorder

The current status of glucocorticoid alterations in post-traumatic stress disorder (PTSD) will be described in this chapter. Emphasis will be placed on data that suggest that at least some glucocorticoid-related observations in PTSD reflect pretraumatic glucocorticoid status. Recent observations have provided some evidence that pretraumatic glucocorticoid alterations may arise from genetic, epigenetic, and possibly other environmental influences that serve to increase the likelihood of developing PTSD following trauma exposure, as well as modulate attendant biological alterations associated with its pathophysiology. Current studies in the field of PTSD employ glucocorticoid challenge strategies to delineate effects of exogenously administered glucocorticoids on neuroendocrine, cognitive, and brain function. Results of these studies have provided an important rationale for using glucocorticoid strategies in the treatment of PTSD.

The neurobiology of anxiety disorders: brain imaging, genetics, and psychoneuroendocrinology

Anxiety disorders are highly comorbid with each other and with major depressive disorder. As syndromes, anxiety and mood disorders share many symptoms, and several treatments are effective for both. Despite this overlap, there exist many distinguishing features that support the continued classification of individual anxiety disorders that are distinct from each other and from major depression. The goal of this article is to describe the key biological similarities and differences between anxiety disorders.

Genetics of anxiety and trauma-related disorders

Anxiety disorders are the most common psychiatric illnesses in the United States with approximately 30% of the population experiencing anxiety-related symptoms in their lifetime [Kessler RC, Berglund P, Demler O, Jin R, Merikangas KR, Walters EE (2005) Lifetime prevalence and age-of-onset distributions of Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) disorders in the National Comorbidity Survey Replication. Arch Gen Psychiatry 62:593-60]. Notably, a variety of studies have demonstrated that 30-40% of the variance contributing to these disorders is heritable. In the present review, we discuss the latest findings regarding the genetic and environmental influences on the development and symptomatology of anxiety disorders. Specific emphasis is placed on posttraumatic stress disorder (PTSD) due to its uniqueness as an anxiety disorder; its diagnosis is dependent on a precipitating traumatic event and its development appears to be mediated by both genetic and environmental contributions. The co-morbidity of anxiety disorders and the potential re-classification of anxiety disorders as part of DSM-V are reviewed given the potential impact on the interpretation and design of genetic investigations. Lastly, several keys to future genetic studies are highlighted. Thorough analyses of the gene by environment (GxE) interactions that govern one's vulnerability to anxiety disorder(s), the effectiveness of individual treatment strategies, and the severity of symptoms may lead to more effective prophylactic (e.g. social support) and treatment strategies.

Protocol for investigating genetic determinants of posttraumatic stress disorder in women from the Nurses' Health Study II

BACKGROUND

One in nine American women will meet criteria for the diagnosis of posttraumatic stress disorder (PTSD) in their lifetime. Although twin studies suggest genetic influences account for substantial variance in PTSD risk, little progress has been made in identifying variants in specific genes that influence liability to this common, debilitating disorder.

METHODS AND DESIGN

We are using the unique resource of the Nurses Health Study II, a prospective epidemiologic cohort of 68,518 women, to conduct what promises to be the largest candidate gene association study of PTSD to date. The entire cohort will be screened for trauma exposure and PTSD; 3,000 women will be selected for PTSD diagnostic interviews based on the screening data. Our nested case-control study will genotype 1000 women who developed PTSD following a history of trauma exposure; 1000 controls will be selected from women who experienced similar traumas but did not develop PTSD.The primary aim of this study is to detect genetic variants that predict the development of PTSD following trauma. We posit inherited vulnerability to PTSD is mediated by genetic variation in three specific neurobiological systems whose alterations are implicated in PTSD etiology: the hypothalamic-pituitary-adrenal axis, the locus coeruleus/noradrenergic system, and the limbic-frontal neuro-circuitry of fear. The secondary, exploratory aim of this study is to dissect genetic influences on PTSD in the broader genetic and environmental context for the candidate genes that show significant association with PTSD in detection analyses. This will involve: conducting conditional tests to identify the causal genetic variant among multiple correlated signals; testing whether the effect of PTSD genetic risk variants is moderated by age of first trauma, trauma type, and trauma severity; and exploring gene-gene interactions using a novel gene-based statistical approach.

DISCUSSION

Identification of liability genes for PTSD would represent a major advance in understanding the pathophysiology of the disorder. Such understanding could advance the development of new pharmacological agents for PTSD treatment and prevention. Moreover, the addition of PTSD assessment data will make the NHSII cohort an unparalleled resource for future genetic studies of PTSD as well as provide the unique opportunity for the prospective examination of PTSD-disease associations.

Genetics of post-traumatic stress disorder: informing clinical conceptualizations and promoting future research

The purpose of this article is to provide an overview of genetic research involving post-traumatic stress disorder (PTSD). First, we summarize evidence for genetic influences on PTSD from family investigations. Second, we discuss the distinct contributions to our understanding of the genetics of PTSD permitted by twin studies. Finally, we summarize findings from molecular genetic studies, which have the potential to inform our understanding of underlying biological mechanisms for the development of PTSD.

Association of FKBP5 polymorphisms and childhood abuse with risk of posttraumatic stress disorder symptoms in adults

CONTEXT

In addition to trauma exposure, other factors contribute to risk for development of posttraumatic stress disorder (PTSD) in adulthood. Both genetic and environmental factors are contributory, with child abuse providing significant risk liability.

OBJECTIVE

To increase understanding of genetic and environmental risk factors as well as their interaction in the development of PTSD by gene x environment interactions of child abuse, level of non-child abuse trauma exposure, and genetic polymorphisms at the stress-related gene FKBP5.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional study examining genetic and psychological risk factors in 900 nonpsychiatric clinic patients (762 included for all genotype studies) with significant levels of childhood abuse as well as non-child abuse trauma using a verbally presented survey combined with single-nucleotide polymorphism (SNP) genotyping. Participants were primarily urban, low-income, black (>95%) men and women seeking care in the general medical care and obstetrics-gynecology clinics of an urban public hospital in Atlanta, Georgia, between 2005 and 2007.

MAIN OUTCOME MEASURES

Severity of adult PTSD symptomatology, measured with the modified PTSD Symptom Scale, non-child abuse (primarily adult) trauma exposure and child abuse measured using the traumatic events inventory and 8 SNPs spanning the FKBP5 locus.

RESULTS

Level of child abuse and non-child abuse trauma each separately predicted level of adult PTSD symptomatology (mean [SD], PTSD Symptom Scale for no child abuse, 8.03 [10.48] vs > or =2 types of abuse, 20.93 [14.32]; and for no non-child abuse trauma, 3.58 [6.27] vs > or =4 types, 16.74 [12.90]; P < .001). Although FKBP5 SNPs did not directly predict PTSD symptom outcome or interact with level of non-child abuse trauma to predict PTSD symptom severity, 4 SNPs in the FKBP5 locus significantly interacted (rs9296158, rs3800373, rs1360780, and rs9470080; minimum P = .0004) with the severity of child abuse to predict level of adult PTSD symptoms after correcting for multiple testing. This gene x environment interaction remained significant when controlling for depression severity scores, age, sex, levels of non-child abuse trauma exposure, and genetic ancestry. This genetic interaction was also paralleled by FKBP5 genotype-dependent and PTSD-dependent effects on glucocorticoid receptor sensitivity, measured by the dexamethasone suppression test.

CONCLUSIONS

Four SNPs of the FKBP5 gene interacted with severity of child abuse as a predictor of adult PTSD symptoms. There were no main effects of the SNPs on PTSD symptoms and no significant genetic interactions with level of non-child abuse trauma as predictor of adult PTSD symptoms, suggesting a potential gene-childhood environment interaction for adult PTSD.

Response variation following trauma: a translational neuroscience approach to understanding PTSD

Exposure to traumatic stress is a requirement for the development of posttraumatic stress disorder (PTSD). However, because the majority of trauma-exposed persons do not develop PTSD, examination of the typical effects of a stressor will not identify the critical components of PTSD risk or pathogenesis. Rather, PTSD represents a specific phenotype associated with a failure to recover from the normal effects of trauma. Thus, research must focus on identifying pre- and posttraumatic risk factors that explain the development of the disorder and the failure to reinstate physiological homeostasis. In this review, we summarize what is known about the clinical and biological characteristics of PTSD and articulate some of the gaps in knowledge that can be addressed by basic neuroscience research. We emphasize how knowledge about individual differences related to genetic and epigenetic factors in behavioral and brain responses to stress offers the hope of a deeper understanding of PTSD.

Genetik der Angsterkrankungen

The authors give an overview of the present state of knowledge on the genetics of anxiety disorders. According to ICD-10 or DSM III/IV classification, anxiety disorders comprise panic disorder, generalized anxiety, phobias, and post-traumatic stress disorder. In the context of the conceptual change from psychodynamic anxiety neuroses to complex, multifactorial anxiety disorders, a summary of biological hypotheses of the pathogenesis of anxiety derived from pharmacotherapy, challenge tests, and animal model disorders is provided. The relevant findings from clinical genetic studies (twin and family) and molecular genetic studies (linkage and association) are presented in detail. The most data now available are on panic disorder, though with regard to molecular genetics these are still preliminary. In addition, genetic findings on anxiety as a personality dimension are reviewed, taking into account the present phenotype discussion (category vs dimension). Finally, ethical and therapeutic implications of genetic research on complex, polygenic disorders are discussed.

Commentary: biological findings in PTSD -- too much or too little?

Summarizing the contributions in this section of the book, this chapter addresses questions regarding the complex etiology of PTSD, and the relative strength of discernable biological indicators of the disorder. It outlines two major approaches to exploring the biology of the disorder and discusses the reason for the many non-replications of findings. It defines the constructs of multicausality, equifinality, and multifinality, and evaluates their main implication for studies of PTSD, namely that no biological signal can be properly appraised without taking into account its context. Such context, in PTSD, includes both concurring biological systems and regulatory mechanisms, and environmental-psychosocial input. Studies of gene expression of PTSD exemplify one way of studying the context of putative biological signals. The role of biological alterations as templates for responding to psychosocial challenges is discussed.

Transgenerational transmission of cortisol and PTSD risk

Parental posttraumatic stress disorder (PTSD) appears to be a relevant risk factor for the development of PTSD, as evidenced by a greater prevalence of PTSD, but not trauma exposure, in adult offspring of Holocaust survivors with PTSD, compared to children of Holocaust-exposed parents without PTSD. This paper summarizes recent neuroendocrine studies in offspring of parents with PTSD. Offspring of trauma survivors with PTSD show significantly lower 24-h mean urinary cortisol excretion and salivary cortisol levels as well as enhanced plasma cortisol suppression in response to low dose dexamethasone administration than offspring of survivors without PTSD. In all cases, neuroendocrine measures were negatively correlated with severity of parental PTSD symptoms, even after controlling for PTSD and even other symptoms in offspring. Though the majority of our work has focused on adult offspring of Holocaust survivors, recent observations in infants born to mothers who were pregnant on 9/11 demonstrate that low cortisol in relation to parental PTSD appears to be present early in the course of development and may be influenced by in utero factors such as glucocorticoid programming. Since low cortisol levels are particularly associated with the presence of maternal PTSD the findings suggest the involvement of epigenetic mechanisms.

The genetic background to PTSD

Although extensive research has already been done on the genetic bases of psychiatric disorders, little is known about polygenetic influences in posttraumatic stress disorder (PTSD). This article reviews molecular genetic studies relating to PTSD that were found in a literature search in Medline, Embase and Web of Science. Association studies have investigated 8 major genotypes in connection with PTSD. They have tested hypotheses involving key candidate genes in the serotonin (5-HTT), dopamine (DRD2, DAT), glucocorticoid (GR), GABA (GABRB), apolipoprotein systems (APOE2), brain-derived neurotrophic factor (BDNF) and neuropeptide Y (NPY). The studies have produced inconsistent results, many of which may be attributable to methodological shortcomings and insufficient statistical power. The complex aetiology of PTSD, for which experiencing a traumatic event forms a necessary condition, makes it difficult to identify specific genes that substantially contribute to the disorder. Gene-finding strategies are difficult to apply. Interactions between different genes and between them and the environment probably make certain people vulnerable to developing PTSD. Gene-environmental studies are needed that focus more narrowly on specific, distinct endophenotypes and on influences from environmental factors.

Social Context and the Psychobiology of Posttraumatic Stress

A growing body of research is identifying the molecular and genetic correlates of psychopathology and holds tremendous promise in suggesting the biologic mechanisms that may explain emergent posttraumatic stress disorder (PTSD) phenotypes. Another body of research has begun to consider how elements of the social context may influence the risk of PTSD. It is likely that the social context and molecular/genetic factors jointly determine the risk of PTSD and as such scientific inquiry that considers the interrelationship of these factors stands to advance the field. However, there are particular conceptual and methodologic challenges to conducting and designing studies that adequately assess both the social context and the biologic determinants of PTSD. Much of the current research exploring the biology of PTSD is conducted with highly selective samples that were recruited on the basis of strict phenotypic or medical history criteria. In contrast, population-based sampling represents an opportunity to obtain heterogeneous samples that better represent the population distribution of relevant molecular, genotypic, and phenotypic parameters of interest. These sampling strategies also allow researchers to consider the role of the social context and in turn, how the social context influences the molecular determinants of PTSD. An example of our own work illustrates the feasibility of the population-based sampling approach.

A guide to the genetics of psychiatric disease

The road to scientific discovery begins with an awareness of what is unknown. Research in science can in some ways be like putting together the pieces of a puzzle without having the benefit of the box-top picture of the completed puzzle. The "picture" in science is an understanding of how nature works in a particular instance, and it takes many separate pieces of the "puzzle" to put this understanding together. These pieces are always of different kinds of data, often obtained using different approaches and techniques. The challenge of the researcher is to picture or hypothesize each of the missing pieces before actually having them in hand, so they can be sought and tested in the laboratory. This "picturing" is actually having a clear idea of what you don't know: having a clear image of the "shape" of the missing piece. This is easy when the puzzle surrounding the missing piece is already in hand, but more difficult with less of it constrained by what is already known. In putting paper puzzles together, the shape of the pieces is not the only limitation that needs to be satisfied. There is also the picture to satisfy, that is, the picture usually has to make sense. In science these constraints can be manifold, and usually the quality of the research is judged by the number of ways a piece of data integrates into and brings together the rest of the puzzle. The multidimensionality of scientific questions makes it virtually essential that as many different pieces of the puzzle as possible be obtained. The more that is not known about the puzzle, the more pieces you need. Thus it is with the genetics of psychiatric diseases. In this guide, we will explore as many of the domains of the genetic puzzle as we are aware of. We will learn a bit of the language of each and how they fit into the puzzle with at least one anecdote to serve as an example. Mapping unknown territory is always a process, but we hope this guide will increase the reader's awareness of what is unknown.

Identification of gene markers based on well validated and subcategorized stressed animals for potential clinical applications in PTSD

Post-traumatic stress disorder (PTSD) is a complex mental disorder that can develop in response to traumatic experiences. The molecular mechanisms underlying the pathology of PTSD are poorly understood, and this lack of knowledge hampers our ability to find superior therapeutic approaches to the treatment of this disorder. There are two main reasons for our lack of study in this area: here is no sufficiently validated animal model and lack of large-scale studies for the search of underlying molecular mechanisms. Thus, to promote research on PTSD (especially its molecular mechanisms) and to set molecular basis for searching novel medications of this disorder, large-scale, genome-wide interrogation of a significant amount of genes based upon a well validated animal model is demanded. We hypothesize that a significant number of genes are involved in PTSD. It is only with a large number of these genes identified in specific samples of PTSD-related population, and then it is possible for a sufficient understanding of the pathology at the molecular level of a PTSD, as well as for enhancing the PTSD's therapeutic and preventative strategies. Two prerequisites are needed for testing this hypothesis: (1) relative pure samples from a well validated animal model; and (2) genome-wide screening of PTSD molecular targets. For the animal model, we suggest to use the predator-exposure paradigm, in which rats are exposed to a predator, this model has previously been evaluated behaviorally well emulated the clinical symptoms of PTSD. For a better stringency, three criteria can be used to further validate this animal model: analogous (similarity of behavior), predictive (predictability of drug response) and biological mechanism (e.g., electrophysiological and pathological change in amygdala). For large-scale molecular target screening, the new microarray technology, which can profile expression of tens of thousands genes simultaneously, is the method of choice. The validity and practicability of this hypothesis and the strategy for its testing have been supported by our preliminary laboratory data.

Genetics of fibromyalgia

The pathogenesis of fibromyalgia (FM) and related conditions is not entirely understood. Recent evidence suggests that these syndromes may share heritable pathophysiologic features. Familial studies suggest that genetic and familial factors may play a role in the etiopathogenesis of these conditions. There is evidence that polymorphisms of genes in the serotoninergic and catecholaminergic systems are linked to the pathophysiology of FM and related conditions and are associated with personality traits. The precise role of genetic factors in the etiopathology of FM remains unknown, but it is likely that several genes are operating together to initiate this syndrome. Larger longitudinal studies are needed to better clarify the role of genetics in the development of FM.

Reflective thinking and mental imagery: A perspective on the development of posttraumatic stress disorder

Reflective thinking occurs when information stored in long-term memory (LTM) is not sufficient to allow one to respond "automatically" to an object or event. Instead, stored information must be entered into working memory and a novel response or solution produced. In this article I argue that mental imagery plays a central role in this process, and that over the course of normal cognitive development the process of reflective thinking "programs" LTM so that an increasingly large number of tasks can be performed without reflective thinking. Normal cognitive development thus results in a decreasing reliance on imagery. However, if highly emotional images are formed, additional retrieval cues can be entered into LTM, making such images more likely to occur in the future. Such images induce arousal, similar to that induced by the actual event. This line of thinking leads to a novel perspective on the neurocognitive deficits that underlie the development of posttraumatic stress disorder, and may also help to explain some symptoms seen in hyperactivity, impulsiveness, and difficulties in self-control.