Resting respiratory sinus arrhythmia in suicide attempters

A Swedish population-based study to evaluate the usefulness of resting heart rate in the prediction of suicidal behavior among males

INTRODUCTION

Resting heart rate has been distinctly related to both internalizing (high pulse) and externalizing (low pulse) disorders. We aimed to explore the associations between resting heart rate and suicidal behavior (nonfatal suicide attempt [SA] and suicide death [SD]) and evaluate if such associations exist beyond the effects of internalizing/externalizing symptomatology.

METHOD

We used Cox proportional hazards models to evaluate the associations between resting heart rate (age 19) and later SA/SD in 357,290 Swedish men. Models were controlled for internalizing disorders, externalizing disorders, and resilience (the ability to deal with adversity). Co-relative analysis (comparing pairs of different genetic relatedness) was used to control for unmeasured family confounders and improve causal inference.

RESULTS

In baseline models, low resting heart rate was associated with SA (HR = 0.96; 95% CI: 0.95,0.98) and high resting heart rate with SD (HR = 1.04; 95% CI: 1.002,1.07). The association with SA remained after adjustment for all confounders (HR = 0.98). However, the association with SD did not persist after controlling for covariates. Co-relative analysis did not support causal associations.

CONCLUSIONS

Our findings raise interesting etiological questions for the understanding of suicidal behaviors but do not support the usefulness of resting heart rate in suicide prediction.

From Social Stress and Isolation to Autonomic Nervous System Dysregulation in Suicidal Behavior

PURPOSE OF REVIEW

In this narrative review we wanted to describe the relationship of autonomic nervous system activity with social environment and suicidal spectrum behaviors.

RECENT FINDINGS

Patients with suicidal ideation/suicide attempt have higher sympathetic nervous system (SNS) and lower parasympathetic nervous system (PNS) activity in resting conditions and during acute stress tasks compared with patients without suicidal ideation/suicide attempt. Death by suicide and violent suicide attempt also are related to SNS hyperactivation. Similarly, a SNS/PNS imbalance has been observed in people with childhood trauma, stressful life events or feelings of loneliness and isolation. Social support seems to increase PNS control and resilience. Due to the importance of the social context and stressful life events in suicidal behavior, SNS/PNS imbalance could act as a mediator in this relationship and be a source of relevant biomarkers. Childhood trauma and stressful life events may impair the autonomic nervous system response in suicidal patients. Loneliness, isolation and social support may act as moderators in acute stress situations.

Neuroimaging and Biosample Collection in the Toronto Adolescent and Youth Cohort Study: Rationale, Methods, and Early Data

BACKGROUND

The Toronto Adolescent and Youth (TAY) Cohort Study will characterize the neurobiological trajectories of psychosis spectrum symptoms, functioning, and suicidality (i.e., suicidal thoughts and behaviors) in youth seeking mental health care. Here, we present the neuroimaging and biosample component of the protocol. We also present feasibility and quality control metrics for the baseline sample collected thus far.

METHODS

The current study includes youths (ages 11-24 years) who were referred to child and youth mental health services within a large tertiary care center in Toronto, Ontario, Canada, with target recruitment of 1500 participants. Participants were offered the opportunity to provide any or all of the following: 1) 1-hour magnetic resonance imaging (MRI) scan (electroencephalography if ineligible for or declined MRI), 2) blood sample for genomic and proteomic data (or saliva if blood collection was declined or not feasible) and urine sample, and 3) heart rate recording to assess respiratory sinus arrhythmia.

RESULTS

Of the first 417 participants who consented to participate between May 4, 2021, and February 2, 2023, 412 agreed to participate in the imaging and biosample protocol. Of these, 334 completed imaging, 341 provided a biosample, 338 completed respiratory sinus arrhythmia, and 316 completed all 3. Following quality control, data usability was high (MRI: T1-weighted 99%, diffusion-weighted imaging 99%, arterial spin labeling 90%, resting-state functional MRI 95%, task functional MRI 90%; electroencephalography: 83%; respiratory sinus arrhythmia: 99%).

CONCLUSIONS

The high consent rates, good completion rates, and high data usability reported here demonstrate the feasibility of collecting and using brain imaging and biosamples in a large clinical cohort of youths seeking mental health care.

A History of Suicide Attempt Is Associated with Increased Sympathetic Activation in Bipolar Disorder

OBJECTIVE

Suicide risk in bipolar disorder (BD) is estimated to be up to 20 times higher than in the general population. While there is a large body of evidence suggesting that increased sympathetic activation is associated with disease and death, there is a paucity of research on the role of autonomic nervous system (ANS) dysfunction in patients with BD who have attempted suicide.

METHODS

Fifty-three participants with BD used a wearable device to assess the association between history of suicide attempt, current suicidal ideation, and ANS dysfunction, including measures of heart rate variability (HRV) and respiratory rate. Data were analyzed in a series of unadjusted and adjusted bivariate models of association controlling for relevant variables.

RESULTS

A history of suicide attempts was significantly associated with an increase in respiratory rate (p < 0.01). These results remained significant after adjusting for age, BMI, and current mood state. There was no association between current suicidal ideation and heart rate or respiratory rate. In the frequency domain, HRV parameters suggest reduced parasympathetic (i.e., vagal) activity in participants with a history of suicide attempts and in those with current suicidality, suggesting changes in sympathicovagal balance in BD.

CONCLUSIONS

Our results suggest that changes in the ANS in patients with BD and a history of suicide attempt are not restricted to pure vagally mediated HRV parameters, but rather signal a general ANS dysregulation. This ANS imbalance may be contributing to illness burden and cardiovascular disease. Further research on the relationship between ANS and suicidality in BD is needed.

Differences in the distribution of triggers among resting state networks in patients with juvenile myoclonic epilepsy explained by network analysis

Background

Juvenile myoclonus epilepsy (JME) is an idiopathic generalized epilepsy syndrome. Functional connectivity studies based on graph theory have demonstrated changes in functional connectivity among different brain regions in patients with JME and healthy controls. However, previous studies have not been able to clarify why visual stimulation or increased cognitive load induces epilepsy symptoms in only some patients with JME.

Methods

This study constructed a small-world network for the visualization of functional connectivity of brain regions in patients with JME, based on system mapping. We used the node reduction method repeatedly to identify the core nodes of the resting brain network of patients with JME. Thereafter, a functional connectivity network of the core brain regions in patients with JME was established, and it was analyzed manually with white matter tracks restriction to explain the differences in symptom distribution in patients with JME.

Results

Patients with JME had 21 different functional connections in their resting state, and no significant differences in their distribution were noted. The thalamus, cerebellum, basal ganglia, supplementary motor area, visual cortex, and prefrontal lobe were the core brain regions that comprised the functional connectivity network in patients with JME during their resting state. The betweenness centrality of the prefrontal lobe and the visual cortex in the core functional connectivity network of patients with JME was lower than that of the other brain regions.

Conclusion

The functional connectivity and node importance of brain regions of patients with JME changed dynamically in the resting state. Abnormal discharges originating from the thalamus, cerebellum, basal ganglia, supplementary motor area, visual cortex, and prefrontal cortex are most likely to lead to seizures in patients with JME. Further, the low average value of betweenness centrality of the prefrontal and visual cortices explains why visual stimulation or increased cognitive load can induce epileptic symptoms in only some patients with JME.

Respiratory sinus arrhythmia, negative social interactions, and fluctuations in unmet interpersonal needs: A daily diary study

INTRODUCTION

This study examined daily fluctuations in the unmet interpersonal needs of thwarted belongingness and perceived burdensomeness in response to daily negative social interactions, as well as the moderating role of respiratory sinus arrhythmia (RSA) across adolescents at lower and higher risk for suicidal ideation.

METHODS

Fifty five adolescents with major depressive disorder (MDD, i.e., higher-risk group) and without MDD (i.e., lower-risk group) completed measures of resting RSA, and daily measures of negative social interactions, perceived burdensomeness, and loneliness, as a proxy for thwarted belongingness, for 10 consecutive days. Within-person analyses examined the association between daily negative social interactions and unmet interpersonal needs, and the moderating roles of RSA and higher-risk group status. Between-person analyses also examined the association between RSA and unmet interpersonal needs across groups.

RESULTS

At the within-person level, participants reported more unmet interpersonal needs on days when they reported more negative social interactions. At the between-person level, higher RSA was associated with decreased loneliness in both groups, and decreased burdensomeness among the higher-risk group.

CONCLUSIONS

Negative social interactions are associated with daily unmet interpersonal needs. Higher RSA may serve as a protective factor mitigating risk for unmet interpersonal needs, particularly burdensomeness, among adolescents at higher risk for suicidal ideation.

An RDoC-based approach to adolescent self-injurious thoughts and behaviors: The interactive role of social affiliation and cardiac arousal

Recent theoretical models have posited that increases in self-injurious thoughts and behaviors (SITBs) during adolescence may be linked to failures in biological stress regulation in contexts of social stress. However, there is a lack of data examining this hypothesis during the transition to adolescence, a sensitive period of development characterized by changes across socioaffective and psychophysiological domains. Building on principles from developmental psychopathology and the RDoC framework, the present study used a longitudinal design in a sample of 147 adolescents to test whether interactions among experiences of social (i.e., parent and peer) conflict and cardiac arousal (i.e., resting heart rate) predicted adolescents' engagement in SITBs (i.e., nonsuicidal self-injury, NSSI; and suicidal ideation; SI) across 1-year follow-up. Prospective analyses revealed that adolescents experiencing a combination of greater peer, but not family, conflict and higher cardiac arousal at baseline showed significant longitudinal increases in NSSI. In contrast, social conflict did not interact with cardiac arousal to predict future SI. Findings indicate that greater peer-related interpersonal stress in adolescents may increase risk for future NSSI among youth with physiological vulnerabilities (i.e., higher resting heart rate) that may be markers of maladaptive stress responses. Future research should examine these processes at finer timescales to elucidate whether these factors are proximal predictors of within-day SITBs.

A recent suicide attempt and the heartbeat: Electrophysiological findings from a trans-diagnostic cohort of patients and healthy controls

Suicidal behavior is influenced by a multitude of factors, making prediction and prevention of suicide attempts (SA) a challenge. A useful tool to uncover underlying pathophysiology or propose new therapy approaches are biomarkers, especially within the context of point-of-care tests. Heart rate variability (HRV) is a well-established biomarker of mental health, and measures the activity of the sympathetic and parasympathetic nervous system (PNS). Previous studies reported a correlation between lower PNS activity and suicidality. However, most studies involved participants from a healthy population, patients without history of suicide attempts, or patients with a single diagnosis. 52 in-patients with a recent suicide attempt (<6 months), and 43 controls without history of SA or psychiatric diagnoses confirmed study participation. The included patients age ranged between 18 and 65 years, 65% had psychiatric comorbidities. Patients with dementia, cognitive impairments, acute psychosis, chronic non suicidal self-harming behavior, or current electroconvulsive therapy were excluded. A 15-min resting state electrocardiography was recorded with two bipolar electrodes attached to the right and left insides of the wrists. The multiple regression analyses showed lower parasympathetic, and higher sympathetic activity in patients compared to controls. Partial correlation found a positive trend result between self-reported suicidality and the very low frequency band. ROC curve analysis revealed an acceptable to excellent clinical accuracy of HRV parameters. Therefore, HRV parameters could be reliable discriminative biomarkers between in-patients with a recent SA and healthy controls. One limitation is the lack of a control group consisting of in-patients without life-time suicidal ideation or attempts.

Analysis of Early Warning Diagnostic Indexes and Influencing Factors of Anxiety and Depression in Patients with Arrhythmia

Objective

Arrhythmia patients complicated with psychological problems are very common in clinics. The imbalance of autonomic nervous regulation of the heart caused by anxiety and depression will further promote the occurrence and development of arrhythmia. For nonorganic heart disease, β receptor blockers combined with antianxiety drugs have a good effect. Therefore, it is necessary to analyze the influencing factors of anxiety and depression in patients with arrhythmias.

Methods

We included 150 patients with arrhythmia and divided them into observation groups (80 patients with anxiety and depression) and control groups (70 patients without anxiety and depression). All patients were monitored by Holter, and the detection of arrhythmia was compared between the two groups. We took the general situation and quality of life of the investigated patients as independent variables and the anxiety and depression status of the patients as dependent variables.

Results

The detection rates of atrioventricular premature beats, ventricular premature beats, atrial fibrillation, short bursts of atrial tachycardia, and atrioventricular block in the observation group were all higher than those in the control group by dynamic electrocardiogram. Multivariate logistic stepwise regression analysis showed that age, years of education, obsessive-compulsive score, somatization score and alcohol consumption were the main influencing factors for anxiety and depression.

Conclusions

The detection rate of arrhythmia in patients with anxiety/depression status was higher than in those without abnormal psychophylaxis. We should need to pay close attention to the risk factors of age, education years, obsessive-compulsive score, somatization score, and alcohol consumption, so as to prevent and timely detect anxiety and depression symptoms in patients with arrhythmias.

Associations of three major physiological stress systems with suicidal ideation and suicide attempts in patients with a depressive and/or anxiety disorder

BACKGROUND

People with depressive and/or anxiety disorders are at increased risk of suicidal ideation and suicide attempts, but biological correlates signaling such risk remain unclear. Independent and cumulative dysregulations in physiological stress systems, in particular the hypothalamic-pituitaryadrenal axis (HPA-axis), immune-inflammatory system, and autonomous nervous system (ANS), may contribute to this risk. However, findings have either been heterogeneous or absent thus far.

METHODS

Associations between individual markers and cumulative indices of the HPA-axis (cortisol awakening response and evening cortisol), immune-inflammatory system (C-reactive protein, interleukin-6 (IL-6), and tumor necrosis factor-α), and the ANS (heart rate, respiratory sinus arrhythmia, and pre-ejection period) and the outcomes no suicide ideation with suicide attempt (SI-SA+), suicide ideation without suicide attempt (SI+SA-) and suicide ideation with suicide attempt (SI+SA+) were investigated in 1749 persons with depressive and/or anxiety disorders from the Netherlands Study of Depression and Anxiety (NESDA).

RESULTS

High levels of CRP and IL-6 were associated with SI-SA+ and SI+SA+ respectively when compared to non-suicidal patients after adjusting for confounders and multiple testing. Also, cumulative immune-inflammatory dysregulations were positively associated with SI+SA+, suggesting a dose-response effect. No significant associations were found between HPA-axis or ANS indicators and suicide-outcomes and between immune-inflammatory system markers or cumulative stress system dysregulations and SI+SA-.

CONCLUSION

Although stress system markers could not differentiate between SI+SA- and non-suicidal patients, findings indicate that dysregulations of individual and cumulative immune-inflammatory markers are associated with suicide attempts in depressive and/or anxiety patients. Thus, immune-inflammatory system dysregulation may be involved in the pathophysiology of suicidal behavior, supporting further examination of the effects of anti-inflammatory interventions on suicidality.

Associations between heart rate variability, peripheral inflammatory markers and major depressive disorder

BACKGROUND

Measures for the irregularity of the heartbeat, for example respiratory sinus arrhythmia, have been implicated as a measure for restorative functions of the vegetative nervous system.

METHODS

In the current observational study, we investigated 265 subjects, 70 of whom had a lifetime history of major depression, with a plethysmographic heartbeat monitor, blood sampling, as well as a range of psychiatric questionnaires.

RESULTS

Subjects with a history of MDE had significantly reduced respiratory sinus arrhythmia (RSA) as compared to never-depressed controls; in the whole sample, higher RSA went with lower anxiety/fear variables, especially in subscores related to cardiac symptoms as well as being afraid of dying. A reduced RSA was also associated with an increased concentration of cytokines (TNFa, IL1a, IL6, IFNg) and thyroid-stimulating hormone in the serum, pointing to a possible triangular relationship between immune system, vegetative nervous system, and emotional dysregulation.

LIMITATIONS

We used a plethysmographic device for the measurement of heartbeat instead of an electrocardiogram, and had a single time point only.

CONCLUSIONS

This data corroborate the idea that a disequilibrium of the vegetative nervous, especially if accompanied by a dysregulation system in immune function, can increase the risk for depression. Conversely, vagal stimulation and anti-inflammatory treatments may support the treatment with antidepressants.

The Physiologic and Emotional Effects of 360-Degree Video Simulation on Head-Mounted Display Versus In-Person Simulation: A Noninferiority, Randomized Controlled Trial

INTRODUCTION

A key simulation component is its capability to elicit physiological changes, improving recall. The primary aim was to determine whether parasympathetic responses to head-mounted display simulations (HMDs) were noninferior to in-person simulations. The secondary aims explored sympathetic and affective responses and learning effectiveness.

METHODS

The authors conducted a noninferiority trial. Hospital providers who did not use chronotropic medications, have motion sickness, or have seizures were included. The authors randomized participants to in-person or HMD simulation. Biometric sensors collected respiratory sinus arrhythmia and skin conductance levels to measure parasympathetic and sympathetic states at baseline, during, and after the simulation. Affect was measured using a schedule. The authors measured 3-month recall of learning points and used split-plot analysis of variance and Mann-Whitney U tests to analyze.

RESULTS

One hundred fifteen participants qualified, and the authors analyzed 56 in each group. Both groups experienced a significant change in mean respiratory sinus arrhythmia from baseline to during and from during to afterward. The difference of change between the groups from baseline to during was 0.134 (95% confidence interval = 0.142 to 0.410, P = 0.339). The difference of change from during the simulation to after was -0.060 (95% confidence interval = -0.337 to 0.217, P = 0.670). Noninferiority was not established for either period. Sympathetic arousal did not occur in either group. Noninferiority was not established for the changes in affect that were demonstrated. The mean scores of teaching effectiveness and achievement scores were not different.

CONCLUSIONS

Although a parasympathetic and affective response to the video simulation on an HMD did occur, it was not discernibly noninferior to in-person in this study.

Development of Autonomic Nervous System Assays as Point-of-Care Tests to Supplement Clinical Judgment in Risk Assessment for Suicidal Behavior: A Review

PURPOSE OF REVIEW

A biomarker point-of-care (POC) test that supplements the psychiatric interview and improves detection of patients at risk for suicide would be of value, and assays of autonomic nervous system (ANS) activity would satisfy the logistical requirements for a POC test. We performed a selective review of the available literature of ANS assays related to risk for suicide.

RECENT FINDINGS

We searched PubMed and Web of Science with the strategy: "suicide OR suicidal" AND "electrodermal OR heart rate variability OR pupillometry OR pupillography." The search produced 119 items, 21 of which provided original data regarding ANS methods and suicide. These 21 studies included 6 for electrodermal activity, 14 for heart rate variability, and 1 for the pupillary light reflex. The 21 papers showed associations between ANS assays and suicide risk in a direction suggesting underlying hyperarousal in patients at risk for suicide. ANS assays show promise for future development as POC tests to supplement clinical decision making in estimating risk for suicide.

Advances in Research on Adolescent Suicide and a High Priority Agenda for Future Research

Suicide is the second leading cause of death for adolescents in the United States, yet remarkably little is known regarding risk factors for suicidal thoughts and behaviors (STBs), relatively few federal grants and scientific publications focus on STBs, and few evidence-based approaches to prevent or treat STBs are available. This "decade in review" article discusses five domains of recent empirical findings that span biological, environmental, and contextual systems and can guide future research in this high priority area: (1) the role of the central nervous system; (2) physiological risk factors, including the peripheral nervous system; (3) proximal acute stress responses; (4) novel behavioral and psychological risk factors; and (5) broader societal factors impacting diverse populations and several additional nascent areas worthy of further investigation.

Heart Rate Variability and Its Ability to Detect Worsening Suicidality in Adolescents: A Pilot Trial of Wearable Technology

OBJECTIVE

Suicide is the 2nd leading cause of death in adolescence, and acute pediatric mental health emergency department (ED) visits have doubled in the past decade. The objective of this study was to evaluate physiologic parameters relationship to suicide severity.

METHODS

This was a prospective, observational study from April 2018 thru November 2019 in a tertiary care pediatric emergency department (ED) and inpatient pediatric psychiatric unit enrolling acutely suicidal adolescent patients. Patients wore a wrist device that used photoplethysmography for 7 days during their acute hospitalization to measure heart rate variability (HRV). During that time, Columbia Suicide Severity Scores (CSSRS) were assessed at 3 time points.

RESULTS

There was complete device data and follow-up for 51 patients. There was an increase in the high frequency (HF) component of HRV in patients that had a 25% or greater decrease in their CSSRS (mean difference 11.89 ms/ Hz ; p-value 0.005). Patients with a CSSRS≥15 on day of enrollment had a lower, although not statistically significant, HF component (mean difference -8.34 ms/ Hz; p-value 0.071).

CONCLUSION

We found an inverse correlation between parasympathetic activity measured through the HF component and suicidality in an acutely suicidal population of adolescents. Wearable technology may have the ability to improve outpatient monitoring for earlier detection and intervention.

Association of Resting Heart Rate and Heart Rate Variability With Proximal Suicidal Risk in Patients With Diverse Psychiatric Diagnoses

Objectively measurable biomarkers have not been applied for suicide risk prediction. Resting heart rate (HR) and heart rate variability (HRV) showed potential as trans-diagnostic markers associated with suicide. This study aimed to investigate the associations of resting HR and HRV on proximal suicide risk in patients with diverse psychiatric diagnoses. This chart review study used the medical records of psychiatric patients who visited the outpatient clinic at an academic tertiary hospital. A total of 1,461 patients with diverse psychiatric diagnoses was included in the analysis. Proximal suicide risk was measured using the Mini-International Neuropsychiatric Interview (MINI) suicidal score. Linear regression analyses with the MINI suicidal score as a dependent variable and binary logistic regression analyses with moderate-to-high suicide risk (MINI suicidal risk score ≥6) as a dependent variable were conducted to explore the effects of resting HR and HRV parameters on acute suicide risk after adjusting for age, sex, presence of major depressive disorder (MDD) and bipolar disorder (BD), severity of depression and anxiety severity. We found that 55 (34.6%) patients in the MDD group, 40 (41.7%) in the BD group and 36 (3.9%) in the others group reported moderate-to-high suicide risk. Linear regression analysis revealed that both resting HR and root-mean-square of successive difference (RMSSD) had significant associations with the MINI suicidal score (P = 0.037 with HR, P = 0.003 with RMSSD). In logistic regression, only RMSSD showed a significant association with moderate-to-high suicide risk (P = 0.098 with HR, P = 0.019 with RMSSD), which remained significant in subgroup analysis with patients who reported any suicide-related symptom (MINI suicidal score >0; n = 472; P = 0.017 with HR, P = 0.012 with RMSSD). Our study findings suggest the potential for resting HR and RMSSD as biomarkers for proximal suicide risk prediction. Further research with longitudinal evaluation is needed to confirm our study findings.

Objective measurement of sleep, heart rate, heart rate variability, and physical activity in suicidality: A systematic review

BACKGROUND

Emerging literature suggests that the arousal and regulatory systems as measured by sleep-wakefulness, heart rate (HR) and heart rate variability (HRV) may be powerful objective warning signs of suicidality. However, there is no systematic literature review examining the association between objective measurements of these variables with suicide and suicidal behavior.

METHODS

A web-based, systematic literature search using PubMed and EMBASE was conducted for articles that measured sleep-wakefulness and HR/HRV quantitatively in association with suicide. Search results were limited to human subjects and articles published in peer-reviewed journals in English. There were no restrictions for age, sex, settings and durations of measurements, types of mental illnesses, or comorbidity.

RESULTS

Twenty-three studies were included in the current systematic review. Across the studies, consistent patterns of disturbed sleep-wakefulness such as greater sleep onset latency and lower sleep efficiency were related to suicide. In addition, higher HR and lower variance of R-R intervals was an indicator of risk of suicide.

LIMITATIONS

Studies that used different equipment for sleep studies (i.e., polysomnography, electroencephalogram, actigraphy) were combined, and potential differences in their findings due to the different equipment were not considered.

CONCLUSIONS

Findings provide initial evidence for consistent patterns of sleep-wakefulness and HR/HRV possibly associated with suicidality; however, more studies are needed in order to identify the precise objective variables (e.g., sleep onset latency, high-frequency HRV), as well as time-varying patterns in these variables, that are related to acute suicide risk.

Autonomic correlates of lifetime suicidal thoughts and behaviors among adolescents with a history of depression

Suicidal thoughts and behaviors (STBs) have been associated with emotion dysregulation and atypical responses to affective and stressful stimuli. To investigate the psychophysiology involved, we measured changes in respiratory sinus arrhythmia (RSA) and cardiac pre-ejection period (PEP; indexing parasympathetic and sympathetic functioning, respectively) in response to stressful- and sadness-eliciting laboratory probes. Our sample included adolescents with a history of depression and STBs (n = 177), adolescents with a history of depression but no history of STBs (n = 47), and healthy controls (n = 175). The outcome of interest was the most severe form of clinician-rated STBs across the subject's lifetime. In partial support of our hypotheses, during the stressful task, adolescents with a history of depression and STBs did not evidence the RSA decrease that was exhibited by controls and displayed greater PEP shortening compared to ever-depressed adolescents with no lifetime STBs. No group differences were found in either RSA or PEP reactivity to the sadness-eliciting stimulus. As expected, severity of STBs was positively correlated with the extent of PEP shortening during the stressful task. The results suggest that adolescents with a history of depression and STBs experience blunted parasympathetic responses to stress along with compensatory efforts. Our findings contribute to a better understanding of STBs among youths and underscore that future studies should examine physiological risk factors for these psychopathological outcomes.

Adolescent Suicide as a Failure of Acute Stress-Response Systems

Suicide is the second leading cause of death worldwide for adolescents. Despite decades of research on correlates and risk factors for adolescent suicide, we know little about why suicidal ideation and behavior frequently emerge in adolescence and how to predict, and ultimately prevent, suicidal behavior among youths. In this review, we first discuss knowledge regarding correlates, risk factors, and theories of suicide. We then review why adolescence is a period of unique vulnerability, given changing biology and social network reorganization. Next, we present a conceptual model through which to interpret emerging findings in adolescent suicide research. We suggest that a promising area for future research is to examine adolescent suicide as a failure of biological responses to acute stress in the proximal moments of a suicidal crisis. After reviewing initial evidence for this conceptualization, we review future directions for studies on adolescent suicide.