Suicidal Behaviors in Surviving Monozygotic and Dizygotic Co‐Twins: Is the Nature of the Co‐Twin's Cause of Death a Factor?

Genetically informative samples can address hereditary and experiential influences on suicide‐related behaviors. The frequency of suicide‐related behaviors was compared in twins from two survivor groups: (1) those whose co‐twins' deaths were suicides (monozygotic [MZ]: n = 47; dizygotic [DZ]: n = 31), and (2) those whose co‐twins' deaths were nonsuicides (MZ: n = 347; DZ: n = 170). The frequency of suicide attempts among suicide survivors was significantly higher in MZ than DZ twins, while the frequency of suicide attempts among nonsuicide twin survivors did not differ between MZ and DZ twins. Twin concordance for suicide attempts more likely reflects a genetic predisposition than a behavioral reaction to the loss.     

Twin imitation for antisocial behavior: implications for genetic and family environment research.

When twin pairs influence each other's behavior, observed variance is greater for MZ twins than for DZ twins under at least 1 of 2 conditions: (a) the trait has some heritability and (b) MZ twins influence each other more than do DZ twins. Applied to a trait that has an underlying continuous distribution but is measured as a dichotomy, the presence of reciprocal twin influence predicts that if the base rate for the trait is not exactly 50%, then the prevalence of the trait should differ in MZ and DZ twin pairs. This prediction held for registered criminality in a large twin cohort. Methods of analysis that permit reciprocal twin interaction not only provide better statistical fits to the data but also yield estimates of heritability that agree with adoption data. The results suggest that the genetic influence on registered criminality may be more modest than previously thought.     

Whose life is it anyway? Adoption of each other's autobiographical memories by twins

Anecdotal evidence suggests that twins may dispute ownership of autobiographical experiences. We investigated the frequency and characteristics of such disputed memories in comparison to memories with undisputed ownership. In the present study, monozygotic twins (MZ), dizygotic twins (DZ), and siblings were asked to remember disputed and non‐disputed memories. They also dated each memory and provided a rating on the following variables: level of imagery, detail, rehearsal, and importance. Results showed that disputed memories were more common among MZ twins than in DZ twins and siblings. The frequencies of undisputed memories were not different among the three groups. When compared to non‐disputed memories, disputed memories were more likely to come from events experienced during preschool years. We consider disputed memories as instances of false memories, at least partly influenced by social interactional processes, and event characteristics. Copyright © 2003 John Wiley & Sons, Ltd.     

Problems in Psychiatric Genetic Research: A Reply to Faraone and Biederman

This article examines evidence cited in favor of the operation of genetic factors in attention-deficit hyperactivity disorder (ADHD). Like other psychiatric conditions, a belief in the genetic basis of ADHD is derived from the results of family, twin, and adoption studies. Because family studies are widely believed to be confounded by environmental factors, primary emphasis is placed on twin and adoption studies. ADHD twin studies depend on the validity of the equal environment assumption (EEA), which holds that the environments of identical (MZ) and fraternal (DZ) twins are the same. Here it is argued that however the EEA is defined, it cannot be accepted. Therefore, the greater similarity or concordance of MZ twins when compared to DZ twins is plausibly explained by environmental factors. Adoption studies constitute a third method for investigating the role of genetic factors in ADHD. It is argued that these studies are greatly flawed by factors including non blinded diagnoses and the failure to study the biological relatives of adoptees. After an examination of the total weight of evidence in favor of a genetic basis or predisposition for ADHD, it is concluded that a role for genetic factors is not supported and that future research should be directed toward psychosocial causes     

Incidence of suicidal ideation and behavior in the United States, 1994.

Completed suicides reflect only a portion of the impact of suicidal behavior; sublethal behaviors cause morbidity and can signal treatable problems such as depression. There is no national quantification of nonlethal suicidal behaviors. The present study used a random-digit-dialed telephone survey to estimate the 12-month incidence of suicidal ideation, planning, and attempts among U.S. adults. Of 5,238 respondents, 5.6% (representing about 10.5 million persons) reported suicidal ideation, 2.7% (about 2.7 million) made a specific suicide plan, and 0.7% (about 700,000) made a suicide attempt (estimate = 1.1 million attempts). Hence, suicidal behaviors are not uncommon and occur along a continuum ranging from ideation to completed suicides. Preventing nonlethal precursor behaviors may prevent deaths.     

Mate choice and friendship in twins: evidence for genetic similarity

This study examined the genetic and environmental contribution to people's preference for spouses and friends to be similar to themselves. In their responses to 130 personality, attitude, and demographic questions, 174 pairs of monozygotic (MZ) twins resembled each other (r= .53) more than did 148 pairs of dizygotic (DZ) twins (r= .32), 322 pairs of spouses (r= .32), and 563 pairs of best friends (r= .20). It was not previously recognized that spouses and friends are as similar as DZ twins. MZ twins also chose spouses and best friends more similar to their co-twins' friends and spouses than did DZ twins (mean rs = .22 vs. .14). The twins' preference for spouses and friends similar to themselves was about 34% due to the twins' genes, 12% due to the twins' common environment, and 54% due to the twins' unique (nonshared) environment. Similarity to partners was more pronounced on the more heritable items than the less heritable items. It is concluded that people are genetically inclined to choose as social partners those who resemble themselves at a genetic level.     

Social closeness of MZ and DZ twin parents towards nieces and nephews

Twins' marriages to non‐twins yield genetically and socially informative kinships. Monozygotic (MZ) twins' genetic identity makes them ‘genetic parents’ of their nieces/nephews, and their nieces/nephews their ‘genetic children’. The present study is the first to apply twin‐family models to study social relatedness. Analyses of twin families (MZ: N = 248; DZ: N = 75) tested evolutionary‐based concepts concerning social closeness, perceived similarity and caretaking. Hypotheses based on Hamilton's inclusive fitness theory were supported: MZ twin aunts/uncles expressed greater social closeness towards their nieces/nephews than DZ twin aunts/uncles; and female twins from same‐sex pairs expressed greater closeness towards their nieces/nephews than male twins from same‐sex pairs. This study underlines benefits of associations between behavioural‐genetic and evolutionary psychological theories, methods and interpretations. Copyright © 2007 John Wiley & Sons, Ltd.     

Genetic and environmental influences on religiousness: findings for retrospective and current religiousness ratings

Estimates of the degree of genetic and environmental influences on religiousness have varied widely. This variation may, in part, be due to age differences in the samples under study. To investigate the heritability of religiousness and possible age changes in this estimate, both current and retrospective religiousness were assessed by self-report in a sample of adult male twins (169 MZ pairs and 104 DZ pairs, mean age of 33 years). Retrospective reports of religiousness showed little correlation difference between MZ (r=.69) and DZ (r=.59) twins. Reports of current religiousness, however, did show larger MZ (r=.62) than DZ (r=.42) similarity. Biometric analysis of the two religiousness ratings revealed that genetic factors were significantly weaker (12% vs. 44%) and shared environmental factors were significantly stronger (56% vs. 18%) in adolescence compared to adulthood. Analysis of internal and external religiousness subscales of the total score revealed similar results. These findings support the hypothesis that the heritability of religiousness increases from adolescence to adulthood.     

Tacit coordination in monozygotic twins, dizygotic twins and virtual twins: Effects and implications of genetic relatedness

Game theorists have long been interested in why some partners are more successful at achieving mutual goals than others. The present study was conducted to determine if tacit coordination (non-negotiated consensus) varies as a function of genetic relatedness between social partners. The sample included 7–13-year-old monozygotic (MZ) twin pairs (n = 53), dizygotic (DZ) twin pairs (n = 85) and virtual twin (VT) pairs (n = 42; same-age unrelated siblings). Co-twin agreement on questions completed under individual and coordination conditions was compared across the three groups. MZ twins showed significantly greater overall agreement than DZ twins and VTs, using multiple criteria. The implications of these findings are considered with reference to behavioral-genetic and evolutionary theories of behavior.     

Suicidal Ideation in Elderly Bereaved: The Role of Complicated Grief

This study examined whether symptoms of complicated grief at baseline predicted suicidal ideation during a depressive episode in elderly bereaved individuals. Over a 17-month period, serial ratings of suicidal ideation, hopelessness, and symptoms of depression, anxiety, and complicated grief were obtained from 130 elderly participants who had lost their spouses within the past 2 years. Groups of active and passive suicidal ideators, as well as nonideator controls, were compared via analysis of variance (ANOVA) with respect to levels of complicated grief, depression, and anxiety. Elderly bereaved with both active and passive suicidal ideation were found to have higher symptomatic levels of depression, hopelessness, complicated grief, and anxiety, as well as lower levels of perceived social support, than nonideators at study entry. Fifty-seven percent of the patients with high complicated grief scores were found to be ideators during the follow-up versus 24% of the patients with low complicated grief scores. Patients with any suicidal ideation had higher symptom levels of depression, anxiety, and complicated grief when they were ideators as compared with periods when they denied ideation. Fifteen out of the 39 ideators had recurrent depressive episodes versus 5 of the 91 nonideators. Patients with a history of suicide attempts were more likely to be ideators after loss than other bereaved. Thus, the condition of having high levels of complicated grief symptoms and depressive symptoms appears to make bereaved individuals vulnerable to suicidal ideation. Detection of high levels of complicated grief could help clinicians identify patients who may be at heightened risk for suicide.     

Is Cumulative Exposure to Suicide Attempts and Deaths a Risk Factor for Suicidal Behavior Among Firefighters? A Preliminary Study

The association between cumulative exposure to suicide attempts and deaths and suicidal behavior was examined in a sample of 61 professional firefighters. On average, firefighters reported 13.1 (SD = 16.6) exposures over the course of their lifetime. Cumulative exposure to suicide attempts and deaths was positively correlated with suicidal behavior (r = .38, p = .004). Moreover, firefighters with 12+ exposures were more likely to screen positive for risk of suicidal behavior (OR = 7.885, p = .02). Additional research on the potential impact of cumulative exposure to suicide attempts and deaths on firefighters' health and safety is needed.     

Reports of attempted suicide among Brazilian addicts

Both substance dependence and depressive mood seem to be associated with increased suicide risk. Clinical information on suicide attempts and depressive symptoms were obtained from a sample of 211 psychoactive substance dependents attending a university clinic program for addicts in Brazil. 49 subjects (23.4%) had attempted suicide at least once, and the frequency of reporting attempts was 4.32 times greater among women than among men. Male addicts also tended to engage in potentially more dangerous attempt methods than women. Depressive male addicts were 2.17 times more likely to have attempted suicide than nondepressive addicted men. Among women, no association could be established between having attempted suicide and the presence of depression. Substance addicts have a relatively high risk of attempting suicide and the co-occurrence of depression seems to increase prevalence of suicidal behavior among men.     

Suicidal behavior among inpatients with schizophrenia and mood disorders in Chengdu, China

This study evaluated the characteristics of suicidal behavior (suicide attempt or suicidal ideation) among 230 consecutively admitted inpatients with schizophrenia and mood disorders in a university hospital in China. The rate of lifetime suicidal behavior was found to be significantly higher in patients with mood disorders (62.4%) than in patients with schizophrenia (38.6%). The rate of suicidal behavior was significantly higher in patients with major depressive disorder (86.8%) than those with bipolar disorders (42.6%). Patients with schizophrenia attempted suicide for the first time earlier in life than the patients with mood disorders. Mood disorder patients, especially those with major depressive disorder, had more and more serious suicide attempts than the patients with schizophrenia.     

The last moments of life: Learning to cope

A large portion of youthful death in this country is caused by the intentional self‐destructive behavior of individuals who experience helplessness, alienation, loneliness, who suffer from social neglect, and who react to the loss of significant others. Analysts of youthful suicide view such events as being associated with attempts to cope with stress and crisis. This article describes those social forces that shaped the acts of suicide and provides a partial explanation for suicidal behavior among young people. As a strategy employed by the victims to cope with problems in living, suicide is, the author suggests, a plausible response to stress prompted in part by a fatalistic attitude.     

Relationship between quantity and frequency of alcohol use and indices of suicidal behavior in an elderly Australian sample

Relatively little research has been conducted on the relationship between alcohol misuse and suicidal behavior among the elderly. The current study's aim was to examine whether quantity and frequency of alcohol use and the interaction between these variables are related to current suicidal ideation, previous suicidal ideation/intent, and past suicide attempts in a community sample of 1,010 Australian adults over age 60. Results partially supported our hypotheses. The interaction between quantity and frequency of alcohol use was significant, suggesting that those who use alcohol less frequently but in greater quantities (i.e., binge drinking) are more likely to have a history of suicide attempts.     

云南省大学生自杀行为及相关因素分析

采用SCL-90、青少年生活事件量表、应对方式量表、社会支持评定量表和自编的外显行为量表对云南省3313名大学生进行了测查,并探讨了包括自杀意念及自杀企图在内的自杀行为状况及其影响因素。结果表明:(1)427(13.2%)名大学生有自杀意念,卡方检验显示女生人数显著多于男生;154(4.7%)名大学生有过自杀企图,男女生人数没有显著差异;(2)自杀意念和自杀企图在人口统计学变量上有显著差异:在自杀意念上,女生、独生子女、文科生、来自城市的学生和不完整家庭的学生、月支出少于100元的学生得分显著高于与之对应的大学生;而在自杀企图上,只有来自城市的学生和不完整家庭的学生、月支出少于100元的学生得分显著高于与之对应的大学生;(3)大学生自杀意念和自杀企图与心理症状、生活事件、情感中心应对呈显著的正相关,与问题中心应对、社会支持呈显著的负相关;(4)在结构模型中,社会支持在心理症状和自杀行为中起到显著的调节作用,情感中心应对在生活事件、社会支持、社会支持对心理症状的调节作用中起显著的中介作用,而问题中心应对在生活事件、社会支持、社会支持对事件的调节作用中起显著的中介作用。     

Correction to gonzalez (2012)

Reports an error in "Association of solitary binge drinking and suicidal behavior among emerging adult college students" by Vivian M. Gonzalez (Psychology of Addictive Behaviors, Advanced Online Publication, Jan 30, 2012, np). In the article, there is an error in the introductory paragraph. The number of students who had seriously considered attempting suicide in the Barrios, Everett, Simon, & Brener (2000) study should have been reported as 11.4%, not 1.4%. Additionally, in the Participants section, data for the study were collected from March 2009 to September 2010, not March 2009 to January 2010 as reported. (The following abstract of the original article appeared in record 2012-02608-001.) Emerging adult college students who binge drink in solitary contexts (i.e., while alone) experience greater depression and suicidal ideation than do students who only binge drink in social contexts, suggesting that they may be at greater risk for suicidal behavior. This study examined the association of a previous suicide attempt, one of the best predictors of future suicide attempts and suicide, and severity of recent suicidal ideation with drinking in solitary and social contexts. Participants were binge drinking, emerging adult (18- to 25-year-old) college students (N = 182) drawn from two studies of college drinkers. A logistic regression analysis revealed that both suicide attempt history and severity of suicidal ideation were significantly associated with a greater likelihood of being a solitary binge drinker as opposed to only a social binge drinker. Students with a previous suicide attempt were nearly four times more likely to be solitary binge drinkers. Multiple regression analyses revealed that suicide attempt history was significantly associated with greater frequency and quantity of drinking in solitary, but not social contexts. Suicidal ideation was significantly associated with drinks per solitary drinking day, but not frequency of solitary drinking once suicide attempt history was accounted for. Given the associations found between solitary binge drinking and a history of suicide attempts, as well as greater severity of recent suicidal ideation, it appears that these students are in need of suicide prevention efforts, including treatment efforts aimed at reducing binge drinking. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

“Principles in his nature which interest him in the fortune of others…”: The heritability of empathic concern for others1

The present research was conducted to explore genetic influences on empathic concern for others. First, an index of empathic concern was created by combining relevant items from Gough's Adjective Check List (ACL). This index was validated by correlating scores of 88 undergraduates on the index with their scores on a self-report measure of empathy, which has been related to prosocial behavior. Correlations were sufficiently high to accept the validity of the index. Next, previously collected ACL responses of 114 monozygotic (MZ) and 116 dizygotic (DZ) twins were reanalyzed in order to create an empathic concern score for each twin. The twins were middle-aged males initially raised together but living apart at the time they completed the ACL. Comparison of intraclass correlations for MZ and DZ twins revealed, as predicted by the genetic hypothesis, significant (p < .005) heritability in empathic concern scores. This finding suggests that there may, indeed, be a genetic influence on individual differences in empathic concern for others. Some limitations of the present data are also considered. How selfish soever man may be supposed, there are evidently some principles in his nature which interest him in the fortune of others, and render their happiness necessary to him.     

Genetic and environmental influences on observed personality: evidence from the German Observational Study of Adult Twins

Previous behavior-genetic research on adult personality relied primarily on self-reports or peer reports that may be subject to contrast effects, resulting in biased estimates of genetic and environmental influences. In the German Observational Study of Adult Twins (GOSAT), personality traits of 168 monozygotic (MZ) and 132 dizygotic (DZ) twin pairs were rated on 35 adjective scales, largely markers of the Big 5. The ratings were provided by 120 judges who never met the twins but observed videotaped behaviors of 1 twin of each pair in 1 of 15 different settings. The aggregated video-based trait ratings were highly reliable, and substantial correlations were obtained between MZ as well as DZ twins. Model-fit analyses suggested about 40% genetic, 25% shared environmental, and 35% nonshared environmental influence. Extraversion was the only trait that seemed not to be influenced by shared environment.     

Intolerance to delayed reward in girls with multiple suicide attempts

Impulsivity has been conceptualized as influencing the expression of suicidal behavior. Adolescence is a developmental period characterized both by a relatively high rate of suicide attempts and a high level of impulsivity. The current study examined two behavioral measures (delay reward and disinhibition) and one self-report measure of impulsivity among girls with suicide attempt histories. Girls with multiple suicide attempts performed more impulsively on measures of delayed reward, and had higher self-ratings of depression and aggression than girls with either one or no suicide attempts. The multiple attempter girls' preference for immediate gratification may directly increase vulnerability to suicidal acts in the context of distressing states or indirectly increase risk by creating poor life experience over time.