Genetics of suicide: an overview

Genetics of suicide: a systematic review of twin studies

OBJECTIVES

Convergent evidence from a multitude of research designs (adoption, family, genomescan, geographical, immigrant, molecular genetic, surname, and twin studies of suicide) suggests genetic contributions to suicide risk. The present account provides a comprehensive and up-to-date review of the twin studies on this topic.

METHODS

A total of 32 studies (19 case reports, 5 twin register-based studies, 4 population-based epidemiological studies, 4 studies of surviving co-twins) located through extensive literature search strategies are summarized and discussed here. This literature corpus was published between 1812 and 2006 in six languages and reports data from 13 countries.

RESULTS

A meta-analysis of all register-based studies and all case reports aggregated shows that concordance for completed suicide is significantly more frequent among monozygotic than dizygotic twin pairs. The results of co-twin studies rule out exclusively psychosocially based explanations of this pattern. Population-based epidemiological studies demonstrate a significant contribution of additive genetic factors (heritability estimates: 30-55%) to the broader phenotype of suicidal behavior (suicide thoughts, plans and attempts) that largely overlaps for different types of suicidal behavior and is largely independent of the inheritance of psychiatric disorders. Nonshared environmental effects (i.e. personal experiences) also contribute substantially to the risk of suicidal behavior, whereas effects of shared (family) environment do not.

CONCLUSIONS

The totality of evidence from twin studies of suicide strongly suggests genetic contributions to liability for suicidal behavior. To further research progress in this area, an extensive discussion of design limitations, shortcomings of the literature and further points is provided, including sources of bias, gaps in the literature, errors in previous reviews, age and sex effects and twin-singleton differences in suicide risk, and notes from a history-of-science view.

Social Modeling in the Transmission of Suicidality

Abstract. Evidence from twin, adoption, and family studies suggests that there is strong aggregation of suicidal behaviors in some families. By comparison, the role of social modeling through peers has yet to be convincingly established. This paper uses data from four large studies (the WHO/EURO Multicentre Study on Suicidal Behaviour, the WHO/SUPRE-MISS, the CASE study, and the Queensland Suicide Register) to compare the effects of exposure to fatal and nonfatal suicidal behavior in family members and nonfamilial associates on the subsequent suicidal behavior of male and female respondents of different ages. Across all studies, we found that prior suicidal behaviors among respondents' social groups were more important predictors of suicidal behavior in the respondents themselves than previous research had indicated. Community-based suicide attempters in the WHO SUPRE-MISS had higher rates of exposure to prior suicide in nonfamilial associates than in family members. In an adolescent population, exposure to prior fatal suicidal behavior did not predict deliberate self-harm when exposure to nonfatal suicidal behavior (both familial and social) were controlled for, but exposure to nonfatal suicidal behaviors in family and friends was predictive of deliberate self-harm and suicide ideation, even after controlling for exposure to fatal suicidal behavior. The potential impact of “containment” of information regarding suicidal behaviors as a prevention initiative is discussed, in light of information behavior principles of social marketing.

No association of COMT Val158Met polymorphism with suicidal behavior or CSF monoamine metabolites in mood disorders

The Met allele of the Catechol-O-Methyltransferase (COMT) gene functional polymorphism (COMT-V158M) is associated with lower enzymatic activity than the Val allele and is reported to be associated with aggression, depression, and suicidal behavior. Since depression and impulsive-aggressive behavior may mediate risk for suicidal behavior, we assessed the association of this polymorphism with suicidal behavior. Clinical (impulsive aggression) and biological (CSF monoamine metabolites) endophenotypes were tested as potential mediators of the effect of genotype on suicide risk. Subjects with mood disorders (N = 486) and healthy volunteers (N = 119), all European Caucasian, were genotyped for COMT-V158M and assessed for DSM IV diagnoses, lifetime suicidal behavior, lifetime impulsivity, hostility, and aggression. CSF monoamine metabolites were assayed in a sub-sample of mood disorder patients (N = 111). We found no association between genotype and mood disorder diagnosis or with reported history of suicide attempt in mood disorder subjects. There was no association between genotype and lethality or method of suicide attempt, or with aggressive/impulsive traits. Further, there was no difference in monoamine metabolites by genotype. The COMT-V158M polymorphism was not associated with suicidal behavior in a Caucasian sample of mood disorder subjects, or with possible clinical or biological endophenotypes.

Pharmacogenetics of major depression: insights from level 1 of the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) trial

Major depression is a serious mental illness frequently associated with devastating consequences for those affected. Suicide rates are significantly elevated, creating a sense of urgency to identify effective yet safe treatment options. A plethora of antidepressants are available on the market today, designed to act on different neurotransmitter systems in the brain, providing the clinician with several treatment strategies. There is, however, very little guidance as to which antidepressant may be most successful in a certain individual. Biomarkers that can predict treatment outcome would thus be of great value, shortening the time until remission and reducing costs for the healthcare system by reducing unsuccessful treatment attempts. The proven contribution of heredity to major depression risk suggests that genetic markers may be good biomarkers for treatment outcome.The Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study and a large ancillary pharmacogenetic study in 1953 STAR*D participants constitute the largest effort to date to identify genetic predictors of antidepressant treatment outcome. In this review, the results of candidate gene studies carried out so far are summarized and discussed, and some future directions are proposed.

The relationship of impulsive aggressiveness to suicidality and other depression-linked behaviors

Suicide is a leading cause of death worldwide, among the top 10 causes of death in every country, and one of the three leading causes of death for people aged 15 to 34 years. It has been increasingly recognized in recent years that people who attempt or commit suicide have a certain individual predisposition, part of which is given by personality traits, and in particular, impulsive-aggressive behaviors. This article reviews evidence suggesting that impulsive-aggressive traits are part of a developmental cascade that increases suicide risk among a subset of suicides. These personality traits, which do not appear to be a consequence of psychiatric disorder, seem to play a larger role among younger suicides and may mediate familial transmission of suicidal behavior. However, not all suicides are associated with impulsive-aggressive behaviors, and we need to better understand vulnerability to suicide among non-impulsive-aggressive suicide.

Surname study of suicide in Austria: differences in regional suicide rates correspond to the genetic structure of the population

OBJECTIVES

There is convergent evidence from adoption, family, geographical, immigrant, molecular genetic, twin and, most recently, surname studies of suicide for genetic contributions to suicide risk. Surnames carry information about genetic relatedness or distance and, in patrilineal surname systems, are a close substitute for Y-chromosome markers and haplotypes, since surname transmission is similar to the transmission of the nonrecombining part of the Y chromosome. This study investigated whether differences in regional suicide rates correspond to the genetic structure of the Austrian population.

METHODS

Differences in district-level standardized suicide rates 1988-94 between the five major surname regions identified for Austria were analyzed. The surname regions used in the analysis reflect the contemporary population structure and closely follow the natural borders found in the topography of Austria, less so its administrative division into nine states.

RESULTS

Surname region accounted for a significant (P < 0.001) and substantial (38%) portion of the variance in district-level suicide rates. Adjusting the suicide rates for a set of five social and economic indicators that are established ecological correlates of suicide prevalence (income, and rates of the divorced, unemployed, elderly and Roman Catholics) left the results essentially unchanged.

CONCLUSIONS

Regional differences in suicide rates within Austria correspond to the genetic structure of the population. The present evidence adds to related findings from geographical and surname studies of suicide that suggest a role for genetic risk factors for suicidal behavior. Genetic differences between subpopulations may partially account for the geography of suicide. Study limitations and directions for future research are discussed.

Testing the Finno-Ugrian suicide hypothesis: replication and refinement with regional suicide data from eastern Europe

Multiple lines of evidence indicate specific genetic contributions to suicidal behavior. In particular, geographic studies support the Finno-Ugrian Suicide Hypothesis, i.e., genetic differences between populations may partially account for geographic patterns of suicide prevalence. Specifically, within Europe the high suicide-rate nations constitute a contiguous J-shaped belt. The present research replicated and extended 2003 findings of Voracek, Fisher, and Marusic with new data. Across 37 European nations, an interaction term of squared latitude multiplied with longitude (quantifying the J-shaped belt) accounted for 32% of the cross-national variance in total suicide rates alone, while latitude accounted merely for 18% of variance over and above those. Refined analysis included regional data from countries critical for testing the hypothesis (89 regions of Belarus, western Russia, and the Ukraine) and yielded an even more clear-cut pattern (56% and 3.5%, respectively). These results are consistent with the Finno-Ugrian Suicide Hypothesis. Study limitations and directions for further research are discussed.

Ancestry, genes, and suicide: a test of the Finno-Ugrian Suicide Hypothesis in the United States

There is now convergent evidence from classic quantitative genetics (family, twin, and adoption studies) and molecular genetic studies for specific genetic risk factors for suicidal behavior. This emerging research field has recently been supplemented by geographical studies concerned with the Finno-Ugrian Suicide Hypothesis (FUSH), which states that population differences in genetic risk factors may partially account for conspicuous geographical patterns seen in suicide prevalence. In particular, the European high-suicide-rate nations constitute a contiguous, J-shaped belt, spanning from Finland to Austria. This area maps onto the second principal component identified for European gene distribution, most likely reflecting a major migration event of the past (i.e., the ancestral adaptation to cold climates and the Uralic language dispersion) still detectable in modern European populations. The present research tested the hypothesis in the United States. Consistent with the hypothesis, available historical (1913-1924 and 1928-1932) U.S. state suicide rates were uniformly positively associated with available state proportions of reported American ancestries from European high-suicide-rate countries (Hungary, Lithuania, Poland, Russia, Slovakia, and the Ukraine). However, contrary to the hypothesis, available contemporary (1990-1994) suicide rates were uniformly negatively associated with these ancestry proportions. The findings of this first test outside Europe are therefore conflicting. A proposal based on the geographical study approach is offered to further the progress of investigations into the genetics of suicide.

Medical and psychology students' disbelief in the inheritance of risk factors for suicide

Despite convergent evidence for a role of genetic risk factors for suicide stemming from quantitative genetic (family, twin, and adoption designs), molecular genetic, and geographical studies, professionals, likely to be exposed to suicide, appear to disbelieve strongly in the inheritance of risk factors for suicide. In a sample of 1,093 Austrian medical and psychology students, about 80% of respondents did not endorse genetic risk factors for suicide, regardless of their sex, age bracket, field and year of study, and overall knowledge on suicide facts. This may reflect educational gaps, cognitive biases against genetic bases and explanations, or both. One single implication is that this information needs to be incorporated and covered more visibly in medical and psychology textbooks and curricula.

The serotonin transporter gene: polymorphism and haplotype analysis in Russian suicide attempters

The focus on gender-specific genes associated with female suicide is justified by the possible dimorphic nature of the serotonergic system and by the greater number of suicide attempts in females. We performed analysis of the promoter (5-HTTLPR) and intron 2 (STin2 VNTR) polymorphisms and haplotypes of the serotonin transporter gene in Russian suicide attempters, separately in men and women. Our findings indicate the contribution of the SLC6A4 gene to susceptibility for suicidal behavior in women, but not in men. The L/L genotype (p = 0.013, OR = 2.09) and L10 haplotype (p = 0.04, OR = 1.77) were associated with suicide in Russian women only. Further investigations of this gene in different phenotypic groups are necessary.

Antidepressants and suicidal behavior in bipolar disorder

Patients with bipolar disorder are at very high risk for suicidal ideation, non-fatal suicidal behaviors and suicide and are frequently treated with antidepressants. However, no prospective, randomized, controlled study specifically evaluating an antidepressant on suicidality in bipolar disorder has yet been completed. Indeed, antidepressants have not yet been shown to reduce suicide attempts or suicide in depressive disorders and may increase suicidal behavior in pediatric, and possibly adult, major depressive disorder. Available data on the effects of antidepressants on suicidality in bipolar disorder are mixed. Considerable research indicates that mixed states are associated with suicidality and that antidepressants, especially when administered as monotherapy, are associated with both suicidality and manic conversion. In contrast, growing research suggests that antidepressants administered in combination with mood stabilizers may reduce depressive symptoms in patients with bipolar depression. Further, the only prospective, long-term study evaluating antidepressant treatment and mortality in bipolar disorder, although open-label, found antidepressants and/or antipsychotics in combination with lithium, but not lithium alone, reduced suicide in bipolar and unipolar patients (Angst F, et al. J Affect Disord 2002: 68: 167-181). We conclude that antidepressants may induce suicidality in a subset of persons with depressive (and probably anxious) presentations; that this induction may represent a form of manic conversion, and hence a bipolar phenotype, and that lithium's therapeutic properties may include the ability to prevent antidepressant-induced suicidality.

Differing correlates for suicide attempts among patients with schizophrenia or schizoaffective disorder in India and USA

BACKGROUND

Suicide is one of the most common causes of death among persons with schizophrenia. Differing risk factors have been identified in published studies. The differences may have arisen because a uniform set of variables was not analyzed. Alternatively, the nature and effect of risk factors may vary in different settings. To test these possibilities, we investigated the same set of variables in two independent cross-national samples ascertained using identical protocols.

METHODS

Patients with schizophrenia or schizoaffective disorder (DSM IV criteria) were recruited in India (n=460) and the USA (n=424).

RESULTS

Consistent with earlier publications, a diagnosis of schizoaffective disorder, history of depression, pattern of symptoms and educational status were significantly associated with suicide attempts in the US sample. None of these variables were significantly associated in the Indian sample.

CONCLUSIONS

The impact of known risk factors for suicide attempts among patients with schizophrenia differs across ethnic groups.

Personality traits as correlates of suicidal ideation, suicide attempts, and suicide completions: a systematic review

OBJECTIVE

Involvement of personality traits in susceptibility to suicidality has been the subject of research since the 1950s. Because of the diversity of conceptual and methodological approaches, the extent of their independent contribution has been difficult to establish. Here, we review conceptual background and empirical evidence investigating roles of traits in suicidal behaviors.

METHOD

We selected original studies published in English in MEDLINE and PsycINFO databases, focusing on suicidal ideation, suicide attempts, or suicide completions, and using standardized personality measures.

RESULTS

Most studies focused on investigating risk for suicide attempts. Hopelessness, neuroticism, and extroversion hold the most promise in relation to risk screening across all three suicidal behaviors. More research is needed regarding aggression, impulsivity, anger, irritability, hostility, and anxiety.

CONCLUSION

Selected personality traits may be useful markers of suicide risk. Future research needs to establish their contributions in relation to environmental and genetic variation in different gender, age, and ethnocultural groups.

Rapid mood switching and suicidality in familial bipolar disorder

OBJECTIVES

Rapidly alternating or mixed mood states in bipolar disorder are associated with a particularly high risk for suicidal behavior. Are individuals with these patterns of illness more likely to develop suicidal intentions, or are they less able to resist them? This analysis examines the specific contribution of rapid switching and other variables to the relative likelihood of having or acting on self-reported suicidal thought and action, in a large group of individuals with bipolar disorder.

METHODS

The analysis included 1574 family members with bipolar disorder interviewed for a multi-site bipolar disorder genetic linkage study. Two models were tested, using the same set of demographic and clinical data points as independent variables. One model tested the influence of rapid switching and other variables on self-reported suicidal thought or action (i.e., suicidality), while the other tested the influences on suicidal action only among those who reported a history of suicidality.

RESULTS

Over 75% of subjects had contemplated suicide and 38% reported a history of suicidal behavior. A history of rapid switching was associated with higher likelihood of a history of suicidality, as was panic disorder. Familial suicidal behavior, as well as drug abuse, increased the likelihood of suicidal action among suicidal individuals, but did not increase the likelihood of becoming suicidal. Female sex, early age at onset, and several demographic factors were associated with both facets of suicidality.

CONCLUSIONS

Factors associated with high acuity of distress, such as panic attacks and unstable moods, appear to enhance the risk of suicidality in general. Factors that affected the threshold for action without increasing suicidality overall can also be seen as markers of impulsive decision-making. Of the two distinct kinds of suicidal risk, the latter - the likelihood of action given intent - appears to be the more familial.

Suicide in classical mythology: cues for prevention

OBJECTIVE

To compare well established antecedents and correlates of completed suicide with the motives and the mechanics reported in Greek mythology.

METHOD

A well-known collection of Greek myths, the Book of fables by Hyginus, was explored to investigate the mechanics driving an individual to imagine, design and carry out a suicide attempt.

RESULTS

Females outnumber males in the mythographer's list, their favourite methods to die being drowning, hanging, self-burning and throwing themselves down from on high. Some kind of familial recurrence of suicide was accounted for, and a large percentage of these suicides was connected to incest. Shame, sense of guilt and grief for the death of a loved one are the most frequently reported psychological correlates of the act, whereas defeat, failure or a catastrophic change in living conditions and, among females, an unfortunate love affair figure as the main antecedents of suicide.

CONCLUSION

Negative life events and emotional reactions to the severing of social ties frequently occur as antecedents of suicide in Greek mythology.