Contribution of genes and environment to the longitudinal association between childhood impulsive-aggression and suicidality in adolescence

Genetics of child aggression, a systematic review

Excessive and persistent aggressiveness is the most common behavioral problem that leads to psychiatric referrals among children. While half of the variance in childhood aggression is attributed to genetic factors, the biological mechanism and the interplay between genes and environment that results in aggression remains elusive. The purpose of this systematic review is to provide an overview of studies examining the genetics of childhood aggression irrespective of psychiatric diagnosis. PubMed, PsycINFO, and MEDLINE databases were searched using predefined search terms for aggression, genes and the specific age group. From the 652 initially yielded studies, eighty-seven studies were systematically extracted for full-text review and for further quality assessment analyses. Findings show that (i) investigation of candidate genes, especially of MAOA (17 studies), DRD4 (13 studies), and COMT (12 studies) continue to dominate the field, although studies using other research designs and methods including genome-wide association and epigenetic studies are increasing, (ii) the published articles tend to be moderate in sizes, with variable methods of assessing aggressive behavior and inconsistent categorizations of tandem repeat variants, resulting in inconclusive findings of genetic main effects, gene-gene, and gene-environment interactions, (iii) the majority of studies are conducted on European, male-only or male-female mixed, participants. To our knowledge, this is the first study to systematically review the effects of genes on youth aggression. To understand the genetic underpinnings of childhood aggression, more research is required with larger, more diverse sample sets, consistent and reliable assessments and standardized definition of the aggression phenotypes. The search for the biological mechanisms underlying child aggression will also benefit from more varied research methods, including epigenetic studies, transcriptomic studies, gene system and genome-wide studies, longitudinal studies that track changes in risk/ameliorating factors and aggression-related outcomes, and studies examining causal mechanisms.

Reconsidering the failure model: Using a genetically controlled design to assess the spread of problems from reactive aggression to internalizing symptoms through peer rejection across the primary school years

According to the failure model (Patterson & Capaldi, 1990), peer rejection is the intermediary link between problem behaviors and internalizing symptoms. The present study tested the model with 464 monozygotic and same-sex dizygotic twin pairs (234 female, 230 male dyads). Teacher-reported reactive aggression and internalizing symptoms, and peer-reported peer rejection were collected at ages 6, 7, and 10 (from 2001 to 2008). Support for the failure model emerged in conventional non-genetically controlled analyses, but not twin-difference score analyses (which remove shared environmental and genetic contributions). Univariate biometric models attributed minimal variance in failure model variables to shared environmental factors, suggesting that genetic factors play an important unacknowledged role in developmental pathways historically ascribed to nonshared experiences in the failure model.

Mood Disorders and Aggressive Traits Mediate Effects of Reported Childhood Adversity on Suicide Attempt Risk

BACKGROUND

Childhood adversity (CA) is linked to suicidal behavior as well as to mood disorders and aggressive traits. This raises the possibility that depression and aggressive traits mediate the relationship of childhood adversity to suicide risk. Moreover, it is not known if they operate independently or interactively.

AIMS

To determine whether, and how, mood disorders and aggressive traits mediate the effects of reported physical and sexual abuse on future suicidal behavior.

METHODS

Five hundred and forty-eight subjects, offspring of parents with mood disorders, were interviewed at baseline and at yearly follow-ups with questionnaires assessing aggression, mood disorders, and suicidal behavior. The mediation analysis involved a three-step process, testing the relationships between (1) CA and attempt; (2) CA and putative mediators; and (3) putative mediators and suicide attempt, adjusting for CA.

RESULTS

Aggressive trait severity and mood disorder onset each mediated the relationship between CA and future suicide attempts. Greater aggression severity also raised the hazard of the development of a mood disorder. If aggressive trait severity was clearly elevated, then onset of mood disorder did not increase further the hazard of the suicide attempt. Including family as a random effect had a much bigger effect on attempt outcome for physical abuse compared with sexual abuse.

CONCLUSIONS

Amelioration of aggressive traits and treatment of mood disorders in CA-exposed offspring of a parent with a mood disorder may prevent future suicide attempts and may reduce the risk of mood disorder. Familial factors influence the impact of childhood physical abuse but not sexual abuse. HIGHLIGHTSChildhood Adversity (CA) predicted future mood disorder and aggression severity.Depression and aggression mediate the relationship between CA and suicide attempts.When one mediator is present, the presence of the other does not increase the hazard.Between family variation contributed much more to suicidal behavior outcomes relative to the effect of physical abuse, but sexual abuse contributed to suicidal outcomes more than family variation.

Risks and familial coaggregation of death by suicide, accidental death and major psychiatric disorders in first-degree relatives of individuals who died by suicide

BACKGROUND

Evidence suggests a familial coaggregation of major psychiatric disorders, including schizophrenia, bipolar disorder, major depression (MDD), autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). Those disorders are further related to suicide and accidental death. However, whether death by suicide may coaggregate with accidental death and major psychiatric disorders within families remains unclear.

AIMS

To clarify the familial coaggregation of deaths by suicide with accidental death and five major psychiatric disorders.

METHOD

Using a database linked to the entire Taiwanese population, 68 214 first-degree relatives of individuals who died by suicide between 2003 and 2017 and 272 856 age- and gender-matched controls were assessed for the risks of death by suicide, accidental death and major psychiatric disorders.

RESULTS

A Poisson regression model showed that the first-degree relatives of individuals who died by suicide were more likely to die by suicide (relative risk RR = 4.61, 95% CI 4.02-5.29) or accident (RR = 1.62, 95% CI 1.43-1.84) or to be diagnosed with schizophrenia (RR = 1.53, 95% CI 1.40-1.66), bipolar disorder (RR = 1.99, 95% CI 1.83-2.16), MDD (RR = 1.98, 95% CI 1.89-2.08) or ADHD (RR = 1.34, 95% CI 1.24-1.44).

CONCLUSIONS

Our findings identified a familial coaggregation of death by suicide with accidental death, schizophrenia, major affective disorders and ADHD. Further studies would be required to elucidate the pathological mechanisms underlying this coaggregation.

Association of parental death and illness with offspring suicidal ideation: cross-sectional study in a large cohort of university students

PURPOSE

The aim of this study was to (1) investigate the association of parental death and illness with suicidal ideation using a large sample of university students and (2) test whether associations were moderated by perceived family support.

METHODS

We used data from N = 15,008 French university students enrolled in the i-Share cohort (mean age, 20.5 years; 77% women). Students self-reported information on parental death, including the cause, parental illness (cardiovascular, stroke, cancer, depression/anxiety, alcohol abuse), and perceived family support during childhood/adolescence. Twelve-month suicidal ideation was self-reported and categorized into no, occasional, and frequent ideation.

RESULTS

Occasional and frequent suicidal ideation were, respectively, reported by 2692 (17.5%) and 699 (4.6%) students. After adjustment for age, gender, and parental education, we found associations between parental death and risk of occasional and frequent suicidal ideation (respectively, RR = 1.98 [1.81-2.17] and RR = 2.73 [2.30-3.24]). Parental deaths from illness, accidents, and suicides had the strongest associations. We also found associations for parental depression/anxiety (occasional, RR = 1.98 [1.81-2.17]; frequent, RR = 2.73 [2.30-3.24]), alcohol use problems (occasional, RR = 1.71 [1.5-1.94]; frequent, RR = 2.33 [1.89-2.87]), and cardiovascular diseases (occasional, RR = 1.22 [1.06-1.40]; frequent, RR = 1.83 [1.47-2.27]). For participants who experienced parental death and stroke, associations with occasional and frequent suicidal ideation (respectively) increased as perceived family support increased (Ps_interaction ≤ 0.005).

CONCLUSIONS

Students who experienced parental death and common parental illnesses were at risk of reporting suicidal ideation, especially if their family were perceived as an important source of support. As information on parental death or illness can be routinely collected during health visits, attention should be paid to students reporting such experiences.

Suicidal ideation during adolescence: The roles of aggregate genetic liability for suicide attempts and negative life events in the past year

BACKGROUND

Suicidal thoughts and behaviors (STB) constitute a central public health concern in adolescence. Previous studies emphasized the difficulty to cope with negative life events during adolescence as a risk factor for STB. Familial and genetic liability has also been documented to explain STB risk. Nevertheless, less is known about aggregate genetic liability and its possible interaction with negative life events. Moreover, information is needed to understand how these factors differently affect STB in boys and girls.

METHODS

We evaluated suicidal ideation at 17 years old and examined the role of aggregate genetic liability, negative life events, and their interaction in a sample of 2,571 adolescents. Aggregate genetic liability was measured using a polygenic score (PGS) for suicide attempts. Negative life events were assessed in the past year and included parental divorce and hospitalizations, death of friends and relatives, bullying, failure-related events, and involvement with drugs. We conducted univariable and multivariable general linear models stratified by sex and evaluated the interactions between PGS and negative life events in subsequent models.

RESULTS

Analyses showed that suicidal ideation in boys is associated with failure to achieve something important (estimate = 0.198), bullying (estimate = 0.285), drug use (estimate = 0.325), and parental death (estimate = 0.923). In girls, both aggregate genetic liability (estimate = 0.041) and negative life events (failure at school [estimate = 0.120], failure to achieve something important [estimate = 0.279], drug use [estimate = 0.395], and bullying [estimate = 0.472]) were associated with suicidal ideation. Interaction analyses suggested that PGS interacted with drug use and failures at school, though this would need additional support.

CONCLUSIONS

These findings represent significant contributions to the fundamental understanding of STB in adolescence, suggesting to monitor the impact of negative life events during adolescence to better prevent suicide risk. Genetic liability is also of importance in girls and might influence the way they respond to environmental threats.

Reactive vs proactive aggression: A differential psychobiological profile? Conclusions derived from a systematic review

INTRODUCTION

Scholars have established subcategories of aggressive behavior in order to better understand this construct. Specifically, a classification based on motivational underpinnings makes it possible to differentiate between reactive and proactive aggression. Whereas reactive aggression is characterized by emotional lability, which means it is prone to impulsive reactions after provocation, proactive aggression is driven by low emotionality and high levels of instrumentality to obtain benefits. Some authors have conceived these two types as having a dichotomous nature, but others argue against this conceptualization, considering a complementary model more suitable. Hence, neuroscientific research might help to clarify discussions about their nature because biological markers do not present the same biases as psychological instruments.

AIM

The main objective of this study was to carry out a systematic review of studies that assess underlying biological markers (e.g., genes, brain, psychophysiological, and hormonal) of reactive and proactive aggression.

METHODS

To carry out this review, we followed PRISMA quality criteria for reviews, using five digital databases complemented by hand-searching.

RESULTS

The reading of 3993 abstracts led to the final inclusion of 157 papers that met all the inclusion criteria. The studies included allow us to conclude that heritability accounted for approximately 45% of the explained variance in both types of aggression, with 60% shared by both, especially, for overt and physical expression forms, and 10% specific to each type. Regarding allelic risk factors, whereas low functioning variants affecting serotonin transport and monoaminoxidase increased the risk of reactive aggression, high functioning variants were associated with proactive aggression. Furthermore, brain analysis revealed an overlap between the two types of aggression and alterations in the volume of the amygdala and temporal cortex. Moreover, high activation of the medial prefrontal cortex (PFC) facilitated proneness to both types of aggression equally. Whereas stimulation of the right ventrolateral (VLPFC) and dorsolateral (DLPFC) reduced proneness to aggression, inhibition of the left DLPFC increased it. Finally, psychophysiological and hormonal correlates in general did not clearly differentiate between the two types because they were equally related to each type (e.g., low basal cortisol and vagal variability in response to acute stress) CONCLUSIONS: This study reinforces the complementary model of both types of aggression instead of a dichotomous model. Additionally, this review also offers background about several treatments (i.e., pharmacological, non-invasive brain techniques…) to reduce aggression proneness.

Identifying environmental pathways between irritability during childhood and suicidal ideation and attempt in adolescence: findings from a 20-year population-based study

BACKGROUND

Irritable children are at increased risk of suicidal ideation and suicide attempt, but the underlying environmental mechanisms accounting for these associations are largely unknown. We aimed to investigate the mediating role of peer victimization and harsh parenting in the association between childhood irritability and adolescent suicidal ideation and attempt.

METHOD

N = 1,483 participants from the Québec Longitudinal Study of Child Development followed up from 5 months until 20 years of age (2018) with annual or biannual assessments. Irritability was operationalized using assessments of teacher-reported temper tantrums and reactive aggression. Suicidal ideation and suicide attempt at ages 13, 15, 17, and 20 years were self-reported. Peer victimization (self-reported at age 13) and harsh parenting (mothers reported at age 13) were considered as potential mediators.

RESULTS

We identified four trajectories of teacher-reported irritability symptoms from 6 to 12 years: low (74.8%), rising (12.9%), declining (7.3%), and persistent (4.9%). In adjusted models, children in the persistent and rising trajectories had, respectively, 2.81-fold (CI, 1.27-6.22) and 2.14-fold (CI, 1.20-3.81) increased odds of suicide attempt in adolescence, but not suicidal ideation. We found that a significant proportion of the association between irritability trajectories and suicide attempt was mediated by peer victimization (33% and 35% for rising and persistent, respectively), but there was no mediation via harsh parenting.

CONCLUSIONS

Our findings suggest that peer victimization may be a key mechanism explaining the increased suicide attempt risk of children presenting with persistently high or increasing irritability. Interventions to reduce peer victimization may be helpful to reduce suicide risk among irritable children.