Pupillary light reflex markers of suicide risk in a trans-diagnostic sample

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.

The impact of Alzheimer's disease risk factors on the pupillary light response

Alzheimer's disease (AD) is the leading cause of dementia, and its prevalence is increasing and is expected to continue to increase over the next few decades. Because of this, there is an urgent requirement to determine a way to diagnose the disease, and to target interventions to delay and ideally stop the onset of symptoms, specifically those impacting cognition and daily livelihood. The pupillary light response (PLR) is controlled by the sympathetic and parasympathetic branches of the autonomic nervous system, and impairments to the pupillary light response (PLR) have been related to AD. However, most of these studies that assess the PLR occur in patients who have already been diagnosed with AD, rather than those who are at a higher risk for the disease but without a diagnosis. Determining whether the PLR is similarly impaired in subjects before an AD diagnosis is made and before cognitive symptoms of the disease begin, is an important step before using the PLR as a diagnostic tool. Specifically, identifying whether the PLR is impaired in specific at-risk groups, considering both genetic and non-genetic risk factors, is imperative. It is possible that the PLR may be impaired in association with some risk factors but not others, potentially indicating different pathways to neurodegeneration that could be distinguished using PLR. In this work, we review the most common genetic and lifestyle-based risk factors for AD and identify established relationships between these risk factors and the PLR. The evidence here shows that many AD risk factors, including traumatic brain injury, ocular and intracranial hypertension, alcohol consumption, depression, and diabetes, are directly related to changes in the PLR. Other risk factors currently lack sufficient literature to make any conclusions relating directly to the PLR but have shown links to impairments in the parasympathetic nervous system; further research should be conducted in these risk factors and their relation to the PLR.

Blunted pupil light reflex is associated with negative symptoms and working memory in individuals with schizophrenia

Two largely separate lines of research have documented altered pupillary dynamics in individuals diagnosed with schizophrenia. An older set of studies has demonstrated reductions in the pupillary light reflex (PLR) in individuals with schizophrenia; however, clinical and cognitive correlates of this blunted PLR have been relatively unexplored. More recently, a large body of work has demonstrated reductions in pupillary dilation in response to cognitive demands in individuals with schizophrenia, and the degree of this blunted pupil dilation has been related to more severe cognitive deficits and motivational negative symptoms. These clinically relevant alterations in the cognitive modulation of pupil size have been interpreted as reflecting insufficient information processing resources or inappropriate effort allocation. To begin to bridge these two lines of work, we investigated the PLR in 34 individuals with schizophrenia and 30 healthy controls and related the amplitude of the PLR to motivational negative symptoms and cognitive performance. Consistent with prior work, we found that the PLR was reduced in individuals with schizophrenia, and furthermore, that these measurements were highly reliable across individuals. Blunted constriction was associated with more severe motivational negative symptoms and poorer working memory among individuals with schizophrenia. These observed correlates provide a bridge between older literature documenting an altered PLR and more recent work reporting associations between negative symptoms, cognition, and blunted pupillary dilation in response to cognitive demands in individuals with schizophrenia. We provide possible mechanistic interpretations of our data and consider a parsimonious explanation for reduced cognitive- and light-related modulation of pupil size.

Insomnia and suicide as reported adverse effects of second-generation antipsychotics and mood stabilizers

STUDY OBJECTIVES

Insomnia and suicide ideation/behavior/death (SIB) are common in psychiatric disorders. There is evidence that clozapine and lithium have antisuicidal properties and beneficial effects on sleep. We investigated the reported odds of spontaneously reported psychiatric adverse drug reactions of insomnia and SIB in adults for second-generation antipsychotics (SGAs) and mood stabilizers compared to clozapine and lithium, respectively.

METHODS

We searched the U.S. Food & Drug Administration Adverse Event Reporting System from inception through February 2021 for which an SGA or mood stabilizer was the suspected agent of a psychiatric adverse drug reaction.

RESULTS

We investigated 10 SGAs and 5 mood stabilizers. Compared to clozapine, other SGAs were associated with a significantly increased reported odds of insomnia (reported odds ratio [rOR] = 2.41-9.70) and SIB (rOR = 1.18-2.72). Compared to lithium, there was a significantly increased reported odds of SIB (rOR = 1.17-1.70) for other mood stabilizers and odds of insomnia (rOR = 1.66) for lamotrigine. The insomnia and SIB rORs for SGAs and mood stabilizers were positively correlated.

CONCLUSIONS

Our results are consistent with evidence for antisuicidal properties of clozapine and lithium. Findings also raise the possibility of beneficial effects on sleep as one potential pathway underlying the antisuicidal properties for these agents. Future studies are needed to identify underlying biological mechanisms that contribute to these associations.

CITATION

Miller BJ, McCall WV. Insomnia and suicide as reported adverse effects of second-generation antipsychotics and mood stabilizers. J Clin Sleep Med. 2022;18(2):517-522.

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.

Insomnia and inflammation in phase 1 of the clinical antipsychotic trials of intervention effectiveness study

Insomnia and inflammation are both common in schizophrenia. In the general population, insomnia is associated with inflammation. In n=519 subjects from the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) schizophrenia trial, terminal insomnia was investigated as an indicator of inflammation using non-parametric ANCOVA. After controlling for potential confounders, insomnia was significantly associated with higher blood IL-6 (F=4.12, p=0.007) and leptin (F=9.67, p<0.001) with large effect sizes (d=1.03 and d=0.79, respectively). Findings suggest that the assessment of insomnia is relevant to studies of inflammation in schizophrenia, and germane to trials of adjunctive hypnotics and anti-inflammatory agents in these patients.