Brain-Derived Neurotropic Factor Val66Met Polymorphism and Posttraumatic Stress Disorder among Survivors of the 1998 Dongting Lake Flood in China

Interaction of Brain-derived Neurotrophic Factor, Exercise, and Fear Extinction: Implications for Post-traumatic Stress Disorder

Brain-Derived Neurotrophic Factor (BDNF) plays an important role in brain development, neural plasticity, and learning and memory. The Val66Met single-nucleotide polymorphism is a common genetic variant that results in deficient activity-dependent release of BDNF. This polymorphism and its impact on fear conditioning and extinction, as well as on symptoms of post-traumatic stress disorder (PTSD), have been of increasing research interest over the last two decades. More recently, it has been demonstrated that regular physical activity may ameliorate impairments in fear extinction and alleviate symptoms in individuals with PTSD via an action on BDNF levels and that there are differential responses to exercise between the Val66Met genotypes. This narrative literature review first describes the theoretical underpinnings of the development and persistence of intrusive and hypervigilance symptoms commonly seen in PTSD and their treatment. It then discusses recent literature on the involvement of BDNF and the Val66Met polymorphism in fear conditioning and extinction and its involvement in PTSD diagnosis and severity. Finally, it investigates research on the impact of physical activity on BDNF secretion, the differences between the Val66Met genotypes, and the effect on fear extinction learning and memory and symptoms of PTSD.

Prevalence of Post-traumatic Stress Disorder After Flood: A Systematic Review and Meta-Analysis

Introduction

Flood as the most common kind of the natural disasters has unpleased short, medium, and long-term consequences on the victims' welfare, relationships, and physical and mental health. One of the most common mental health disorders in these victims is Post-traumatic stress disorder (PTSD). The aim of this study is to investigate the prevalence of PTSD on the flood victims.

Methods

Data resources including PubMed, Scopus, Web of Science, Science Direct, Embase, Google Scholar, conference and congress papers, key journals, the reference list of selected articles as well as systematic reviews were searched to identify studies that reported the prevalence of PTSD in flood victims. Random Effect Model was used to perform meta-analysis of the studies. Cochran test and I2 indicator were used to explore heterogeneity between the studies. Publication bias of the study was evaluated using Begg'test. Data were analyzed by STATA (version 14) software.

Results

After a comprehensive search, 515 papers were extracted. After eliminating duplicates and final screening, 23 studies were selected and entered the meta-analysis phase after qualitative evaluation. The results showed that the prevalence of PTSD in flood victims is 29.48% (95% CI: 18.64-40.31, I2 = 99.3%, p-value < 0.001).

Conclusion

The results of the present study showed that the prevalence of PTSD is relatively high in the flood victims. So, it is necessary to take preventive, supportive, therapeutic and effective actions for them.

Climate change, climate-related disasters and mental disorder in low- and middle-income countries: a scoping review

INTRODUCTION

Climate change and climate-related disasters adversely affect mental health. Low- and middle-income countries (LMICs) are particularly vulnerable to the impacts of climate change and climate-related disasters and often lack adequate mental healthcare infrastructure. We used the scoping review methodology to determine how exposure to climate change and climate-related disasters influences the presence of mental disorders among those living in LMICs. We also aimed to recognise existing gaps in this area of literature.

METHODS

This review followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews checklist. To identify relevant studies, we searched five electronic databases (MEDLINE, EMBASE, Global Health, APA PsycInfo and Sociological Abstracts) from 1 January 2007 to 31 December 2019. We also searched the grey literature. Included studies had an adult-focused LMIC population, a climate change or climate-related disaster exposure and a mental disorder outcome. Relevant study information was extracted and synthesised.

RESULTS

Fifty-eight studies were identified, most of which (n=48) employed a cross-sectional design. The most commonly studied exposure-outcome combinations were flood-related post-traumatic stress disorder (PTSD) (n=28), flood-related depression (n=15) and storm-related PTSD (n=13). The majority of studies identified a positive exposure-outcome association. However, few studies included a baseline or comparator (ie, unexposed) group, thereby limiting our understanding of the magnitude or nature of this association. There was also great heterogeneity in this literature, making studies difficult to pool or compare. Several research gaps were identified including the lack of longitudinal studies and non-uniformity of geographic coverage.

CONCLUSION

To our knowledge, this was the first scoping review to investigate the relationship between climate change and climate-related disaster exposures and mental disorder outcomes in LMICs. Our findings support the need for further research, but also highlight that mental health should be a priority within LMIC climate change policy considerations.

Association of Brain-Derived Neurotrophic Factor rs6265 G>A polymorphism and Post-traumatic Stress Disorder susceptibility: A systematic review and meta-analysis

BACKGROUND

Previous studies have shown that the brain-derived neurotrophic factor (BDNF) rs6265 G > A polymorphism is closely related post-traumatic stress disorder (PTSD) risk. However, the results were not consistent. We therefore conducted a meta-analysis to explore the underlying relationships between BDNF rs6265 G > A polymorphism and PTSD risk.

MATERIALS AND METHODS

Five online databases were searched, and all related studies were reviewed up to July 1, 2020. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated to examine the statistical power of each genetic model. In addition, heterogeneity, sensitivity accumulative analysis, and publication bias were examined to check the statistical power.

RESULT

Overall, 16 publications involving 5,369 subjects were included in this systematic review and 11 case-control studies were analyses in meta-analysis. The pooled results indicated an increasing risk of A allele mutations with PTSD risk. Moreover, the sequential subgroup analysis also demonstrated some similar situations in Asian populations and other groups.

CONCLUSION

Current meta-analysis suggests that the BDNF rs6265 G > A polymorphism might be involved in PTSD susceptibility.

Moderating Effects of BDNF Genetic Variants and Smoking on Cognition in PTSD Veterans

Posttraumatic stress disorder (PTSD) is frequently associated with cognitive disturbances and high prevalence of smoking. This study evaluated cognition in war veterans with PTSD and control subjects, controlled for the effect of smoking and brain derived neurotrophic factor (BDNF) rs6265 and rs56164415 genotypes/alleles. Study included 643 male war veterans with combat related PTSD and 120 healthy controls. Genotyping was done by real time PCR. Cognitive disturbances were evaluated using the Positive and Negative Syndrome Scale (PANSS) cognition subscale and the Rey-Osterrieth Complex Figure (ROCF) test scores. Diagnosis (p < 0.001), BDNF rs56164415 (p = 0.011) and smoking (p = 0.028) were significant predictors of the cognitive decline in subjects with PTSD. BDNF rs56164415 T alleles were more frequently found in subjects with PTSD, smokers and non-smokers, with impaired cognition, i.e., with the higher PANSS cognition subscale scores and with the lower ROCF immediate recall test scores. Presence of one or two BDNF rs56164415 T alleles was related to cognitive decline in PTSD. The T allele carriers with PTSD had advanced cognitive deterioration in smokers and nonsmokers with PTSD, and worse short-term visual memory function. Our findings emphasize the role of the BDNF rs56164415 T allele and smoking in cognitive dysfunction in war veterans with PTSD.

Genetics of resilience: Implications from genome-wide association studies and candidate genes of the stress response system in posttraumatic stress disorder and depression

Resilience is the ability to cope with critical situations through the use of personal and socially mediated resources. Since a lack of resilience increases the risk of developing stress-related psychiatric disorders such as posttraumatic stress disorder (PTSD) and major depressive disorder (MDD), a better understanding of the biological background is of great value to provide better prevention and treatment options. Resilience is undeniably influenced by genetic factors, but very little is known about the exact underlying mechanisms. A recently published genome-wide association study (GWAS) on resilience has identified three new susceptibility loci, DCLK2, KLHL36, and SLC15A5. Further interesting results can be found in association analyses of gene variants of the stress response system, which is closely related to resilience, and PTSD and MDD. Several promising genes, such as the COMT (catechol-O-methyltransferase) gene, the serotonin transporter gene (SLC6A4), and neuropeptide Y (NPY) suggest gene × environment interaction between genetic variants, childhood adversity, and the occurrence of PTSD and MDD, indicating an impact of these genes on resilience. GWAS on PTSD and MDD provide another approach to identifying new disease-associated loci and, although the functional significance for disease development for most of these risk genes is still unknown, they are potential candidates due to the overlap of stress-related psychiatric disorders and resilience. In the future, it will be important for genetic studies to focus more on resilience than on pathological phenotypes, to develop reasonable concepts for measuring resilience, and to establish international cooperations to generate sufficiently large samples.

Influence of childhood trauma and brain-derived neurotrophic factor Val66Met polymorphism on posttraumatic stress symptoms and cortical thickness

Interaction between childhood trauma and genetic factors influences the pathophysiology of posttraumatic stress disorder (PTSD). This study examined the interaction effect of childhood trauma and brain-derived neurotrophic factor (BDNF) Val66Met polymorphism on PTSD symptoms and brain cortical thickness. A total of 216 participants (133 healthy volunteers and 83 PTSD patients) were recruited. T1-weighted structural magnetic resonance imaging, BDNF rs6265 genotyping through blood sampling, and clinical assessments including the childhood trauma questionnaire (CTQ) and posttraumatic stress disorder Checklist (PCL) were performed. A moderated regression analysis, two-way multivariate analysis of covariance, and correlation analysis were conducted. An interaction between the CTQ and the BDNF polymorphism significantly influenced PTSD symptom severity. In fact, people with rs6265 Val/Val genotype and higher CTQ scores showed higher PCL scores. Additionally, this interaction was significant on both left fusiform and transverse temporal gyri thickness. Furthermore, the thickness of both brain regions was significantly correlated with psychological symptoms including depression, anxiety, rumination, and cognitive emotion regulation methods; yet this was mainly observed in people with the Val/Val genotype. The interaction between childhood trauma and BDNF polymorphism significantly influences both PTSD symptoms and cortical thickness and the Val/Val genotype may increase the risk in Korean population.

Behavioral Diversity Across Classic Rodent Models Is Sex-Dependent

Symptoms of trauma and stressor related disorders such as post-traumatic stress disorder (PTSD) often develop well after the traumatic experience has occurred, and so identifying early predictors of risk or resilience is important for the implementation of interventional therapies. For example, passive coping strategies such as tonic immobility and peritraumatic dissociation during the trauma itself are risk factors for the developments of PTSD, especially in women. However, discrete, sex-specific coping responses that predict later outcomes in animal models have not been rigorously defined. Recently, we identified an active, escape-like response exhibited primarily by a subset of female rats in a classic auditory fear conditioning task (“darting”). Here, we asked whether darting during conditioning predicted active responding in a single forced swim (SFS) session to study the potential for darting to reflect a trait-like behavioral strategy that translated across stress models. Male and female Sprague-Dawley (SD) rats were tested in auditory fear conditioning acquisition and memory tests to identify Darters, and then a 15-min SFS 2 weeks later. We observed a significant effect of sex in conditioned freezing behavior, with males exhibiting greater freezing than females across conditioning and testing trials in comparison to females. However, females demonstrated higher velocities in response to shock presentations, and were more likely to exhibit darting behavior in response to the conditioned stimulus (CS). In SFS measures, females engaged in active behaviors such as climbing, head shaking, and diving in greater proportions than males, while males spent more time immobile throughout testing. Despite females exhibiting a more diverse behavioral repertoire in both tests, Darters did not differ from Non-darters in any SFS measure. These results suggest that the propensity to dart does not reflect a simple hyperactivity, and that despite conceptual overlap across the two tests (inescapable stress exposure and the ability to measure active vs. passive coping), the behavioral strategies engaged by an individual animal in each are likely driven by discrete mechanisms. We discuss potential challenges in interpretation of standard behavioral outcomes in classic models across the sexes, and consider the potential need for novel models that better tap into motivational states in females.

Animal models of PTSD: a challenge to be met

Recent years have seen increased interest in psychopathologies related to trauma exposure. Specifically, there has been a growing awareness to posttraumatic stress disorder (PTSD) in part due to terrorism, climate change-associated natural disasters, the global refugee crisis, and increased violence in overpopulated urban areas. However, notwithstanding the increased awareness to the disorder, the increasing number of patients, and the devastating impact on the lives of patients and their families, the efficacy of available treatments remains limited and highly unsatisfactory. A major scientific effort is therefore devoted to unravel the neural mechanisms underlying PTSD with the aim of paving the way to developing novel or improved treatment approaches and drugs to treat PTSD. One of the major scientific tools used to gain insight into understanding physiological and neuronal mechanisms underlying diseases and for treatment development is the use of animal models of human diseases. While much progress has been made using these models in understanding mechanisms of conditioned fear and fear memory, the gained knowledge has not yet led to better treatment options for PTSD patients. This poor translational outcome has already led some scientists and pharmaceutical companies, who do not in general hold opinions against animal models, to propose that those models should be abandoned. Here, we critically examine aspects of animal models of PTSD that may have contributed to the relative lack of translatability, including the focus on the exposure to trauma, overlooking individual and sex differences, and the contribution of risk factors. Based on findings from recent years, we propose research-based modifications that we believe are required in order to overcome some of the shortcomings of previous practice. These modifications include the usage of animal models of PTSD which incorporate risk factors and of the behavioral profiling analysis of individuals in a sample. These modifications are aimed to address factors such as individual predisposition and resilience, thus taking into consideration the fact that only a fraction of individuals exposed to trauma develop PTSD. We suggest that with an appropriate shift of practice, animal models are not only a valuable tool to enhance our understanding of fear and memory processes, but could serve as effective platforms for understanding PTSD, for PTSD drug development and drug testing.

Prevalence of posttraumatic stress disorder among road traffic accident survivors: A PRISMA-compliant meta-analysis

BACKGROUND

Involvement in road traffic accidents (RTAs) may put individuals at increased risk for a wide range of psychiatric disorders, among which posttraumatic stress disorder (PTSD) presents a public health issue. However, a great disparity was observed among studies exploring the prevalence of PTSD among RTA survivors. This meta-analysis aimed to explore the pooled prevalence of PTSD among RTA survivors.

METHODS

Electronic databases of PubMed, Embase, Web of Science, PsycARTICLES, PsycINFO, and CINAHL were searched to identify relevant studies. Study selection and data extraction were conducted independently by 2 investigators, and a meta-analysis was performed to synthesize the data. Heterogeneity among studies was evaluated using the Cochran Q test and quantified using the I statistic. Subgroup analyses were performed to identify the source of the heterogeneity. The possibility of publication bias was assessed using Egger linear test.

RESULTS

Fifteen eligible studies containing 6804 RTA survivors were identified in this meta-analysis, of which 1489 were identified with PTSD. The pooled prevalence of PTSD among RTA survivors was 22.25% (95% confidence interval: 16.71%-28.33%). A high degree of heterogeneity was observed across studies (I = 97.1%, P < .001), with reported PTSD prevalence ranging from 6.3% to 58.3%. Subgroup analyses found that the prevalence of PTSD among RTA survivors varied significantly across studies in relation to the instrument used to assess PTSD, country, race, gender, and education level (P < .05).

CONCLUSION

The high pooled prevalence of PTSD among RTA survivors found in this study significantly underscores the need for providing timely and effective intervention strategies for RTA survivors.

Comorbidity of post-traumatic stress disorder and anxiety in flood survivors: Prevalence and shared risk factors

Post-traumatic stress disorder (PTSD) and anxiety are both prevalent in trauma-related populations. However, comorbidity of these 2 psychiatric disorders has not been investigated in flood survivors. This study aimed to estimate the extent to which PTSD and anxiety co-occur in flood survivors, and identify shared risk factors for PTSD only and comorbidity of PTSD and anxiety.Individuals who experienced Dongting Lake flood in 1998 were enrolled in this study using stratified and systematic random sampling method. Information on social support, personality traits, PTSD, and anxiety was collected using self-report questionnaires. The intensity of exposure to the flood was measured by some questions. Logistic regression analyses were used to identify factors associated with PTSD only and comorbidity of PTSD and anxiety.In all, 325 participants were enrolled in this study. The prevalence of PTSD, anxiety, and comorbidity of PTSD and anxiety among survivors of the 1998 Dongting Lake flood at 17-year follow-up was 9.54%, 9.23%, and 6.15%, respectively. Furthermore, 64.52% of those with PTSD had anxiety and 66.67% of those with anxiety had PTSD. Loss of relative, injury of body, damage of house, and emotional instability were shared risk factors for PTSD only and comorbidity of PTSD and anxiety, in comparison with neither PTSD nor anxiety.Post-traumatic stress disorder only and comorbidity of PTSD and anxiety are prevalent in flood survivors, and are both related to the intensity of exposure to the flood and personality traits, indicating that integrated intervention strategies of PTSD and anxiety for flood survivors are needed.

The Effects of a BDNF Val66Met Polymorphism on Posttraumatic Stress Disorder: A Meta-Analysis

OBJECTIVE

Given evidence that posttraumatic stress disorder (PTSD) is moderately heritable, a number of studies utilizing candidate gene approaches have attempted to examine the potential contributions of theoretically relevant genetic variation. Some of these studies have found sup port for a brain-derived neurotrophic factor (BDNF) variant, Val66Met, in the risk of developing PTSD, while others have failed to find this link.

METHODS

This study sought to reconcile these conflicting findings using a meta-analysis framework. Analyses were also used to determine whether there is significant heterogeneity in the link between this variant and PTSD. We conducted a systematic review of the literature on BDNF and PTSD from the PsycINFO and PubMed databases. A total of 11 studies were included in the analysis.

RESULTS

Findings indicate a marginally significant effect of the BDNF Val66Met variant on PTSD (p < 0.1). However, of the 11 studies included, only 2 suggested an effect with a non-zero confidence interval, one of which showed a z score of 3.31. We did not find any evidence for heterogeneity.

CONCLUSIONS

Findings from this meta-analytic investigation of the published literature provide little support for the Val66Met variant of BDNF as a predictor of PTSD. Future well-powered agnostic genome-wide association studies with more refined phenotyping are needed to clarify genetic influences on PTSD.