Overlapping genetic effects between suicidal ideation and neurocognitive functioning

Using the Strategy of Genome-Wide Association Studies to Identify Genetic Markers of Suicidal Behavior: A Narrative Review

BACKGROUND

Several studies involving various suicidal phenotypes based on the strategy of the search of genome-wide associations with single nucleotide polymorphisms have been performed recently. These studies need to be generalized.

AIM

To systematize the findings of a number of genome-wide association studies (GWAS) for suicidal phenotypes, annotate the identified markers, analyze their functionality, and possibly substantiate the hypothesis holding that these phenotypes reflect a nonspecific set of gene variants that are relevant as relates to stress-vulnerability as a key endophenotype of suicidal behavior (SB).

METHODS

A search on the PubMed and related resources using the combinations "suicide AND GWAS" and "suicidal behavior AND GWAS" was performed. It yielded a total of 34 independent studies and meta-analyses.

RESULTS

For the 10 years since such studies emerged, they have undergone significant progress. Estimates of the SNP heritability of SB in some cases are comparable with estimates of heritability based on the twin method. Many studies show a high genetic correlation with the genomic markers of the most common mental disorders (depression, bipolar disorder, schizophrenia, post-traumatic stress disorder). At the same time, a genomic architecture specific to SB is also encountered. Studies utilizing the GWAS strategy have not revealed any associations of SB with candidate genes that had been previously studied in detail (different neurotransmitters, stress response system, polyamines, etc.). Frequently reported findings from various studies belong in three main groups: 1) genes involved in cell interactions, neurogenesis, the development of brain structures, inflammation, and the immune responses; 2) genes encoding receptors for neurotrophins and various components of the intracellular signaling systems involved in synaptic plasticity, embryonic development, and carcinogenesis; and 3) genes encoding various neuro-specific proteins and regulators.

CONCLUSION

In general, GWAS in the field of suicidology mainly serve the purpose of a deeper understanding of the pathophysiology of suicidal behavior. However, they also demonstrate growing capability in terms of predicting and preventing suicide, especially when calculating the polygenic risk score among certain populations (psychiatric patients) and in combination with tests of different modalities. From our point of view, there exists a set of markers revealed by the GWAS strategy that seems to point to a leading role played by stress vulnerability, an endophenotype that is formed during early development and which subsequently comes to play the role of key pathogenetic mechanism in SB.

Genetics and epigenetics of self-injurious thoughts and behaviors: Systematic review of the suicide literature and methodological considerations

Suicide is a multifaceted and poorly understood clinical outcome, and there is an urgent need to advance research on its phenomenology and etiology. Epidemiological studies have demonstrated that suicidal behavior is heritable, suggesting that genetic and epigenetic information may serve as biomarkers for suicide risk. Here we systematically review the literature on genetic and epigenetic alterations observed in phenotypes across the full range of self-injurious thoughts and behaviors (SITB). We included 577 studies focused on genome-wide and epigenome-wide associations, candidate genes (SNP and methylation), noncoding RNAs, and histones. Convergence of specific genes is limited across units of analysis, although pathway-based analyses do indicate nervous system development and function and immunity/inflammation as potential underlying mechanisms of SITB. We provide suggestions for future work on the genetic and epigenetic correlates of SITB with a specific focus on measurement issues.

Theory of Mind and Suicidality: A Meta-Analysis

OBJECTIVE

Disturbances in interpersonal functioning are prevalent in individuals with suicidality. Foundational for interpersonal functioning is theory of mind (ToM), a social-cognitive ability that allows individuals to understand the thoughts and feelings of others. Recent work has begun to investigate ToM performance in individuals with suicidality, though no review has quantitatively aggregated findings from these varied studies. The current study investigated the relations between ToM and suicidality with meta-analysis.

METHOD

We identified and meta-analyzed 15 studies that presented data for 2,895 participants (617 of whom had reported at least one suicide attempt).

RESULTS

Results indicated a significant, negative relation between ToM and suicidality with a medium overall effect size (g = -.475). Moderator analyses revealed that this effect was consistent across age, sex, ToM content, and suicidal outcome.

CONCLUSION

Deficits in ToM associated with suicidality hold promise for risk-identification, treatment, and prevention work.HighlightsTheory of mind (ToM) abilities are critical for effective interpersonal functioning.Meta-analytics results indicate that ToM deficits are associated with suicidality.Identifying such suicidality-related ToM deficits may inform risk-identification, treatment, and prevention work.

A scoping review and comparison of approaches for measuring genetic heterogeneity in psychiatric disorders

An improved understanding of genetic etiological heterogeneity in a psychiatric condition may help us (a) isolate a neurophysiological 'final common pathway' by identifying its upstream genetic origins and (b) facilitate characterization of the condition's phenotypic variation. This review aims to identify existing genetic heterogeneity measurements in the psychiatric literature and provides a conceptual review of their mechanisms, limitations, and assumptions. The Scopus database was searched for studies that quantified genetic heterogeneity or correlation of psychiatric phenotypes with human genetic data. Ninety studies were included. Eighty-seven reports quantified genetic correlation, five applied genomic structural equation modelling, three evaluated departure from the Hardy-Weinberg equilibrium at one or more loci, and two applied a novel approach known as MiXeR. We found no study that rigorously measured genetic etiological heterogeneity across a large number of markers. Developing such approaches may help better characterize the biological diversity of psychopathology.

Genome-wide association study of suicidal behaviour severity in mood disorders

OBJECTIVE

Suicide is a major public health problem and it has a prominent genetic component. We performed a genome-wide association study (GWAS) of suicidal behaviour severity.

METHODS

Suicide behaviour severity was assessed within the Schedules for Clinical Assessment in Neuropsychiatry in our mood disorder sample (n = 3506) for the GWAS. We also performed polygenic risk score analyses to explore genetic sharing between suicidal behaviour severity and a number of phenotypes, including bipolar disorder, major depressive disorder, alcoholism, post-traumatic stress disorder, impulsivity, insomnia, educational attainment, loneliness, maltreatment, and amygdala volume.

RESULTS

We did not detect genome-wide significant findings at the single-marker or gene level. We report a number of suggestive single-marker and gene-based findings. Our polygenic risk score analyses did not yield significant findings with these phenotypes.

CONCLUSIONS

Larger sample sizes are required to detect moderate effects.

Neurocognitive Functioning in Adolescents at Risk for Suicidal Behaviors

Today, little is still known about the neurocognitive functioning of the individual at risk for suicide in a relevant developmental stage like adolescence. Thus, the main goal of the present work was to analyze the neurocognitive performance of adolescents at high risk for suicide. A total of 1509 adolescents from a stratified random cluster sampling were selected. Adolescents at risk for suicidal behaviors included 83 participants. A comparison group of 83 participants matched by age and gender was also randomly selected from the sample. The Paykel Suicide Scale (PSS) and the University of Pennsylvania Computerized Neurocognitive Battery for children (included 14 tasks assessing five neurobehavioral domains: executive functions, episodic memory, complex cognition, social cognition, and sensorimotor speed) were used. Adolescents at risk for suicide revealed statistically significant impairments across different neurocognitive domains including complex cognition, episodic memory and social cognition. No significant differences were found for Sensorimotor and Executive Function domains. Results found in the present study contribute relevant information about the nature of the neurocognitive impairments associated with suicide and add information in order to deeper comprehend the tentative etiology of suicide thoughts and attempts in adolescents with the aim to establish preventive treatments.

Preliminary analysis of low-level alcohol use and suicidality with children in the adolescent brain and cognitive development (ABCD) baseline cohort

Cross-sectional analyses were conducted in the baseline cohort of the Adolescent Brain and Cognitive Development (ABCD) Study to determine if lifetime low-level alcohol use was associated with an increased likelihood of lifetime suicidality (N=10,773, ages 9-10). Among the lifetime suicide ideation and attempt groups, 37.7% and 36.2% reported lifetime low-level alcohol use, respectively; versus 22.2% in the non-suicidality group. Children reporting lifetime alcohol use (i.e., ≥ a sip) showed a nearly two-fold increase in their odds of lifetime suicidality compared to those with no previous alcohol use. Future prospective research with this cohort will continue to probe alcohol-suicidality associations.