Diminished vagal activity and blunted diurnal variation of heart rate dynamics in posttraumatic stress disorder

Heart rate variability characteristics in a large group of active-duty marines and relationship to posttraumatic stress

OBJECTIVE

Heart rate variability (HRV), thought to reflect autonomic nervous system function, is lowered under conditions such as posttraumatic stress disorder (PTSD). The potential confounding effects of traumatic brain injury (TBI) and depression in the relationship between HRV and PTSD have not been elucidated in a large cohort of military service members. Here we describe HRV associations with stress disorder symptoms in a large study of Marines while accounting for well-known covariates of HRV and PTSD including TBI and depression.

METHODS

Four battalions of male active-duty Marines (n = 2430) were assessed 1 to 2 months before a combat deployment. HRV was measured during a 5-minute rest. Depression and PTSD were assessed using the Beck Depression Inventory and Clinician-Administered PTSD Scale, respectively.

RESULTS

When adjusting for covariates, including TBI, regression analyses showed that lower levels of high-frequency HRV were associated with a diagnosis of PTSD (β = -0.20, p = .035). Depression and PTSD severity were correlated (r = 0.49, p < .001); however, participants with PTSD but relatively low depression scores exhibited reduced high frequency compared with controls (p = .012). Marines with deployment experience (n = 1254) had lower HRV than did those with no experience (p = .033).

CONCLUSIONS

This cross-sectional analysis of a large cohort supports associations between PTSD and reduced HRV when accounting for TBI and depression symptoms. Future postdeployment assessments will be used to determine whether predeployment HRV can predict vulnerability and resilience to the serious psychological and physiological consequences of combat exposure.

The 5-HTTLPR genotype modulates heart rate variability and its adjustment by pharmacological panic challenge in healthy men

Abnormal serotonin transporter (5-HTT) function and autonomic nervous system (ANS) dysregulation has been proposed in panic disorder. However, in contrast to hypothalamo-pituitary-adrenocortical (HPA) functioning, ANS reactivity during panic response has yet not been investigated in humans with respect to the 5-HTT genotype. The present study assessed the influence of challenging by cholecystokinin tetrapeptide (CCK-4) on heart rate variability (HRV) measures, to monitor autonomic reactivity and its relationship to 5-HTT-linked polymorphic region (5-HTTLPR) genotypes. We hypothesized substantial effects of the 5-HTTLPR genotype on autonomic reactivity. We studied 30 healthy young men, 15 of each with the long/long (l/l) or short/short (s/s) genotype for the 5-HTTLPR. All participants received an intravenous application of 50 μg CCK-4. HRV measures were assessed in both groups at baseline and immediately after CCK-4 application. Our results indicated lower parasympathetic activity in s/s carriers during baseline, time and frequency domain measures. CCK-4 application significantly enhanced the sympathetic tone in both groups, leading to diminished group differences. A significant treatment by genotype effect indicated reduced autonomic reactivity to CCK-4 challenge in the s/s compared to l/l carriers. Our findings show enhanced sympathetic and/or diminished cardiac vagal activity under basal conditions and blunted autonomic reactivity in s/s vs. l/l carriers. Our study provides novel data supporting claims that the s/s genotype represents a genetic vulnerability factor associated with inadequate hyporeactivity to stress and extends current knowledge on the impact of the central serotonergic activity on the sympathoadrenal pathway.

Psychophysiology in the study of psychological trauma: where are we now and where do we need to be?

Posttraumatic stress disorder (PTSD) is a major public health concern, which has been seeing increased recent attention partly due to the wars in Iraq and Afghanistan. Historically, research attempting to understand the etiology and treatment of PTSD has made frequent use of psychophysiological measures of arousal as they provide a number of advantages in providing objective, non-self-report outcomes that are closely related to proposed neurobiological mechanisms and provide opportunity for cross-species translation. Further, the ongoing shift in classification of psychiatric illness based on symptom clusters to specific biological, physiological, and behavioral constructs, as outlined in the US National Institute of Mental Health (NIMH) Research Domain Criteria project (RDoC), promises that psychophysiological research will continue to play a prominent role in research on trauma-related illnesses. This review focuses on the current state of the knowledge regarding psychophysiological measures and PTSD with a focus on physiological markers associated with current PTSD symptoms, as well as markers of constructs thought to be relevant to PTSD symptomatology (safety signal learning, fear extinction), and psychophysiological markers of risk for developing PTSD following trauma. Future directions and issues for the psychophysiological study of trauma including traumatic brain injury (TBI), treatment outcome studies, and new wearable physiological monitoring technologies are also discussed.

Anxiety Disorders are Associated with Reduced Heart Rate Variability: A Meta-Analysis

BACKGROUND

Anxiety disorders increase risk of future cardiovascular disease (CVD) and mortality, even after controlling for confounds including smoking, lifestyle, and socioeconomic status, and irrespective of a history of medical disorders. While impaired vagal function, indicated by reductions in heart rate variability (HRV), may be one mechanism linking anxiety disorders to CVD, prior studies have reported inconsistent findings highlighting the need for meta-analysis.

METHOD

Studies comparing resting-state HRV recordings in patients with an anxiety disorder as a primary diagnosis and healthy controls were considered for meta-analysis.

RESULTS

Meta-analyses were based on 36 articles, including 2086 patients with an anxiety disorder and 2294 controls. Overall, anxiety disorders were characterized by lower HRV [high frequency (HF): Hedges' g = -0.29. 95% CI: -0.41 to -0.17, p < 0.001; time domain: Hedges' g = -0.45, 95% CI: -0.57 to -0.33, p < 0.001] than controls. Panic disorder (n = 447), post-traumatic stress disorder (n = 192), generalized anxiety disorder (n = 68), and social anxiety disorder (n = 90), but not obsessive-compulsive disorder (n = 40), displayed reductions in HF HRV relative to controls (all ps < 0.001).

CONCLUSION

Anxiety disorders are associated with reduced HRV, findings associated with a small-to-moderate effect size. Findings have important implications for future physical health and well-being of patients, highlighting a need for comprehensive cardiovascular risk reduction.

Munc18-1 haploinsufficiency results in enhanced anxiety-like behavior as determined by heart rate responses in mice

Heterozygous (HZ) missense mutations in the gene encoding syntaxin binding protein 1 (Stxbp1 or Munc18-1), a presynaptic protein essential for neurotransmitter release, causes early infantile epileptic encephalopathy, abnormal brain structure and mental retardation in humans. Here we investigated whether the mouse model mimics symptoms of the human phenotype. The effects of the deletion of munc18-1 were studied in HZ and wild-type (WT) mice based on heart rate (HR) and its variability (HRV) as independent measures to expand previous behavioral results of enhanced anxiety and impaired emotional learning suggesting mild cognitive impairments. HR responses were assessed during novelty exposure, during the expression and extinction of conditioned tone-dependent fear and during the diurnal phase. Novelty exposure yielded no differences in activity patterns between the two genotypes, while maximum HR differed significantly (WT: 770 bpm; HZ: 790 bpm). Retention tests after both auditory delay and trace fear conditioning showed a delayed extinction of the conditioned HR response in HZ mice compared to WT mice. Since the HR versus HRV correlation and HR dynamics assessed by nonlinear methods revealed similar function in HZ and WT mice, the higher HR responses of munc18-1 HZ mice to different emotional challenges cannot be attributed to differences in autonomic nervous system function. Thus, in contrast to the adverse consequences of deletion of a single allele of munc18-1 in humans, C57BL/6J mice show enhanced anxiety responses based on HR adjustments that extend previous results on the behavioral level without support of cognitive impairment, epileptic seizures and autonomic dysregulation.