Amy J. Mikolajewski

An examination of environmental and genetic contributions to the determinants of suicidal behavior among male twins

The purpose of the present study was to examine the relative association of genetic and environmental factors with individual differences in each of the proximal, jointly necessary, and sufficient causes for suicidal behavior, according to the Interpersonal-Psychological Theory of Suicide (IPTS; Joiner, 2005). We examined data on derived scales measuring acquired capability, belongingness, and burdensomeness (the determinants of suicidal behavior, according to theory) from 348 adolescent male twins. Univariate biometrical models were used to estimate the magnitude of additive genetic (A), non-additive genetic (D), shared environmental (C), and non-shared environmental (E) effects associated with the variance in acquired capability, belongingness, and burdensomeness. The best fitting model for the acquired capability allowed for additive genetic and environmental effects, whereas the best fitting model for burdensomeness and belongingness allowed for shared and non-shared environmental effects. The present research extends prior work by specifying the environmental and genetic contributions to the components of the IPTS, and our findings suggest that belongingness and burdensomeness may be more appropriate targets for clinical intervention than acquired capability as these factors may be more malleable or amenable to change.

Do aggression and rule-breaking have different interpersonal correlates? A study of antisocial behavior subtypes, negative affect, and hostile perceptions of others.

There is mounting evidence that physical aggression and nonaggressive, rule-breaking delinquency constitute two separable though correlated subtypes of antisocial behavior. Even so, it remains unclear whether these behavioral subtypes have meaningfully different interpersonal correlates, particularly as they are subsumed within the same broad domain of antisocial behavior. To evaluate this, we examined whether hostile perceptions of others (assessed via exposure to a series of neutral unknown faces) were linked to level and type of antisocial behavior aggression vs. rule-breaking, and moreover, whether this association persisted even when also considering the common association with negative affect (as manipulated via written recollection of ones best and worst life experiences). Analyses revealed that aggression, but not rule-breaking, was uniquely tied to hostile perceptions of others. Furthermore, this association persisted over and above the common association of both hostile perceptions and aggression with negative affect (at both trait and state levels). Such results provide additional support for clinically meaningful differences between the behavioral subtypes of aggression and nonaggressive rule-breaking and for the independent role of hostile perceptions in aggressive behavior.

Negative Affect Shares Genetic and Environmental Influences with Symptoms of Childhood Internalizing and Externalizing Disorders.

The co-occurrence of internalizing and externalizing disorders suggests that they may have common underlying vulnerability factors. Research has shown that negative affect is moderately positively correlated with both internalizing and externalizing disorders in children. The present study is the first to provide an examination of negative affect in relation to a wide spectrum of childhood internalizing and externalizing problems using a biometric model. This study extends prior findings of more narrowly focused associations by using a factor approach including multiple disorders. The sample for this study included families of 691 same-sex 7- to 13-year old twin pairs. A multifactorial independent pathway model was used to examine the genetic and environmental influences underlying the covariation of parent-reported negative affect, internalizing symptoms, and externalizing symptoms. Results of the current study suggest that negative affect shares genetic and environmental influences with both internalizing and externalizing disorders in childhood. These common influences may partially explain their comorbidity. Understanding that negative affect is at least one contributor to the covariation among these disorders may highlight avenues for early risk assessment, intervention, and perhaps prevention.

An Update on the Florida State Twin Registry

The Florida State Twin Registry began in 2002 through a pilot study of personality disorders and executive cognitive functioning in adult twins. Since 2006, the registry has grown substantially as part of the Learning Disability Research Center at Florida State University that recently began its second funding cycle through the National Institute of Child Health and Development. An update on the Florida State Twin Registry sample, focus, and measures is provided, as well as future directions.

Common genetic and nonshared environmental factors contribute to the association between socioemotional dispositions and the externalizing factor in children.

BACKGROUND Childhood behavioral disorders including conduct disorder (CD), oppositional defiant disorder (ODD), and attention-deficit/hyperactivity disorder (ADHD) often co-occur. Prior twin research shows that common sets of genetic and environmental factors are associated with these various disorders and they form a latent factor called Externalizing. The developmental propensity model posits that CD develops in part from socioemotional dispositions of prosociality, negative emotionality, and daring; and recent research has supported the expected genetic and environmental associations between these dispositions and CD. This study examined the developmental propensity model in relation to the broader Externalizing factor that represents the covariance among behavior disorders in children. METHODS Parents of 686 six- to twelve-year-old twin pairs rated them on symptoms of CD, ADHD, and ODD using the disruptive behavior disorder scale and on prosociality, negative emotionality, and daring using the child and adolescent dispositions scale. A latent factor multivariate Cholesky model was used with each disposition latent factor comprised of respective questionnaire items and the Externalizing factor comprised of symptom dimensions of CD, ADHD inattention, ADHD hyperactivity/impulsivity, and ODD. RESULTS Results supported the hypothesis that the socioemotional dispositions and the Externalizing factor have genetic factors in common, but there was not a single genetic factor associated with all of the constructs. As expected, nonshared environment factors were shared by the dispositions and externalizing factor but, again, no single nonshared environmental factor was common to all constructs. A shared environmental factor was associated with both negative emotionality and externalizing. CONCLUSIONS The developmental propensity model was supported and appears to extend to the broader externalizing spectrum of childhood disorders. Socioemotional dispositions of prosociality, negative emotionality, and (to a lesser extent) daring may contribute to the covariation among behavioral disorders and perhaps to their comorbid expression through common sets of primarily genetic but also environmental factors.

The association between affective psychopathic traits, time incarcerated, and cortisol response to psychosocial stress.

Previous research has demonstrated that psychopathic personality traits are significantly predictive of blunted cortisol reactivity to a performance-based stressor task (Trier Social Stress Test; TSST) in college students. However, the relationship between cortisol reactivity and psychopathy has not been explored in high risk samples such as incarcerated populations. Further, the role of imprisonment in relation to cortisol stress reactivity has not been previously explored, but could have practical and conceptual consequences in regard to rehabilitation and biological sensitivity to context, respectively. The current study tested the hypotheses that both psychopathic personality traits and amount of time incarcerated are related to cortisol blunting in response to stress among incarcerated young adults. A sample of 49 young adult male offenders was recruited to complete the TSST. Salivary hormone samples were taken just prior to and 20 min post-stressor, and participants were interviewed with the Psychopathy Checklist-Youth Version. Variables quantifying the amount of time at the present facility prior to the date of testing and number of commitments in juvenile facilities were also collected. Correlational analyses indicated that only number of incarcerations was related to blunted cortisol. Hierarchical Linear Modeling revealed that time incarcerated and number of commitments were related to a blunted cortisol response among responders and declining cortisol reactivity among nonresponders, respectively. Controlling for time incarcerated, psychopathic traits were significantly related to cortisol decline in response to the stressor among nonresponders, but were not related to blunted cortisol among responders. Results of this project highlight the potential biological effects of prolonged and repeated incarcerations, and extend our understanding about the relationship between psychopathic traits and cortisol reactivity in an incarcerated sample.

Examining the factor structure and etiology of prosociality.

Prosociality is one construct included in the developmental propensity model proposed by Lahey and Waldman (2003, 2005) to explain the development of conduct problems in childhood and adolescence. Findings from previous literature on 2 facets of prosociality, dispositional sympathy and respect for rules, suggest that both may have genetic and nonshared environmental influences, but only the latter may have shared environmental influence. The goal of the current article was to explore the structure of the prosociality disposition from a measurement perspective as well as to examine the etiology of this construct. The sample consisted of 686 twin pairs ages 7 to 13. Parents rated their childrens prosociality using the Child and Adolescent Dispositions Scale. The factor structure of the prosociality scale was examined using confirmatory factor analysis to compare a 1-factor model with a 2-factor model. Twin analyses were used to examine the proportion of variance associated with genetic and environmental effects on the latent factor(s) from the best fitting model. Results of the current study suggest that prosociality is a disposition that can be conceptualized as 2 related factors rather than a unitary dimension. These 2 factors map onto the subscales of the prosociality dimension (dispositional sympathy and respect for rules). Both factors had significant genetic and nonshared environmental influences, but only respect for rules had significant shared environmental influences. Examining the dispositional sympathy and respect for rules facets of prosociality separately allowed for the discovery that shared environmental factors may have more impact on respect for rules than sympathy.

Home environmental and behavioral risk indices for reading achievement

The goal of this study was to identify home environmental and temperament/behavior variables that best predict standardized reading comprehension scores among school-aged children. Data from 269 children aged 9-16 (M = 12.08; SD = 1.62) were used in discriminant function analyses to create the Home and Behavior indices. Family income was controlled in each index. The final Home and Behavior models each classified around 75% of cases correctly (reading comprehension at grade level vs. not). Each index was then used to predict other outcomes related to reading. Results showed that Home and/or Behavior accounted for 4-7% of the variance in reading fluency and spelling and 20-35% of the variance in parent-rated problems in math, social anxiety, and other dimensions. These metrics show promise as environmental and temperament/behavior risk scores that could be used to predict and potentially screen for further assessment of reading related problems.