Genetics of anxiety and trauma-related disorders

Psychedelic therapies reconsidered: compounds, clinical indications, and cautious optimism

The clinical investigation of psychedelic medicines has blossomed over the last 5 years. Data from a Phase 3 industry trial and a multicenter Phase 2 industry trial, in addition to multiple early phase investigator-initiated and industry trials, have now been published in peer-reviewed journals. This narrative review summarizes both the recent data and the current clinical trials that are being conducted with various classes of "psyche-manifesting" substances, which may prove beneficial in the treatment of a broad range of conditions. Methodological considerations, unique challenges, and next steps for research are discussed in keeping with the uniquely "experiential" nature of these therapies.

Developmental Pathways from Childhood Maltreatment to Young Adult Romantic Relationship Functioning

Childhood abuse has been suggested to potentiate a maladaptive developmental trajectory, leaving adolescents and young adults at risk for mental health and romantic relationship problems. It has been suggested that mental health problems mediate the relationship between childhood abuse and young adult romantic relationship functioning; however, there are few prospective studies. The objective of the current study was to examine the effects of childhood physical, sexual, and emotional abuse on posttraumatic stress symptoms in adolescence, and relationship quality, intimacy, companionship, and conflict in young adult's romantic relationships. Using data from the Longitudinal Studies of Childhood Abuse and Neglect (LONGSCAN), a sample of 313 racially diverse adolescents were used. Using structural equation modeling, it was found that dissociation mediated the relationship between physical abuse and relationship quality, but in the opposite direction of what was expected. Additionally, anger mediated the relationship from both physical and sexual abuse to conflict. Childhood abuse appears to influence young adult relationship functioning through mental health problems in mid-adolescence, particularly anger and dissociation. These results are consistent with the notion that children who were abused may struggle in romantic relationships in young adulthood and addressing mental health problems in adolescence may a point of intervention.

Protective Factors Associated With Fewer Generalized Anxiety Disorder Symptoms Among Women Exposed to Intimate Partner Violence

Generalized anxiety disorder (GAD) has received minimal empirical attention in the context of intimate partner violence (IPV). Furthermore, factors related to lower levels of GAD symptoms in this population have received limited focus. This study evaluated the protective role of four forms of support, spiritual, family, friend, and community, in predicting levels of generalized anxiety among women who have experienced recent IPV. Participants included 116 women who were recruited from local agencies serving IPV-exposed individuals. Participants completed measures of IPV, GAD, stressful life events, spiritual support, social support, and community support during a 1-hr interview. Findings from a hierarchical multiple regression analysis indicated that after accounting for age, income, mental health service utilization, stressful life events, and severity of IPV, lower GAD symptoms were only associated with higher spiritual support (β = -0.20, p = .02) and community support (β = -0.25, p = .01), not friend or family support, F(9, 114) = 5.10; p < .001; R² = .30. These findings indicate that alternative sources of support (i.e., spiritual and community) may be more accessible for IPV-exposed women, contributing to their association with reduced GAD symptomatology. The current study highlights the potential for spiritual and community support to serve a beneficial role above and beyond standard social support proffered by friends and family on symptoms of GAD. Results reinforce the examination of a broad range of multiple supports among women experiencing IPV. This thorough examination of different support systems may provide further insight into novel resources that can be strengthened among IPV-exposed populations.

Social losses predict a faster onset and greater severity of obsessive-compulsive disorder

BACKGROUND

While stressful life events increase the risk of developing a range of psychiatric disorders, including obsessive-compulsive disorder (OCD), their ability to precipitate specific obsessive-compulsive symptoms' dimensions is unknown. Here we aimed to evaluate the potential role of three different types of stressful life events, herein termed losses (death of a loved one, termination of a romantic relationship and severe illness) in predicting the speed of progression from subclinical to clinical OCD and the severity of specific OCD dimensions in a large multicentre OCD sample.

METHODS

Nine hundred and fifty-four OCD outpatients from the Brazilian OCD Research Consortium were included in this study. Several semi-structured and structured instruments were used, including the Structured Clinical Interview for DSM-IV Axis I Disorders, the Yale-Brown Obsessive-Compulsive Scale, the Dimensional Yale-Brown Obsessive-Compulsive Scale, the Brown Assessment of Beliefs Scale, the Beck Depression Inventory, the Beck Anxiety Inventory and the Yale OCD Natural History Questionnaire. Regression models investigated the interaction between types of loss and gender to predict speed of progression from subclinical obsessive-compulsive symptoms to OCD, and the severity of five symptom dimensions.

RESULTS

While termination of a relationship was associated with a faster speed of progression from subthreshold to clinical OCD, the death of a loved one was associated with increased severity of hoarding symptoms. There was also an interaction between gender and experiences of death, which predicted a faster speed of progression to OCD in males.

CONCLUSIONS

Stressful life events have the ability to accelerate the progression from subclinical to clinical OCD, as well as impact the severity of specific OCD dimensions. Gender also plays a role in both the progression and severity of symptoms. These findings suggest that stressful life events may represent a marker to identify individuals at risk of progressing to clinical OCD.

Genome-wide translational profiling of amygdala Crh-expressing neurons reveals role for CREB in fear extinction learning

Fear and extinction learning are adaptive processes caused by molecular changes in specific neural circuits. Neurons expressing the corticotropin-releasing hormone gene (Crh) in central amygdala (CeA) are implicated in threat regulation, yet little is known of cell type-specific gene pathways mediating adaptive learning. We translationally profiled the transcriptome of CeA Crh-expressing cells (Crh neurons) after fear conditioning or extinction in mice using translating ribosome affinity purification (TRAP) and RNAseq. Differential gene expression and co-expression network analyses identified diverse networks activated or inhibited by fear vs extinction. Upstream regulator analysis demonstrated that extinction associates with reduced CREB expression, and viral vector-induced increased CREB expression in Crh neurons increased fear expression and inhibited extinction. These findings suggest that CREB, within CeA Crh neurons, may function as a molecular switch that regulates expression of fear and its extinction. Cell-type specific translational analyses may suggest targets useful for understanding and treating stress-related psychiatric illness.

Vesicular monoamine transporter 2 mediates fear behavior in mice

A subset of people exposed to a traumatic event develops post-traumatic stress disorder (PTSD), which is associated with dysregulated fear behavior. Genetic variation in SLC18A2, the gene that encodes vesicular monoamine transporter 2 (VMAT2), has been reported to affect risk for the development of PTSD in humans. Here, we use transgenic mice that express either 5% (VMAT2-LO mice) or 200% (VMAT2-HI mice) of wild-type levels of VMAT2 protein. We report that VMAT2-LO mice have reduced VMAT2 protein in the hippocampus and amygdala, impaired monoaminergic vesicular storage capacity in both the striatum and frontal cortex, decreased monoamine metabolite abundance and a greatly reduced capacity to release dopamine upon stimulation. Furthermore, VMAT2-LO mice showed exaggerated cued and contextual fear expression, altered fear habituation, inability to discriminate threat from safety cues, altered startle response compared with wild-type mice and an anxiogenic-like phenotype, but displayed no deficits in social function. By contrast, VMAT2-HI mice exhibited increased VMAT2 protein throughout the brain, higher vesicular storage capacity and greater dopamine release upon stimulation compared with wild-type controls. Behaviorally, VMAT2-HI mice were similar to wild-type mice in most assays, with some evidence of a reduced anxiety-like responses. Together, these data show that presynaptic monoamine function mediates PTSD-like outcomes in our mouse model, and suggest a causal link between reduced VMAT2 expression and fear behavior, consistent with the correlational relationship between VMAT2 genotype and PTSD risk in humans. Targeting this system is a potential strategy for the development of pharmacotherapies for disorders like PTSD.

Role of MicroRNAs in Anxiety and Anxiety-Related Disorders

MicroRNAs as critical regulators of gene expression important for functions including neuronal development, synapse formation, and synaptic plasticity have been linked with the regulation of neurobiological systems that underlie anxiety processing in the brain. In this chapter, we give an update on associative evidence linking regulation of microRNAs with anxiety- and trauma-related disorders. Moving beyond correlative research, functional studies have emerged recently that explore causal relationships between microRNA expression and anxiety-like behavior. It has been demonstrated that experimental up- or downregulation of the candidate microRNAs in important nodes of the anxiety neurocircuitry can indeed modulate anxiety-related behavior in animal models. Improved methodologies for assessing microRNA-mediated modulation have aided such functional studies, revealing a number of anxiety-regulating microRNAs including miR-15a, miR-17-92, miR-34, miR-101, miR-124, miR-135, and miR-155. Important functional target genes of these identified microRNAs are associated with specific neurotransmitter/neuromodulator signaling, neurotrophin (e.g., BDNF) expression and other aspects of synaptic plasticity, as well as with stress-regulatory/hypothalamic-pituitary-axis function. Furthermore, microRNAs have been revealed that are regulated in distinct brain regions following various anxiety-attenuating strategies. These include pharmacological treatments such as antidepressants and other drugs, as well as non-pharmacological interventions such as fear extinction/exposure therapy or positive stimuli such as exposure to environmental enrichment. These are first indications for a role for microRNAs in the mechanism of action of anxiolytic treatments. As research continues, there is much hope that a deeper understanding of the microRNA-mediated mechanisms underlying anxiety-related disorders could open up possibilities for future novel biomarker and treatment strategies.

Fear Processing, Psychophysiology, and PTSD

The processing and regulation of fear is one of the key components of posttraumatic stress disorder (PTSD). Fear can involve both acute and potential threats that can manifest in different behaviors and result from activity within different neural nodes and networks. Fear circuits have been studied extensively in animal models for several decades and in human neuroimaging research for almost 20 years. Therefore, the centrality of fear processing to PTSD lends the disorder to be more tractable to investigation at the level of brain and behavior, and provides several observable phenotypes that can be linked to PTSD symptoms. Moreover, psychophysiological metrics of fear conditioning offer tools that can be used to shift diagnostic paradigms in psychiatry toward neurobiology-consistent with a Research Domain Criteria approach to PTSD. In general, mammalian fear processing can be divided into fear learning (or acquisition), during which an association develops between previously neutral stimuli and aversive outcomes, and fear extinction, in which the latter associations are suppressed by a new form of learning. This review describes translational research in both fear acquisition and extinction, along with their relevance to PTSD and PTSD treatment, focusing specifically on the empirical value and potential clinical utility of psychophysiological methods.

The effects of childhood maltreatment and anxiety proneness on neuropsychological test performance in non-clinical older adolescents

BACKGROUND

The effect of childhood maltreatment (CM) on neuropsychological performance is well established, but the effect of anxiety proneness (AP) on such performance has been underexplored. We assessed the predictive ability of CM and AP, and their interaction, in non-clinical adolescents, for a range of previously documented neuropsychological deficits.

METHODS

Multiple linear regression models were used to assess the unique and combined influences of CM and AP on neuropsychological performance in 104 non-clinical adolescents, who underwent both neuropsychiatric and neuropsychological assessment.

RESULTS

The interaction of CM and AP was associated with poorer performance in executive functioning skills, processing speed, and estimated IQ. CM and AP were uniquely associated with verbal working memory performance, while verbal and visual memory performance and learning, and visuo-spatial ability, were not associated with either CM, AP or the interaction of CM and AP.

LIMITATIONS

The use of self-report measures to determine participants' levels of CM, AP, and depression. The CTQ-SF, a retrospective self-report measure, may have introduced recall bias. The neuropsychological evaluation was not conducted in the Xhosa language, the first language of most African participants. Most instruments utilized have not been validated in a South African adolescent sample. The impact of important moderator variables (e.g., age of onset of maltreatment) was not assessed.

CONCLUSIONS

Increased levels of CM and AP may be risk markers for poor performance in several key neuropsychological domains. Our findings underscore the importance of assessing the impact of both CM and anxiety-related temperamental traits on neuropsychological performance.

COMT val158met polymorphism links to altered fear conditioning and extinction are modulated by PTSD and childhood trauma

BACKGROUND

Risk for posttraumatic stress disorder (PTSD) is thought to be mediated by gene × environment (G × E) interactions that affect core cognitive processes such as fear learning. The catechol-O-methyltransferase (COMT) val158met polymorphism has been associated with risk for PTSD and impaired fear inhibition. We used a large, relatively homogenous population to (1) replicate previous findings of poor fear inhibition in COMT Met/Met carriers with PTSD; (2) determine if COMT association with fear inhibition is moderated by childhood trauma (CT), an environmental risk factor for PTSD; and (3) determine if COMT is associated with altered fear processes after recent exposure to combat trauma.

METHODS

Male Marines and Navy Corpsmen of European-American ancestry were assessed prior to (n = 714) and 4-6 months after deployment to Afghanistan (n = 452). Acquisition and extinction of fear-potentiated startle, childhood and combat trauma history, and PTSD diagnosis were assessed at both time points.

RESULTS

Before deployment, Met/Met genotype was associated with fear inhibition deficits in participants with current PTSD; however, this association was dependent on CT exposure. After deployment, combat trauma was associated with a modest reduction in fear extinction in Met/Met compared with Val/Val carriers. There were no associations of COMT genotype with fear extinction within healthy and non-traumatized individuals.

CONCLUSIONS

These findings support the hypothesis that G × E interactions underlie associations of COMT val158met with fear inhibition deficits. These studies confirm that Met/Met carriers with PTSD have poor fear inhibition, and support further research in understanding how this polymorphism might impact response to extinction-based therapies.

Serotonin transporter 5-HTTLPR genotype is associated with intrusion and avoidance symptoms of DSM-5 posttraumatic stress disorder (PTSD) in Chinese earthquake survivors

BACKGROUND AND OBJECTIVES

Prior studies have found that the serotonin transporter gene-linked polymorphic region (5-HTTLPR) interacts with trauma exposure to increase general risk for Posttraumatic Stress Disorder (PTSD). However, there is little knowledge about the effects of the interaction on distinct symptom clusters of PTSD. This study aimed to investigate the relation between the interaction of 5-HTTLPR and earthquake-related exposures and a contemporary phenotypic model of DSM-5 PTSD symptoms in a traumatised adult sample from China.

DESIGN

A cross-sectional design with gene-environment interaction (G × E) approach was adopted.

METHODS

Participants were 1131 survivors who experienced 2008 Wenchuan earthquake. PTSD symptoms were assessed with the PTSD Checklist for DSM-5 (PCL-5). The 5-HTTLPR polymorphism was genotyped with capillary electrophoresis (CE) in ABI 3730xl genetic Analyzer.

RESULTS

Although there was no significant interaction between 5-HTTLPR and traumatic exposure on total PTSD symptoms, respondents with the LL genotype of 5-HTTLPR who were highly exposed to the earthquake experienced lower intrusion and avoidance symptoms than those with the S-allele carriers.

CONCLUSIONS

The findings suggest that the 5-HTTLPR may have an important impact on the development of PTSD and add to the extant knowledge on understanding and treating of posttraumatic psychopathology.

Stress-related disorders, pituitary adenylate cyclase-activating peptide (PACAP)ergic system, and sex differences

Trauma-related disorders, such as posttraumatic stress disorder (PTSD) are remarkably common and debilitating, and are often characterized by dysregulated threat responses. Across numerous epidemiological studies, females have been found to have an approximately twofold increased risk for PTSD and other stress-related disorders. Understanding the biological mechanisms of this differential risk is of critical importance. Recent data suggest that the pituitary adenylate cyclase-activating polypeptide (PACAP) pathway is a critical regulator of the stress response across species. Moreover, increasing evidence suggests that this pathway is regulated by both stress and estrogen modulation and may provide an important window into understanding mechanisms of sex differences in the stress response. We have recently shown that PACAP and its receptor (PAC1R) are critical mediators of abnormal processes after psychological trauma. Notably, in heavily traumatized human subjects, there appears to be a robust sex-specific association of PACAP blood levels and PAC1R gene variants with fear physiology, PTSD diagnosis, and symptoms, specifically in females. The sex-specific association occurs within a single-nucleotide polymorphism (rs2267735) that resides in a putative estrogen response element involved in PAC1R gene regulation. Complementing these human data, the PAC1R messenger RNA is induced with fear conditioning or estrogen replacement in rodent models. These data suggest that perturbations in the PACAP-PAC1R pathway are regulated by estrogen and are involved in abnormal fear responses underlying PTSD.

Negative Mood and Obsessive-Compulsive Related Clinical Constructs: An Examination of Underlying Factors

Emerging evidence suggests that many of the clinical constructs used to help understand and explain obsessive-compulsive (OC) symptoms, and negative mood, may be causally interrelated. One approach to understanding this interrelatedness is a motivational systems approach. This approach suggests that rather than considering clinical constructs and negative affect as separable entities, they are all features of an integrated threat management system, and as such are highly coordinated and interdependent. The aim of the present study was to examine if clinical constructs related to OC symptoms and negative mood are best treated as separable or, alternatively, if these clinical constructs and negative mood are best seen as indicators of an underlying superordinate variable, as would be predicted by a motivational systems approach. A sample of 370 student participants completed measures of mood and the clinical constructs of inflated responsibility, intolerance of uncertainty, not just right experiences, and checking stop rules. An exploratory factor analysis suggested two plausible factor structures, one where all construct items and negative mood items loaded onto one underlying superordinate variable, and a second structure comprising of five factors, where each item loaded onto a factor representative of what the item was originally intended to measure. A confirmatory factor analysis showed that the five factor model was preferential to the one factor model, suggesting the four constructs and negative mood are best conceptualized as separate variables. Given the predictions of a motivational systems approach were not supported in the current study, other possible explanations for the causal interrelatedness between clinical constructs and negative mood are discussed.

Allostatic load and comorbidities: A mitochondrial, epigenetic, and evolutionary perspective

Stress-related pathophysiology drives comorbid trajectories that elude precise prediction. Allostatic load algorithms that quantify biological "wear and tear" represent a comprehensive approach to detect multisystemic disease processes of the mind and body. However, the multiple morbidities directly or indirectly related to stress physiology remain enigmatic. Our aim in this article is to propose that biological comorbidities represent discrete pathophysiological processes captured by measuring allostatic load. This has applications in research and clinical settings to predict physical and psychiatric comorbidities alike. The reader will be introduced to the concepts of allostasis, allostasic states, allostatic load, and allostatic overload as they relate to stress-related diseases and the proposed prediction of biological comorbidities that extend rather to understanding psychopathologies. In our transdisciplinary discussion, we will integrate perspectives related to (a) mitochondrial biology as a key player in the allostatic load time course toward diseases that "get under the skin and skull"; (b) epigenetics related to child maltreatment and biological embedding that shapes stress perception throughout lifespan development; and

miR-34b attenuates trauma-induced anxiety-like behavior by targeting CRHR1

Exposure to trauma is a potential contributor to anxiety; however, the molecular mechanisms responsible for trauma-induced anxiety require further clarification. In this study, in an aim to explore these mechanisms, we observed the changes in the hypothalamic pituitary adrenal (HPA) axis using a radioimmunoassay and the changes in anxiety-like behavior using the open field test and elevated plus maze test in a rat model following intervention with NBI-27914, a specific corticotropin-releasing hormone receptor 1 (CRHR1) antagonist. CRHR1 was found to be involved in trauma-induced anxiety. We then applied bioinformatic analysis to screen microRNAs (miRNAs or miRs) that target CRHR1, and miR-34b was determined to negatively regulate CRHR1 mRNA in primary hypothalamic neurons. The overexpression of miR-34b in the paraventricular nucleus (PVN) by a miRNA agomir using a drug delivery system decreased the hyperactivity of the HPA axis and anxiety-like behavior. Overall, the involvement of the HPA axis in trauma-induced anxiety was demonstrated, and trauma-induced anxiety was attenuated by decreasing the hyperactivity of the HPA axis via miR-34b by targeting CRHR1.

Endocannabinoid signalling modulates susceptibility to traumatic stress exposure

Stress is a ubiquitous risk factor for the exacerbation and development of affective disorders including major depression and posttraumatic stress disorder. Understanding the neurobiological mechanisms conferring resilience to the adverse consequences of stress could have broad implications for the treatment and prevention of mood and anxiety disorders. We utilize laboratory mice and their innate inter-individual differences in stress-susceptibility to demonstrate a critical role for the endogenous cannabinoid 2-arachidonoylglycerol (2-AG) in stress-resilience. Specifically, systemic 2-AG augmentation is associated with a stress-resilient phenotype and enhances resilience in previously susceptible mice, while systemic 2-AG depletion or CB1 receptor blockade increases susceptibility in previously resilient mice. Moreover, stress-resilience is associated with increased phasic 2-AG-mediated synaptic suppression at ventral hippocampal-amygdala glutamatergic synapses and amygdala-specific 2-AG depletion impairs successful adaptation to repeated stress. These data indicate amygdala 2-AG signalling mechanisms promote resilience to adverse effects of acute traumatic stress and facilitate adaptation to repeated stress exposure.

Decreased Glutamatergic Activity in the Frontal Cortex of Single Prolonged Stress Model: In vivo and Ex Vivo Proton MR Spectroscopy

Single prolonged stress (SPS) is one of the preclinical models of posttraumatic stress disorder (PTSD) in humans. Not every traumatized person develops PTSD and the onset of the disease varies from months to many years after exposure to life-threatening events. The pathogenetic neurometabolites in PTSD have not been investigated to date, and could provide a means for therapeutic interventions. Therefore the present study aimed to evaluate neurochemical changes in the frontal cortex in the SPS model during time-dependent sensitization using in vivo and ex vivo proton magnetic spectroscopy (¹H-MRS). Twenty-one male Sprague-Dawley rats (200-220 g) were randomly assigned into two groups (Control, n = 10; SPS, n = 11). SPS consists of three consecutive stressors (restraint, forced swimming, and ether exposure) followed by 7 days without disturbance. In vivo ¹H-MRS scans were conducted at baseline, immediately after SPS, and 3 and 7 days after SPS to quantify time-dependent alterations in the frontal cortex. On day 7, all animals were sacrificed and ex vivo ¹H-MRS was performed. After SPS exposure, the SPS group showed signs of excitatory activities (glutamate) and cellular membrane turnover (choline and total choline) for 7 days. After the time-sensitization period, the SPS group showed lower glutamate and creatine levels and higher choline and lactate levels than the control group. These results indicate that SPS induces sustained adaptation of glutamatergic neuronal activity in the frontal cortex. Therefore, we conclude that SPS-induced stress reduces glutamatergic metabolism in the frontal cortex.

Forebrain glutamatergic, but not GABAergic, neurons mediate anxiogenic effects of the glucocorticoid receptor

Anxiety disorders constitute a major disease and social burden worldwide; however, many questions concerning the underlying molecular mechanisms still remain open. Besides the involvement of the major excitatory (glutamate) and inhibitory (gamma aminobutyric acid (GABA)) neurotransmitter circuits in anxiety disorders, the stress system has been directly implicated in the pathophysiology of these complex mental illnesses. The glucocorticoid receptor (GR) is the major receptor for the stress hormone cortisol (corticosterone in rodents) and is widely expressed in excitatory and inhibitory neurons, as well as in glial cells. However, currently it is unknown which of these cell populations mediate GR actions that eventually regulate fear- and anxiety-related behaviors. In order to address this question, we generated mice lacking the receptor specifically in forebrain glutamatergic or GABAergic neurons by breeding GR^flox/flox mice to Nex-Cre or Dlx5/6-Cre mice, respectively. GR deletion specifically in glutamatergic, but not in GABAergic, neurons induced hypothalamic-pituitary-adrenal axis hyperactivity and reduced fear- and anxiety-related behavior. This was paralleled by reduced GR-dependent electrophysiological responses in the basolateral amygdala (BLA). Importantly, viral-mediated GR deletion additionally showed that fear expression, but not anxiety, is regulated by GRs in glutamatergic neurons of the BLA. This suggests that pathological anxiety likely results from altered GR signaling in glutamatergic circuits of several forebrain regions, while modulation of fear-related behavior can largely be ascribed to GR signaling in glutamatergic neurons of the BLA. Collectively, our results reveal a major contribution of GRs in the brain's key excitatory, but not inhibitory, neurotransmitter system in the regulation of fear and anxiety behaviors, which is crucial to our understanding of the molecular mechanisms underlying anxiety disorders.

Genetic approaches for the study of PTSD: Advances and challenges

Post-traumatic stress disorder (PTSD) is a highly debilitating stress and anxiety-related disorder that occurs in response to specific trauma or abuse. Genetic risk factors may account for up to 30-40% of the heritability of PTSD. Understanding the gene pathways that are associated with PTSD, and how those genes interact with the fear and stress circuitry to mediate risk and resilience for PTSD will enable the development of targeted therapies to prevent the occurrence of or decrease the severity of this complex multi-gene disorder. This review will summarize recent research on genetic approaches to understanding PTSD risk and resilience in human populations, including candidate genes and their epigenetic modifications, genome-wide association studies and neural imaging genetics approaches. Despite challenges faced within this field of study such as inconsistent results and replications, genetic approaches still offer exciting opportunities for the identification and development of novel therapeutic targets and therapies in the future.

The Association of Cigarette Smoking With Depression and Anxiety: A Systematic Review

BACKGROUND

Many studies report a positive association between smoking and mental illness. However, the literature remains mixed regarding the direction of this association. We therefore conducted a systematic review evaluating the association of smoking and depression and/or anxiety in longitudinal studies.

METHODS

Studies were identified by searching PubMed, Scopus, and Web of Science and were included if they: (1) used human participants, (2) were longitudinal, (3) reported primary data, (4) had smoking as an exposure and depression and/or anxiety as an outcome, or (5) had depression and/or anxiety as the exposure and smoking as an outcome.

RESULTS

Outcomes from 148 studies were categorized into: smoking onset, smoking status, smoking heaviness, tobacco dependence, and smoking trajectory. The results for each category varied substantially, with evidence for positive associations in both directions (smoking to later mental health and mental health to later smoking) as well as null findings. Overall, nearly half the studies reported that baseline depression/anxiety was associated with some type of later smoking behavior, while over a third found evidence that a smoking exposure was associated with later depression/anxiety. However, there were few studies directly supporting a bidirectional model of smoking and anxiety, and very few studies reporting null results.

CONCLUSIONS

The literature on the prospective association between smoking and depression and anxiety is inconsistent in terms of the direction of association most strongly supported. This suggests the need for future studies that employ different methodologies, such as Mendelian randomization (MR), which will allow us to draw stronger causal inferences.

IMPLICATIONS

We systematically reviewed longitudinal studies on the association of different aspects of smoking behavior with depression and anxiety. The results varied considerably, with evidence for smoking both associated with subsequent depression and anxiety, and vice versa. Few studies supported a bidirectional relationship, or reported null results, and no clear patterns by gender, ethnicity, clinical status, length to follow-up, or diagnostic test. Suggesting that despite advantages of longitudinal studies, they cannot alone provide strong evidence of causality. Therefore, future studies investigating this association should employ different methods allowing for stronger causal inferences to be made, such as MR.

Stress-related disorders, pituitary adenylate cyclase-activating peptide (PACAP)ergic system, and sex differences

Trauma-related disorders, such as posttraumatic stress disorder (PTSD) are remarkably common and debilitating, and are often characterized by dysregulated threat responses. Across numerous epidemiological studies, females have been found to have an approximately twofold increased risk for PTSD and other stress-related disorders. Understanding the biological mechanisms of this differential risk is of critical importance. Recent data suggest that the pituitary adenylate cyclase-activating polypeptide (PACAP) pathway is a critical regulator of the stress response across species. Moreover, increasing evidence suggests that this pathway is regulated by both stress and estrogen modulation and may provide an important window into understanding mechanisms of sex differences in the stress response. We have recently shown that PACAP and its receptor (PAC1R) are critical mediators of abnormal processes after psychological trauma. Notably, in heavily traumatized human subjects, there appears to be a robust sex-specific association of PACAP blood levels and PAC1R gene variants with fear physiology, PTSD diagnosis, and symptoms, specifically in females. The sex-specific association occurs within a single-nucleotide polymorphism (rs2267735) that resides in a putative estrogen response element involved in PAC1R gene regulation. Complementing these human data, the PAC1R messenger RNA is induced with fear conditioning or estrogen replacement in rodent models. These data suggest that perturbations in the PACAP-PAC1R pathway are regulated by estrogen and are involved in abnormal fear responses underlying PTSD.

Oxidative Stress Implications in the Affective Disorders: Main Biomarkers, Animal Models Relevance, Genetic Perspectives, and Antioxidant Approaches

The correlation between the affective disorders and the almost ubiquitous pathological oxidative stress can be described in a multifactorial way, as an important mechanism of central nervous system impairment. Whether the obvious changes which occur in oxidative balance of the affective disorders are a part of the constitutive mechanism or a collateral effect yet remains as an interesting question. However it is now clear that oxidative stress is a component of these disorders, being characterized by different aspects in a disease-dependent manner. Still, there are a lot of controversies regarding the relevance of the oxidative stress status in most of the affective disorders and despite the fact that most of the studies are showing that the affective disorders development can be correlated to increased oxidative levels, there are various studies stating that oxidative stress is not linked with the mood changing tendencies. Thus, in this minireview we decided to describe the way in which oxidative stress is involved in the affective disorders development, by focusing on the main oxidative stress markers that could be used mechanistically and therapeutically in these deficiencies, the genetic perspectives, some antioxidant approaches, and the relevance of some animal models studies in this context.

Targeting the endocannabinoid system to treat anxiety-related disorders

The endocannabinoid system plays an important role in the control of emotions, and its dysregulation has been implicated in several psychiatric disorders. The most common self-reported reason for using cannabis is rooted in its ability to reduce feelings of stress, tension, and anxiety. Nevertheless, there are only few studies in controlled clinical settings that confirm that administration of cannabinoids can benefit patients with a post-traumatic stress disorder (PTSD). There are considerable encouraging preclinical data to suggest that endocannabinoid-targeted therapeutics for anxiety disorders should continue. In this review, we will describe data supporting a role for the endocannabinoid system in preventing and treating anxiety-like behavior in animal models and PTSD patients. Cannabinoids have shown beneficial outcomes in rat and mouse models of anxiety and PTSD, but they also may have untoward effects that discourage their chronic usage, including anxiogenic effects. Hence, clinical and preclinical research on the endocannabinoid system should further study the effects of cannabinoids on anxiety and help determine whether the benefits of using exogenous cannabinoids outweigh the risks. In general, this review suggests that targeting the endocannabinoid system represents an attractive and novel approach to the treatment of anxiety-related disorders and, in particular, PTSD.

Neural Mechanism of a Sex-Specific Risk Variant for Posttraumatic Stress Disorder in the Type I Receptor of the Pituitary Adenylate Cyclase Activating Polypeptide

BACKGROUND

Posttraumatic stress disorder (PTSD) is a frequent anxiety disorder with higher prevalence rates in female patients than in male patients (2.5:1). Association with a single nucleotide polymorphism (rs2267735) in the gene ADCYAP1R1 encoding the type I receptor (PAC1-R) of the pituitary adenylate cyclase activating polypeptide has been reported with PTSD in female patients. We sought to identify the neural correlates of the described PAC1-R effects on associative learning.

METHODS

In a reverse genetic approach, we examined two independent healthy samples (N1 = 112, N2 = 73) using functional magnetic resonance imaging during cued and contextual fear conditioning. Skin conductance responses and verbal self-reports of arousal, valence, and contingency were recorded.

RESULTS

We found that PAC1-R modulates the blood oxygenation level-dependent response of the hippocampus. Specifically, we observed decreased hippocampal activity during contextual, but not during cued, fear conditioning in female participants carrying the PAC1-R risk allele. We observed no significant differences in conditionability for skin conductance responses, verbal reports, or activation in other brain regions between the genotype groups in female participants.

CONCLUSIONS

Our results suggest that impaired contextual conditioning in the hippocampal formation may mediate the association between PAC1-R and PTSD symptoms. Our findings potentially identify a missing link between the involvement of PAC1-R in PTSD and the well-established structural and functional hippocampal deficits in these patients.

Sex differences in the shared genetics of dimensions of self-reported depression and anxiety

BACKGROUND

The prevalence of depression and anxiety symptoms and their comorbidity varies between males and females for reasons still unknown. This study aims to test whether differences between males and females in self-reported symptoms and their covariation are caused by variations in the magnitude of genetic and environmental factors.

METHODS

750 monozygotic and dizygotic healthy twin pairs (18-60 years; M=39.77 years) participated in the TWIN-E project. Univariate and multivariate genetic modelling was undertaken using the Depression Anxiety Stress Scale (DASS-42).

RESULTS

Additive genetics and unique environment contributed to self-reported depression (heritability, h(2): 34%), anxiety (h(2): 30%) and stress (h(2): 34%) scores in univariate models, and to the common latent factor (h(2): 39%) in the multivariate model. No sex differences in magnitude of estimates for DASS-42 scores were found in the univariate model. However when considering correlated depression and anxiety symptomatology only shared genetic factors between depression and anxiety contributed to depression scores in males, but both specific and shared genetic factors contributed to depression scores in females.

LIMITATIONS

The results are limited to the sample of healthy, community, adult, same sex twin pairs who participated in the study.

CONCLUSIONS

Differences in males and females in genetic aetiology of self-reported dimensions of depression are only apparent when taking into consideration the covariation with self-reported anxiety. This difference is highlighted by the finding that both common and specific genetic factors contribute to self-reported depression in females but not males. This novel finding may help explain the increased incidence of depression symptoms in females.

Genome-wide association study of posttraumatic stress disorder in a cohort of Iraq-Afghanistan era veterans

BACKGROUND

Posttraumatic stress disorder (PTSD) is a psychiatric disorder that can develop after experiencing traumatic events. A genome-wide association study (GWAS) design was used to identify genetic risk factors for PTSD within a multi-racial sample primarily composed of U.S. veterans.

METHODS

Participants were recruited at multiple medical centers, and structured interviews were used to establish diagnoses. Genotypes were generated using three Illumina platforms and imputed with global reference data to create a common set of SNPs. SNPs that increased risk for PTSD were identified with logistic regression, while controlling for gender, trauma severity, and population substructure. Analyses were run separately in non-Hispanic black (NHB; n = 949) and non-Hispanic white (NHW; n = 759) participants. Meta-analysis was used to combine results from the two subsets.

RESULTS

SNPs within several interesting candidate genes were nominally significant. Within the NHB subset, the most significant genes were UNC13C and DSCAM. Within the NHW subset, the most significant genes were TBC1D2, SDC2 and PCDH7. In addition, PRKG1 and DDX60L were identified through meta-analysis. The top genes for the three analyses have been previously implicated in neurologic processes consistent with a role in PTSD. Pathway analysis of the top genes identified alternative splicing as the top GO term in all three analyses (FDR q < 3.5 × 10(-5)).

LIMITATIONS

No individual SNPs met genome-wide significance in the analyses.

CONCLUSIONS

This multi-racial PTSD GWAS identified biologically plausible candidate genes and suggests that post-transcriptional regulation may be important to the pathology of PTSD; however, replication of these findings is needed.

Genomic predictors of combat stress vulnerability and resilience in U.S. Marines: A genome-wide association study across multiple ancestries implicates PRTFDC1 as a potential PTSD gene

BACKGROUND

Research on the etiology of post-traumatic stress disorder (PTSD) has rapidly matured, moving from candidate gene studies to interrogation of the entire human genome in genome-wide association studies (GWAS). Here we present the results of a GWAS performed on samples from combat-exposed U.S. Marines and Sailors from the Marine Resiliency Study (MRS) scheduled for deployment to Iraq and/or Afghanistan. The MRS is a large, prospective study with longitudinal follow-up designed to identify risk and resiliency factors for combat-induced stress-related symptoms. Previously implicated PTSD risk loci from the literature and polygenic risk scores across psychiatric disorders were also evaluated in the MRS cohort.

METHODS

Participants (N=3494) were assessed using the Clinician-Administered PTSD Scale and diagnosed using the DSM-IV diagnostic criterion. Subjects with partial and/or full PTSD diagnosis were called cases, all other subjects were designated controls, and study-wide maximum CAPS scores were used for longitudinal assessments. Genomic DNA was genotyped on the Illumina HumanOmniExpressExome array. Individual genetic ancestry was determined by supervised cluster analysis for subjects of European, African, Hispanic/Native American, and other descent. To test for association of SNPs with PTSD, logistic regressions were performed within each ancestry group and results were combined in meta-analyses. Measures of childhood and adult trauma were included to test for gene-by-environment (GxE) interactions. Polygenic risk scores from the Psychiatric Genomic Consortium were used for major depressive disorder (MDD), bipolar disorder (BPD), and schizophrenia (SCZ).

RESULTS

The array produced >800K directly genotyped and >21M imputed markers in 3494 unrelated, trauma-exposed males, of which 940 were diagnosed with partial or full PTSD. The GWAS meta-analysis identified the phosphoribosyl transferase domain containing 1 gene (PRTFDC1) as a genome-wide significant PTSD locus (rs6482463; OR=1.47, SE=0.06, p=2.04×10(-9)), with a similar effect across ancestry groups. Association of PRTFDC1 with PTSD in an independent military cohort showed some evidence for replication. Loci with suggestive evidence of association (n=25 genes, p<5×10(-6)) further implicated genes related to immune response and the ubiquitin system, but these findings remain to be replicated in larger GWASs. A replication analysis of 25 putative PTSD genes from the literature found nominally significant SNPs for the majority of these genes, but associations did not remain significant after correction for multiple comparison. A cross-disorder analysis of polygenic risk scores from GWASs of BPD, MDD, and SCZ found that PTSD diagnosis was associated with risk sores of BPD, but not with MDD or SCZ.

CONCLUSIONS

This first multi-ethnic/racial GWAS of PTSD highlights the potential to increase power through meta-analyses across ancestry groups. We found evidence for PRTFDC1 as a potential novel PTSD gene, a finding that awaits further replication. Our findings indicate that the genetic architecture of PTSD may be determined by many SNPs with small effects, and overlap with other neuropsychiatric disorders, consistent with current findings from large GWAS of other psychiatric disorders.

A role for Tac2, NkB, and Nk3 receptor in normal and dysregulated fear memory consolidation

The centromedial amygdala (CeM), a subdivision of the central amygdala (CeA), is believed to be the main output station of the amygdala for fear expression. We provide evidence that the Tac2 gene, expressed by neurons specifically within the CeM, is required for modulating fear memories. Tac2 is colocalized with GAD65 and CaMKIIα but not with PKCd and Enk neurons in the CeM. Moreover, the Tac2 product, NkB, and its specific receptor, Nk3R, are also involved in the consolidation of fear memories. Increased Tac2 expression, through a stress-induced PTSD-like model, or following lentiviral CeA overexpression, are sufficient to enhance fear consolidation. This effect is blocked by the Nk3R antagonist osanetant. Concordantly, silencing of Tac2-expressing neurons in CeA with DREADDs impairs fear consolidation. Together, these studies further our understanding of the role of the Tac2 gene and CeM in fear processing and may provide approaches to intervention for fear-related disorders.

Altered hippocampal function before emotional trauma in rats susceptible to PTSD-like behaviors

Posttraumatic stress disorder (PTSD) is an anxiety disorder that occurs after experiencing a traumatic event. Susceptibility to PTSD exists, as only some trauma-exposed individuals develop this condition. Investigating susceptibilities in animal models can contribute to understanding the etiology of the disorder. We previously reported an animal model which allows reliable pre-classification of rats as susceptible (Sus) or resistant (Res) to developing a PTSD-like phenotype after a later trauma. Here we report that Sus, compared to Res, rats have altered hippocampal function, along the septo-temporal axis, prior to experiencing a traumatic event. In Experiment I, Res and Sus rats explored a novel box twice. Using a cellular imaging method for assessing plasticity-related immediate-early gene expression in large neuronal ensembles, Arc/Homer1a catFISH, we show that Sus rats have smaller vCA3 ensembles during the second exploration. This suppressed vCA3 activation in Sus rats was not due to a difference in exploratory behavior, or to a difference in Arc/Homer1a expression in the basolateral amygdala (BLA). BLA is a main source of inputs to vCA3, but both the ensemble size and overlap of BLA ensembles activated during the two explorations was similar to that of Res rats. Additionally, Sus rats had significant 'infidelity' in their dorsal hippocampal representations of the second event: a lower overlap, compared to Res rats, of Arc/Homer1a-expressing ensembles activated during the two explorations (the size of the ensembles were similar to those of Res rats). These differences were revealed only in conditions of relatively low stress, because they were not observed when Sus and Res rats experienced fear conditioning (Experiment II). Combined, the findings show that altered hippocampal function exists before experiencing emotional trauma in susceptible rats and suggest that this is a risk factor for PTSD.

Genetic approaches to understanding post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is increasingly recognized as both a disorder of enormous mental health and societal burden, but also as an anxiety disorder that may be particularly understandable from a scientific perspective. Specifically, PTSD can be conceptualized as a disorder of fear and stress dysregulation, and the neural circuitry underlying these pathways in both animals and humans are becoming increasingly well understood. Furthermore, PTSD is the only disorder in psychiatry in which the initiating factor, the trauma exposure, can be identified. Thus, the pathophysiology of the fear and stress response underlying PTSD can be examined and potentially interrupted. Twin studies have shown that the development of PTSD following a trauma is heritable, and that genetic risk factors may account for up to 30-40% of this heritability. A current goal is to understand the gene pathways that are associated with PTSD, and how those genes act on the fear/stress circuitry to mediate risk vs. resilience for PTSD. This review will examine gene pathways that have recently been analysed, primarily through candidate gene studies (including neuroimaging studies of candidate genes), in addition to genome-wide associations and the epigenetic regulation of PTSD. Future and on-going studies are utilizing larger and collaborative cohorts to identify novel gene candidates through genome-wide association and other powerful genomic approaches. Identification of PTSD biological pathways strengthens the hope of progress in the mechanistic understanding of a model psychiatric disorder and allows for the development of targeted treatments and interventions.

Oxytocin's role in anxiety: a critical appraisal

A growing literature suggests that the oxytocin (OT) system may play a role in human anxiety states, anxiety-related traits, and moreover, that this system may be a target for the development of novel anxiolytic treatments. However, studies of OT's acute and chronic effects on various aspects of anxiety have produced mixed results. In this forward-looking review, we discuss the myriad phenomena to which the term "anxiety" is applied in the OT literature and the problem this presents developing a coherent picture of OT's role in anxiety. We then survey several different fields of research that support the role of the OT system in human anxiety, including evolutionary perspectives, translational and neuroimaging research, genetic studies, and clinical trials of intranasal OT. As an outgrowth of this data, we propose a "bowtie" model of OT's role at the interface of social attachment and anxiety. We next direct attention to understudied brain regions and neural circuits which may be important to study in OT experiments in humans anxiety disorders. Finally, we conclude by proposing questions and priorities for studying both the clinical potential of OT in anxiety, as well as mechanisms that may underlie this potential. Crucially, these priorities include targeted proof-of-concept clinical trials of IN OT in certain anxiety disorders, including investigations of individual moderators of OT's anxiolytic effects (i.e. sex, genetic factors, and early experience). This article is part of a Special Issue entitled Oxytocin and Social Behav.

Zebrafish as an emerging model for studying complex brain disorders

The zebrafish (Danio rerio) is rapidly becoming a popular model organism in pharmacogenetics and neuropharmacology. Both larval and adult zebrafish are currently used to increase our understanding of brain function, dysfunction, and their genetic and pharmacological modulation. Here we review the developing utility of zebrafish in the analysis of complex brain disorders (including, e.g., depression, autism, psychoses, drug abuse, and cognitive deficits), also covering zebrafish applications towards the goal of modeling major human neuropsychiatric and drug-induced syndromes. We argue that zebrafish models of complex brain disorders and drug-induced conditions are a rapidly emerging critical field in translational neuroscience and pharmacology research.

Unpredictable neonatal stress enhances adult anxiety and alters amygdala gene expression related to serotonin and GABA

Anxiety-related disorders are among the most common psychiatric illnesses, thought to have both genetic and environmental causes. Early-life trauma, such as abuse from a caregiver, can be predictable or unpredictable, each resulting in increased prevalence and severity of a unique set of disorders. In this study, we examined the influence of early unpredictable trauma on both the behavioral expression of adult anxiety and gene expression within the amygdala. Neonatal rats were exposed to unpaired odor-shock conditioning for 5 days, which produces deficits in adult behavior and amygdala dysfunction. In adulthood, we used the Light/Dark box test to measure anxiety-related behaviors, measuring the latency to enter the lit area and quantified urination and defecation. The amygdala was then dissected and a microarray analysis was performed to examine changes in gene expression. Animals that had received early unpredictable trauma displayed significantly longer latencies to enter the lit area and more defecation and urination. The microarray analysis revealed over-represented genes related to learning and memory, synaptic transmission and trans-membrane transport. Gene ontology and pathway analysis identified highly represented disease states related to anxiety phenotypes, including social anxiety, obsessive-compulsive disorders, post-traumatic stress disorder and bipolar disorder. Addiction-related genes were also overrepresented in this analysis. Unpredictable shock during early development increased anxiety-like behaviors in adulthood with concomitant changes in genes related to neurotransmission, resulting in gene expression patterns similar to anxiety-related psychiatric disorders.

Translational reciprocity: bridging the gap between preclinical studies and clinical treatment of stress effects on the adolescent brain

The genetic, biological, and environmental backgrounds of an organism fundamentally influence the balance between risk and resilience to stress. Sex, age, and environment transact with responses to trauma in ways that can mitigate or exacerbate the likelihood that post-traumatic stress disorder will develop. Translational approaches to modeling affective disorders in animals will ultimately provide novel treatments and a better understanding of the neurobiological underpinnings behind these debilitating disorders. The extant literature on trauma/stress has focused predominately on limbic and cortical structures that innervate the hypothalamic-pituitary-adrenal axis and influence glucocorticoid-mediated negative feedback. It is through these neuroendocrine pathways that a self-perpetuating fear memory can propagate the long-term effects of early life trauma. Recent work incorporating translational approaches has provided novel pathways that can be influenced by early life stress, such as the glucocorticoid receptor chaperones, including FKBP51. Animal models of stress have differing effects on behavior and endocrine pathways; however, complete models replicating clinical characteristics of risk and resilience have not been rigorously studied. This review discusses a four-factor model that considers the importance of studying both risk and resilience in understanding the developmental response to trauma/stress. Consideration of the multifactorial nature of clinical populations in the design of preclinical models and the application of preclinical findings to clinical treatment approaches comprise the core of translational reciprocity, which is discussed in the context of the four-factor model.

Maternal anxiety and infants' hippocampal development: timing matters

Exposure to maternal anxiety predicts offspring brain development. However, because children's brains are commonly assessed years after birth, the timing of such maternal influences in humans is unclear. This study aimed to examine the consequences of antenatal and postnatal exposure to maternal anxiety upon early infant development of the hippocampus, a key structure for stress regulation. A total of 175 neonates underwent magnetic resonance imaging (MRI) at birth and among them 35 had repeated scans at 6 months of age. Maternal anxiety was assessed using the State-Trait Anxiety Inventory (STAI) at week 26 of pregnancy and 3 months after delivery. Regression analyses showed that antenatal maternal anxiety did not influence bilateral hippocampal volume at birth. However, children of mothers reporting increased anxiety during pregnancy showed slower growth of both the left and right hippocampus over the first 6 months of life. This effect of antenatal maternal anxiety upon right hippocampal growth became statistically stronger when controlling for postnatal maternal anxiety. Furthermore, a strong positive association between postnatal maternal anxiety and right hippocampal growth was detected, whereas a strong negative association between postnatal maternal anxiety and the left hippocampal volume at 6 months of life was found. Hence, the postnatal growth of bilateral hippocampi shows distinct responses to postnatal maternal anxiety. The size of the left hippocampus during early development is likely to reflect the influence of the exposure to perinatal maternal anxiety, whereas right hippocampal growth is constrained by antenatal maternal anxiety, but enhanced in response to increased postnatal maternal anxiety.

PAC1 receptor (ADCYAP1R1) genotype is associated with PTSD's emotional numbing symptoms in Chinese earthquake survivors

BACKGROUND

Genetic factors are important in the development of posttraumatic stress disorder (PTSD) following exposure to traumatic events. However, the molecular genetic underpinnings of this disorder remain largely unresolved. The present study investigated the association between ADCYAP1R1 rs2267735 genotype and PTSD symptoms in a highly traumatized sample of Chinese adults.

METHODS

Participants included 326 victims who experienced 2008 Wenchuan earthquake and lost their children during the disaster. PTSD symptoms were assessed with the PTSD Checklist (PCL). The ADCYAP1R1 rs2267735 SNP was genotyped with the Sequenom iPlex chemistries and the MassARRAY system.

RESULTS

The results indicated that although the rs2267735 'CC' genotype was not associated with total PTSD symptoms, it could significantly predict severity of PTSD's emotional numbing symptoms in women.

LIMITATIONS

A relatively small sample exposed to specific traumatic events was used, and PTSD was assessed using a self-reported instrument.

CONCLUSIONS

The findings suggest that the PACAP-PAC1 receptor pathway may play an important role in female human responses to traumatic stress, and carry implications for better understanding and treating of posttraumatic psychopathology.

The co-occurrence of common mental and physical disorders within Australian families: a national population-based study

OBJECTIVE

Because comorbidity between mental and physical disorders is commonly found in patients, it would be expected that this pattern would also be reflected at the family level. During a recent population-based survey of common mental disorders, respondents were asked about the presence of selected mental and physical disorders in their relatives. The aim of this research was to describe the within-family co-occurrence of selected common physical and mental disorders in a population-based sample.

METHODS

Subjects were drawn from the Australian National Survey of Mental Health and Wellbeing 2007. A modified version of the World Mental Health Survey Initiative of the Composite International Diagnostic Interview (WMH-CIDI 3.0, henceforth CIDI) was used to identify lifetime-ever common psychiatric disorders (anxiety disorders, depression, drug or alcohol disorders). The respondents were asked if any of their relatives had one of a list of psychiatric (anxiety, bipolar disorder, depression, drug or alcohol problem, schizophrenia) or general physical disorders (cancer, heart problems, intellectual disability, memory problems). We examined the relationship between the variables of interest using logistic regression, adjusting for potential confounding factors.

RESULTS

Compared to otherwise-well respondents, those who had a CIDI diagnosis of major depressive disorders, anxiety disorders, or drug or alcohol abuse/dependence were significantly more likely to have first-degree relatives with (a) the same diagnosis as the respondent, (b) other mental disorders not identified in the respondent, and (c) a broad range of general physical conditions.

CONCLUSIONS

Individuals with common mental disorders report greater familial co-occurrence for a range of mental and physical disorders. When eliciting family histories, clinicians should remain mindful that both mental and physical disorders can co-occur within families.

A causal model of post-traumatic stress disorder: disentangling predisposed from acquired neural abnormalities

Discriminating neural abnormalities into the causes versus consequences of psychopathology would enhance the translation of neuroimaging findings into clinical practice. By regarding the traumatic encounter as a reference point for disease onset, neuroimaging studies of post-traumatic stress disorder (PTSD) can potentially allocate PTSD neural abnormalities to either predisposing (pre-exposure) or acquired (post-exposure) factors. Based on novel research strategies in PTSD neuroimaging, including genetic, environmental, twin, and prospective studies, we provide a causal model that accounts for neural abnormalities in PTSD, and outline its clinical implications. Current data suggest that abnormalities within the amygdala and dorsal anterior cingulate cortex represent predisposing risk factors for developing PTSD, whereas dysfunctional hippocampal-ventromedial prefrontal cortex (vmPFC) interactions may become evident only after having developed the disorder.

Differential Genetic and Epigenetic Regulation of catechol-O-methyltransferase is Associated with Impaired Fear Inhibition in Posttraumatic Stress Disorder

The catechol-O-methyltransferase (COMT) enzyme is critical for the catabolic regulation of synaptic dopamine, resulting in altered cortical functioning. The COMT Val¹⁵⁸Met polymorphism has been implicated in human mental illness, with Met/Met homozygotes associated with increased susceptibility to posttraumatic stress disorder (PTSD). Our primary objective was to examine the intermediate phenotype of fear inhibition in PTSD stratified by COMT genotype (Met/Met, Val/Met, and Val/Val) and differential gene regulation via methylation status at CpG sites in the COMT promoter region. More specifically, we examined the potential interaction of COMT genotype and PTSD diagnosis on fear-potentiated startle during fear conditioning and extinction and COMT DNA methylation levels (as determined using genomic DNA isolated from whole blood). Participants were recruited from medical and gynecological clinics of an urban hospital in Atlanta, GA, USA. We found that individuals with the Met/Met genotype demonstrated higher fear-potentiated startle to the CS− (safety signal) and during extinction of the CS+ (danger signal) compared to Val/Met and Val/Val genotypes. The PTSD+ Met/Met genotype group had the greatest impairment in fear inhibition to the CS− (p = 0.006), compared to Val carriers. In addition, the Met/Met genotype was associated with DNA methylation at four CpG sites, two of which were associated with impaired fear inhibition to the safety signal. These results suggest that multiple differential mechanisms for regulating COMT function – at the level of protein structure via the Val¹⁵⁸Met genotype and at the level of gene regulation via differential methylation – are associated with impaired fear inhibition in PTSD.

Current status on behavioral and biological markers of PTSD: a search for clarity in a conflicting literature

Extensive research has identified stereotypic behavioral and biological abnormalities in post-traumatic stress disorder (PTSD), such as heightened autonomic activity, an exaggerated startle response, reduced basal cortisol levels and cognitive impairments. We have reviewed primary research in this area, noting that factors involved in the susceptibility and expression of PTSD symptoms are more complex and heterogeneous than is commonly stated, with extensive findings which are inconsistent with the stereotypic behavioral and biological profile of the PTSD patient. A thorough assessment of the literature indicates that interactions among myriad susceptibility factors, including social support, early life stress, sex, age, peri- and post-traumatic dissociation, cognitive appraisal of trauma, neuroendocrine abnormalities and gene polymorphisms, in conjunction with the inconsistent expression of the disorder across studies, confounds attempts to characterize PTSD as a monolithic disorder. Overall, our assessment of the literature addresses the great challenge in developing a behavioral and biomarker-based diagnosis of PTSD.

Towards new approaches to disorders of fear and anxiety

Fear and anxiety are debilitating conditions that affect a significant number of individuals in their lifetimes. Understanding underlying mechanisms of these disorders affords us the possibility of therapeutic intervention. Such clarity in terms of mechanism and intervention can only come from an amalgamation of research from human to animal studies that attempt to mimic the human condition, both of which are discussed in this review. We begin by presenting an outline of our current understanding of the neurobiological basis of fear and anxiety. This outline spans various levels of organization that include the circuitry, molecular pathways, genetic and epigenetic components of fear and anxiety. Using these organizational levels as a scaffold, we then discuss strategies that are currently used to ameliorate these disorders, and forecast future interventions that hold therapeutic promise. Among these newer promising treatments, we include, optogenetic, pharmacological, and extinction-based approaches, as well as lifestyle modifications, with combinatorial treatment regimens of these holding the most promise.

The genetic factors influencing the development of trichotillomania

Trichotillomania (TTM), an obsessive-compulsive spectrum disorder (OCSD), is a psychiatric condition characterized by repetitive hair pulling. Evidence from family and twin studies suggest a heritable link of TTM. Functional polymorphisms in genes involved in neuronal pathways might influence the susceptibility to TTM. This review is an attempt to compile the genetic factors reported to modify the development of TTM.

Individual differences in recovery from traumatic fear

Although exposure to major psychological trauma is unfortunately common, risk for related neuropsychiatric conditions, such as post-traumatic stress disorder (PTSD), varies greatly among individuals. Fear extinction offers a tractable and translatable behavioral readout of individual differences in learned recovery from trauma. Studies in rodent substrains and subpopulations are providing new insights into neural system dysfunctions associated with impaired fear extinction. Rapid progress is also being made in identifying key molecular circuits, epigenetic mechanisms, and gene variants associated with differences in fear extinction. Here, we discuss how this research is informing understanding of the etiology and pathophysiology of individual differences in risk for trauma-related anxiety disorders, and how future work can help identify novel diagnostic biomarkers and pharmacotherapeutics for these disorders.

Fear extinction and BDNF: translating animal models of PTSD to the clinic

Brain-derived neurotrophic factor (BDNF) is the most studied neurotrophin involved in synaptic plasticity processes that are required for long-term learning and memory. Specifically, BDNF gene expression and activation of its high-affinity tropomyosin-related kinase B (TrkB) receptor are necessary in the amygdala, hippocampus and prefrontal cortex for the formation of emotional memories, including fear memories. Among the psychiatric disorders with altered fear processing, there is post-traumatic stress disorder (PTSD) which is characterized by an inability to extinguish fear memories. Since BDNF appears to enhance extinction of fear, targeting impaired extinction in anxiety disorders such as PTSD via BDNF signalling may be an important and novel way to enhance treatment efficacy. The aim of this review is to provide a translational point of view that stems from findings in the BDNF regulation of synaptic plasticity and fear extinction. In addition, there are different systems that seem to alter fear extinction through BDNF modulation like the endocannabinoid system and the hypothalamic-pituitary adrenal axis. Recent work also finds that the pituitary adenylate cyclase-activating polypeptide and PAC1 receptor, which are upstream of BDNF activation, may be implicated in PTSD. Especially interesting are data that exogenous fear extinction enhancers such as antidepressants, histone deacetylases inhibitors and D-cycloserine, a partial N-methyl d-aspartate agonist, may act through or in concert with the BDNF-TrkB system. Finally, we review studies where recombinant BDNF and a putative TrkB agonist, 7,8-dihydroxyflavone, may enhance extinction of fear. These approaches may lead to novel agents that improve extinction in animal models and eventually humans.

Acute and posttraumatic stress symptoms in a prospective gene x environment study of a university campus shooting

CONTEXT

The serotonin transporter (SLC6A4) has been associated with several stress-related syndromes including posttraumatic stress disorder (PTSD). The ability to detect meaningful associations is largely dependent on reliable measures of preexisting trauma.

OBJECTIVE

To study the association of genetic variants within SLC6A4 with acute and posttraumatic stress symptoms in a civilian cohort with known levels of preexisting trauma and PTSD symptoms collected prior to a shared index traumatic event.

DESIGN

Ongoing longitudinal study.

SETTING

On February 14, 2008, a lone gunman shot multiple people on the campus of Northern Illinois University in DeKalb, Illinois, killing 5 and wounding 21. As part of an ongoing longitudinal study on that campus, a cohort of female undergraduate students, interviewed prior to the shooting, completed follow-up trauma-related measures including PTSD symptom severity (follow-up survey was launched 17 days postshooting; n = 691). To obtain DNA, salivary samples were collected from a subset of the original study population based on willingness to participate (n = 276).

PARTICIPANTS

Two hundred four undergraduate women.

MAIN OUTCOME MEASURES

SLC6A4 polymorphisms STin2, 5-HTTLPR, and rs25531 were genotyped in 235 individuals.

RESULTS

We found that although the STin2 variant and 5-HTTLPR alone did not associate with increased PTSD symptoms, rs25531 and the 5-HTTLPR multimarker genotype (combined 5-HTTLPR and rs25531) were associated with significantly increased acute stress disorder symptoms at 2 to 4 weeks postshooting (n = 161; P < .05). This association remained significant when controlling for race and for level of shooting exposure (n = 123; P < .007). The association was most robust with the 5-HTTLPR multimarker genotype and avoidance symptoms (P = .003).

CONCLUSION

These data suggest that differential function of the serotonin transporter may mediate differential response to a severe trauma. When examined in a relatively homogenous sample with shared trauma and known prior levels of child and adult trauma, the 5-HTTLPR multimarker genotype may serve as a useful predictor of risk for PTSD-related symptoms in the weeks and months following the trauma.

Catechol-O-methyltransferase Val158Met polymorphism moderates anterior cingulate volume in posttraumatic stress disorder

BACKGROUND

Posttraumatic stress disorder (PTSD) is associated with structural and functional compromise of the anterior cingulate cortex (ACC), which may in turn be associated with impairment of its ability to regulate the amygdala. The Val158Met polymorphism in the catechol-O-methyltransferase gene, which substantially influences dopamine inactivation in the frontal lobe in general and in ACC in particular, may moderate ACC integrity in PTSD.

METHODS

We tested this hypothesis in a sample of Vietnam and Persian Gulf War veterans who experienced substantial military operational stress, including 51 who met criteria for PTSD and 48 matched controls who did not.

RESULTS

Participants with PTSD were previously reported to have smaller ACC volumes than controls in this sample. A novel repeated-measures analysis of variance was conducted with PTSD diagnosis, Val158Met genotype, and their interaction predicting left and right ACC volume. Genotype was not directly related to ACC volume, but it did significantly interact with the PTSD diagnosis. The difference in ACC volume between the participants without PTSD and participants with PTSD was greater among individuals homozygous for the Val allele than among carriers of the Met allele. This finding was driven largely by the right ACC. Analyses of Caucasian-only, non-Caucasian-only, and male-only subsamples indicated similar patterns.

CONCLUSIONS

Our findings suggest Val158Met genotype moderates the effect of PTSD-related processes on right ACC volume.

Interpersonal stress regulation and the development of anxiety disorders: an attachment-based developmental framework

Anxiety disorders represent a common but often debilitating form of psychopathology in both children and adults. While there is a growing understanding of the etiology and maintenance of these disorders across various research domains, only recently have integrative accounts been proposed. While classical attachment history has been a traditional core construct in psychological models of anxiety, contemporary attachment theory has the potential to integrate neurobiological and behavioral findings within a multidisciplinary developmental framework. The current paper proposes a modern attachment theory-based developmental model grounded in relevant literature from multiple disciplines including social neuroscience, genetics, neuroendocrinology, and the study of family factors involved in the development of anxiety disorders. Recent accounts of stress regulation have highlighted the interplay between stress, anxiety, and activation of the attachment system. This interplay directly affects the development of social-cognitive and mentalizing capacities that are acquired in the interpersonal context of early attachment relationships. Early attachment experiences are conceptualized as the key organizer of a complex interplay between genetic, environmental, and epigenetic contributions to the development of anxiety disorders - a multifactorial etiology resulting from dysfunctional co-regulation of fear and stress states. These risk-conferring processes are characterized by hyperactivation strategies in the face of anxiety. The cumulative allostatic load and subsequent "wear and tear" effects associated with hyperactivation strategies converge on the neural pathways of anxiety and stress. Attachment experiences further influence the development of anxiety as potential moderators of risk factors, differentially impacting on genetic vulnerability and relevant neurobiological pathways. Implications for further research and potential treatments are outlined.