Genetic and environmental influences on alpha amylase stress reactivity and shared genetic covariation with cortisol

Salivary alpha amylase (sAA) is a common measure of stress reactivity, primarily reflecting sympathetic nervous system activity. Salivary cortisol is also a reliable, frequently used biomarker of stress and reflects the hypothalamic-pituitary-adrenal (HPA) axis response. This study examined heritability across varying metrics of sAA in response to a social evaluative stressor, the Trier Social Stress Test (TSST). The goal of this study was to estimate genetic and environmental influences on measurements of sAA stress reactivity. Moreover, we evaluated the shared genetic covariation between sAA and cortisol. Participants included twins aged 15-20 years (54% female). We measured alpha amylase and cortisol reactivity to the TSST via serial salivary cortisol samples collected pre- and post-TSST. Modest to moderate heritability estimates (11-64%) were observed across measures purported to capture alpha amylase stress reactivity (peak, area under the curve, baseline-to-peak change). Findings also indicate that sAA baseline and peak are primarily influenced by a shared genetic factor. There was no evidence of shared genetic influences between sAA and cortisol. These findings suggest the genetic control of the HPA and Sympathetic Adreno-Medullar axis are genetically independent of one another despite both playing a role in response to stressors.

Differences in genetic correlations between posttraumatic stress disorder and alcohol-related problems phenotypes compared to alcohol consumption-related phenotypes

BACKGROUND

Posttraumatic Stress Disorder (PTSD) tends to co-occur with greater alcohol consumption as well as alcohol use disorder (AUD). However, it is unknown whether the same etiologic factors that underlie PTSD-alcohol-related problems comorbidity also contribute to PTSD- alcohol consumption.

METHODS

We used summary statistics from large-scale genome-wide association studies (GWAS) of European-ancestry (EA) and African-ancestry (AA) participants to estimate genetic correlations between PTSD and a range of alcohol consumption-related and alcohol-related problems phenotypes.

RESULTS

In EAs, there were positive genetic correlations between PTSD phenotypes and alcohol-related problems phenotypes (e.g. Alcohol Use Disorders Identification Test (AUDIT) problem score) (rGs: 0.132-0.533, all FDR adjusted p < 0.05). However, the genetic correlations between PTSD phenotypes and alcohol consumption -related phenotypes (e.g. drinks per week) were negatively associated or non-significant (rGs: -0.417 to -0.042, FDR adjusted p: <0.05-NS). For AAs, the direction of correlations was sometimes consistent and sometimes inconsistent with that in EAs, and the ranges were larger (rGs for alcohol-related problems: -0.275 to 0.266, FDR adjusted p: NS, alcohol consumption-related: 0.145-0.699, FDR adjusted p: NS).

CONCLUSIONS

These findings illustrate that the genetic associations between consumption and problem alcohol phenotypes and PTSD differ in both strength and direction. Thus, the genetic factors that may lead someone to develop PTSD and high levels of alcohol consumption are not the same as those that lead someone to develop PTSD and alcohol-related problems. Discussion around needing improved methods to better estimate heritabilities and genetic correlations in diverse and admixed ancestry samples is provided.

Alcohol use and alcohol use disorder differ in their genetic relationships with PTSD: A genomic structural equation modelling approach

PURPOSE

Posttraumatic Stress Disorder (PTSD) is associated with increased alcohol use and alcohol use disorder (AUD), which are all moderately heritable. Studies suggest the genetic association between PTSD and alcohol use differs from that of PTSD and AUD, but further analysis is needed.

BASIC PROCEDURES

We used genomic Structural Equation Modeling (genomicSEM) to analyze summary statistics from large-scale genome-wide association studies (GWAS) of European Ancestry participants to investigate the genetic relationships between PTSD (both diagnosis and re-experiencing symptom severity) and a range of alcohol use and AUD phenotypes.

MAIN FINDINGS

When we differentiated genetic factors for alcohol use and AUD we observed improved model fit relative to models with all alcohol-related indicators loading onto a single factor. The genetic correlations (rG) of PTSD were quite discrepant for the alcohol use and AUD factors. This was true when modeled as a three-correlated-factor model (PTSD-AUD rG:.36, p < .001; PTSD-alcohol use rG: -0.17, p < .001) and as a Bifactor model, in which the common and unique portions of alcohol phenotypes were pulled out into an AUD-specific factor (rG with PTSD:.40, p < .001), AU-specific factor (rG with PTSD: -0.57, p < .001), and a common alcohol factor (rG with PTSD:.16, NS).

PRINCIPAL CONCLUSIONS

These results indicate the genetic architecture of alcohol use and AUD are differentially associated with PTSD. When the portions of variance unique to alcohol use and AUD are extracted, their genetic associations with PTSD vary substantially, suggesting different genetic architectures of alcohol phenotypes in people with PTSD.

Precollege and New-Onset College Interpersonal Trauma as Predictors of Baseline and Changes in Alcohol Use Disorder Symptoms During College

College is a high-risk time for interpersonal trauma (IPT) exposure (e.g., physical or sexual abuse/assault), a potent form of trauma exposure. College is also a high-risk time for alcohol misuse, as use begins and increases in adolescence and peaks in the early/mid-20s. In addition, although IPT is associated with alcohol misuse, less clear is whether distal (prior to college) or proximal (during college) IPT impacts alcohol use disorder (AUD) symptoms at the beginning of college and/or changes in symptoms during college. Data were collected from a large, longitudinal study of college students, attending a large public university in the southeast, who had reported lifetime IPT as well as lifetime alcohol use. Participants in the current study were 18.5 years old (SD = 0.46), primarily female (67.2%), and of diverse racial backgrounds (e.g., 53.4% White, 18.5% Black, 12.7% Asian, 15.4% Other). Latent change score analyses were employed to test the impact of IPT prior to college and IPT during college on initial levels of, and changes in, AUD symptoms during college. Those who experienced an IPT prior to college reported more AUD symptoms at the beginning of college and less changes in AUD symptoms during the first year of college. Those who experienced an IPT in the first 2 and last 2 years of college reported greater increases in symptoms in the first 2 and last 2 years of college, respectively. Findings suggest that prevention and intervention efforts for those who experience an IPT prior to or during college may be useful in reducing AUD symptoms during that time period.

Potential causal effect of posttraumatic stress disorder on alcohol use disorder and alcohol consumption in individuals of European descent: A Mendelian Randomization Study

BACKGROUND

Posttraumatic stress disorder (PTSD) often co-occurs with alcohol consumption (AC) and alcohol use disorder (AUD). However, it is unknown whether the same etiologic influences that underlie PTSD co-occurring with AUD are those that underlie PTSD and AC individually.

METHODS

This study used large-scale genome-wide association study (GWAS) data to test whether PTSD and drinks per week [DPW]/AUD are causally related to one another, and, if so, whether PTSD precedes DPW/AUD and/or vice versa. We used Mendelian Randomization methods to analyze European ancestry GWAS summary statistics from the Psychiatric Genomics Consortium (PGC; PTSD), GWAS & Sequencing Consortium of Alcohol and Nicotine Use (GSCAN; DPW), and the Million Veteran Program (MVP; AUD).

RESULTS

PTSD exerted a potentially causal effect on AUD (β = 0.039, SE = 0.014, p = 0.005), but not on DPW (β = 0.002, SE = 0.003, p = 0.414). Additionally, neither DPW (β = 0.019, SE = 0.041, p = 0.637) nor AUD (β = 8.87 × 10^-4 , SE = 0.001, p = 0.441) exerted a causal effect on PTSD.

CONCLUSIONS

These findings are consistent with the self-medication model, in which individuals misuse alcohol to cope with aversive trauma-related symptoms. These findings extend latent analysis and molecular findings of shared and correlated risk between PTSD and alcohol phenotypes. Given the health behaviors associated with these phenotypes, these findings are important in that they suggest groups to prioritize for prevention efforts. Further, they provide a rationale for future preclinical and clinical studies examining the biological mechanisms by which PTSD may impact AUD.

A behavioral genetic investigation of conceptualizations of resilience in a female twin sample

BACKGROUND

Great variability exists in response to stressful or traumatic events, leading to an interest in the construct of resilience as a trait and an outcome. The etiologic sources of variability across differing conceptualizations of resilience are poorly understood.

METHODS

Using behavioral genetic methods in a sample of 2,056 female twins, the present study sought to (a) examine the etiologic sources of a trait-based self-report measure of perceived resilience (PR), (b) determine the genetic and environmental overlap with an outcome-based measure of resilience, as defined by the absence of psychiatric symptoms after stressful life events, previously used by our research team (discrepancy-based psychiatric resilience [DBPR]), and (c) determine the etiologic overlap of these two resilience measures with major depressive disorder (MDD).

RESULTS

PR was modestly (11%) heritable. A moderate degree of genetic overlap (39%) and a nominal amount of environmental overlap (3%) were found between the two alternative measures of resilience. Genetic factors that influence PR accounted for 3% of MDD heritability, whereas 31% of MDD heritability was due to DBPR genetic factors.

CONCLUSIONS

Findings of a higher genetic correlation between the outcome-based resilience measure and MDD compared to the trait-based measure and MDD suggest gene-finding efforts may benefit from considering the multifaceted nature of resilience and that resilience is best understood as both a phenotypically and genetically heterogeneous construct.

The Nomological Network of a Behavioral Distress Tolerance Task in Veterans

There is a relative lack of research on distress tolerance (DT) in veteran samples. The aims of the study were to (a) evaluate convergent and discriminant validity of a behavioral measure of DT compared to theoretically similar (i.e., self-report DT, negative urgency) and dissimilar (i.e., risk-taking) constructs and (b) evaluate the concurrent validity of DT in relation to posttraumatic stress disorder (PTSD) and depressive symptoms in a veteran sample. A sample of U.S. veterans who served after the September 11, 2001 terror attacks (N = 306, 89.9% male; M age 30.2 years, SD = 4.5, range: 21-40 years) completed self-report and behavioral measures of DT, risk-taking, impulsivity, and depressive symptoms, and completed a clinical interview for PTSD. Results of a multitrait-multimethod matrix found significant yet minimal shared variance, r2 = .01-.03, ps = .002-.055, between the self-report and behavioral measures of DT. We used a series of multiple regressions to examine the relative contribution of the behavioral and self-report DT measures in the prediction of PTSD and depressive symptoms. Self-reported, but not behavioral, DT accounted for unique variance in PTSD, r2 = .12, p < .001, and depressive symptoms, r2 = .23, p < .001. Participants with PTSD or higher scores on measures of depression were more likely to report greater increases in frustration and irritability after completing the behavioral task. Results indicate that DT is not a unidimensional construct and must be considered in the context of specific emotions (e.g., tolerance of irritability vs. fear) and contexts (e.g., behavioral, affective).

Moderation of improvement in self-efficacy following group psychotherapy for PTSD

Posttraumatic stress disorder (PTSD) is a primary mental health concern of veterans. In clinical settings, efforts to improve broad facets beyond symptom amelioration and consideration of moderators of treatment effectiveness in this population are needed for continued improvement in care. General self-efficacy (GSE) has been indicated as a useful treatment target because of its association with positive outcomes such as increased positive health behaviors. Both race and educational attainment represent potential moderators of treatment response that are relevant for a veteran PTSD population. This study aimed to determine whether a PTSD Recovery Group Therapy Program resulted in improvement in GSE and whether racial and educational differences moderated GSE outcomes. Archival data were examined from male veterans (N = 450) receiving mental health services at a Veterans Affairs medical center using multilevel modeling to examine change in GSE over the course of treatment as well as moderation of change in GSE as a function of race and educational attainment. After completion of group therapy, results indicated there was significant improvement in GSE, with significantly different improvement based on education. Higher levels of education were associated with greater increases in GSE after treatment. Improvement in GSE did not differ by participant race. In clinical settings, efforts to increase GSE and attending to moderators such as educational attainment may be useful for improving PTSD treatment approaches. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Clinical Correlates of Carbon Dioxide Hypersensitivity in Children

OBJECTIVE

Hypersensitivity to carbon dioxide (CO₂)-enriched air may be a promising risk marker for anxiety disorders. Among adult and adolescent samples, heterogeneity in distress response to the CO₂ challenge task indexes 3 underlying classes of individuals, which distinguish between sustained and acute threat response as markers for internalizing disorders, broadly, and anxiety disorders, specifically. The present study examines latent classes in children's response to the CO₂ challenge task to clarify the association of CO₂ hypersensitivity with anxiety and internalizing symptomatology in childhood.

METHOD

Healthy children from a community twin sample (N = 538; age 9-13 years) rated anxious distress every 2 minutes while breathing air enriched to 7.5% CO₂ for 8 minutes. Latent growth mixture modeling evaluated potential classes of individuals with characteristic trajectories of distress during the task to clarify the association with internalizing disorder symptoms and related traits (e.g., anxiety sensitivity, irritability).

RESULTS

Although all participants reported increased distress during the task, interindividual heterogeneity in distress indexed 3 underlying classes: a consistently low class ("low"), a consistently high class ("high"), and participants who demonstrated markedly increased acute distress ("acute"). Compared to the low class, the high class reported greater internalizing psychopathology, whereas membership in the acute class was associated with experiencing a panic-like event during the task.

CONCLUSION

As in older individuals, 3 distinct trajectories emerged to capture interindividual heterogeneity in children's distress during the CO₂ challenge task. These classes were distinguished by clinical validators that reinforce the association of CO₂ hypersensitivity and internalizing disorder phenotypes in children.

Clinical characteristics of latent classes of CO2 hypersensitivity in adolescents and young adults

Although breathing CO₂-enriched air reliably increases anxiety, there is debate concerning the nature and specificity of CO₂ hypersensitivity to panic risk and panic disorder versus anxiety disorders and related traits broadly, particularly among adolescents and emerging adults. The present study sought to clarify the association of CO₂ hypersensitivity with internalizing conditions and symptoms among adolescents and young adults. Participants (N = 628) self-reported anxiety levels every 2 min while breathing air enriched to 7.5% CO₂ for 8 min. Growth mixture models were used to examine the structure of anxiety trajectories during the task and the association of each trajectory with dimensional and diagnostic assessments of internalizing disorders. Three distinct trajectories emerged: overall low (low), overall high (high), and acutely increased anxiety (acute). Compared to the low class, the acute class reported elevated neuroticism, anxiety sensitivity, and stress whereas the high class reported elevated anxiety symptoms, depression symptoms, neuroticism, anxiety sensitivity, and increased likelihood of an anxiety disorder diagnosis. Moreover, the acute and high classes reported experiencing a panic-like event at a higher rate than the low class while participants in the high class terminated the task prematurely at a higher rate. The present study clarifies the nature of response to CO₂ challenge. Three distinct response profiles emerged, which clarifies the manifestation of CO₂ hypersensitivity in anxiety disorders with strong, though not unique, associations with panic-relevant traits.

Relationships between GAT1 and PTSD, Depression, and Substance Use Disorder

Post-traumatic stress disorder (PTSD), Major Depressive Disorder (MDD), and Substance Use Disorder (SUD) have large public health impacts. Therefore, researchers have attempted to identify those at greatest risk for these phenotypes. PTSD, MDD, and SUD are in part genetically influenced. Additionally, genes in the glutamate and gamma-aminobutyric acid (GABA) system are implicated in the encoding of emotional and fear memories, and thus may impact these phenotypes. The current study examined the associations of single nucleotide polymorphisms in GAT1 individually, and at the gene level, using a principal components (PC) approach, with PTSD, PTSD comorbid with MDD, and PTSD comorbid with SUD in 486 combat-exposed veterans.  Findings indicate that several GAT1 SNPs, as well as one of the GAT1 PCs, was associated with PTSD, with and without MDD and SUD comorbidity. The present study findings provide initial insights into one pathway by which shared genetic risk influences PTSD-MDD and PTSD-SUD comorbidities, and thus identify a high-risk group (based on genotype) on whom prevention and intervention efforts should be focused.

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.

A population-based study of help seeking and self-medication among trauma-exposed individuals

Epidemiologic studies of trauma highlight the imbalance between prevalence of psychiatric diagnoses and help seeking. We investigated prevalence and correlates of help seeking and self-medication in Norwegian adults with trauma history with a focus on common posttrauma outcomes of posttraumatic stress disorder (PTSD) and substance use disorders (alcohol or drug). Participants reporting at least 1 PTSD symptom (n = 307) were asked if they consulted with a doctor/another professional (help seeking) or used drugs/alcohol (self-medication) for trauma-related problems. PTSD, alcohol abuse or dependence (AUD), and drug use or dependence (DUD) were assessed via structured diagnostic interviews. Help seeking and self-medication were endorsed by 37.4% and 10.4% of the sample, respectively. As compared to the full sample, help seeking was endorsed at a greater rate in individuals with PTSD (χ2 = 8.59, p = .005) and at a lower rate in those with AUD (χ2 = 7.34, p < .004). Self-medication was more likely to be endorsed by individuals with PTSD than without PTSD (χ2 = 25.68, p < .001). In regression analyses, PTSD was associated with increased likelihood of self-medication (odds ratio [OR] = 4.56) and help seeking (OR = 2.29), while AUD was associated with decreased likelihood of help-seeking (OR = .29). When self-medication was included as a predictor, PTSD was no longer associated with help seeking, although AUD remained inversely associated. PTSD and AUDs have a nuanced relationship with formal help seeking as well as the use of substances to cope. Trauma-exposed individuals are likely engaging in adaptive and maladaptive coping strategies, the latter of which may be compounding distress. (PsycINFO Database Record

Potentially Traumatic Events, Posttraumatic Stress Disorder, and Depression among Adults in Puerto Rico

The aims of the current study were to examine the prevalence of potentially traumatic events (PTEs), posttraumatic stress disorder (PTSD; data available in males only), and depressive symptoms in a Puerto Rican sample of 678 adult caretakers (50% female) of twins participating in the Puerto Rican Infant Twin Study. The World Health Organization Composite International Diagnostic Interview version 3.0 (CIDI 3.0) was utilized to assess rates of PTEs, PTSD, and depression among male participants while an abbreviated version of the CIDI 3.0 and the Mood and Feelings Questionnaire were administered to females to assess PTEs and depressive symptoms. Significantly more males than females reported exposure to a PTE (76.6% vs. 44.2%, χ(2) = 64.44, p < 0.001). In males, endorsement of multiple PTEs was associated with increased level of PTSD symptomatology (β = 0.33, p < 0.001). With regard to depression, a similar dose-response relationship was found in both males and females, with depressive symptoms increasing as number of PTEs increased (βs = 0.15, 0.16, ps < 0.05). Exposure to an attack with a weapon was significantly associated with increased depression symptoms in both males and females (βs = 0.24, 0.20, ps < 0.01, respectively). These findings highlight the need for identification of putative risk and resilience factors among PTE-exposed individuals in Puerto Rico.

Variation in SLC1A1 is related to combat-related posttraumatic stress disorder

Candidate gene studies have yet to investigate the glutamate system, the primary excitatory neurotransmitter of the HPA-axis related to PTSD risk. We investigated 13 SNPs in the glutamate transporter gene (SLC1A1) in relation to PTSD among combat-exposed veterans. Participants (n=418) completed a diagnostic interview and provided a blood sample for DNA isolation and genotyping. A subset of participants (n=391) had severity and combat exposure data available. In the primary logistic regression gender and rs10739062 were significant predictors of PTSD diagnosis (OR=0.50; OR=1.43). In the linear regression analysis, combat exposure was the only significant predictor (β=0.16) of severity. A computed genetic risk sum score was significant in relation to PTSD diagnosis (OR=1.15) and severity scores (β=0.14) above and beyond the effects of combat exposure. This study provides preliminary support for the relationship of glutamate transporter polymorphisms to PTSD risk and the need for further genetic studies within this system.