Genetic and environmental influences on cortisol reactivity to a psychosocial stressor in adolescents and young adults.

Individuals vary in their response to psychological and physiological stressors, and this reactivity can be captured using measures of cortisol. Previous research suggests cortisol reactivity is under some degree of genetic control; however, the measures used have varied widely. This study (N = 524) examined potential differences in heritability across varying cortisol metrics of stress reactivity following the Trier Social Stress Test (TSST) and whether these measures are genetically or environmentally interrelated. Participants included twins aged 15-20 years (56% female). Cortisol reactivity to the TSST was assessed via serial salivary cortisol samples collected pre- and post-TSST. Modest to moderate heritability estimates (12% [95CI: 1-36%] - 45% [95CI: 16-69%]) were observed across measures purported to capture stress reactivity (peak, area under the curve [AUC], baseline-to-peak change). Findings also demonstrate both shared and unique genetic and environmental influences between baseline cortisol and cortisol reactivity. Minimal to no additional genetic innovations above and beyond the contributions of peak cortisol were found for other measures of cortisol reactivity such as AUC. This study is one of the largest twin-based samples to examine the heritability of cortisol reactivity, and results suggest that simpler measures of cortisol reactivity demonstrate higher heritability compared to more complex measurements.

Confirmatory factor structure and psychometric properties of the Multidimensional Peer Victimization Scale.

The Multidimensional Peer Victimization Scale (MPVS; Mynard & Joseph, 2000) is a 16-item self-report scale that captures peer victimization across four dimensions: physical victimization, verbal victimization, social manipulation, and attacks on property. Performance of the scale has not been evaluated among older adolescents. We examined the factor structure, internal consistency reliability, and performance of the scale in two separate epidemiological U.S. samples representing different age groups: 9-14 year olds (N=610) and 15-17 year olds (N=524). The four-factor structure of the scale was affirmed in both samples, however; there was not metric invariance by gender in the younger age group. The scale and its subscales were found to have good internal consistency. Expected relationships between the MPVS and measures of irritability, anxiety, and depression were affirmed. Results support continued use of the MPVS among child and adolescent samples.

Age-Related Differences in the Structure of Genetic and Environmental Contributions to Types of Peer Victimization.

The goal of the present investigation was to clarify and compare the structure of genetic and environmental influences on different types (e.g., physical, verbal) of peer victimization experienced by youth in pre-/early adolescence and mid-/late adolescence. Physical, verbal, social, and property-related peer victimization experiences were assessed in two twin samples (306 pairs, ages 9-14 and 294 pairs, ages 15-20). Cholesky decompositions of individual differences in victimization were conducted, and independent pathway (IP) and common pathway (CP) twin models were tested in each sample. In the younger sample, a Cholesky decomposition best described the structure of genetic and environmental contributors to peer victimization, with no evidence that common additive genetic or environmental factors influence different types of peer victimization. In the older sample, common environmental factors influenced peer victimization types via a general latent liability for peer victimization (i.e., a CP model). Whereas the pre-/early adolescent sample demonstrated no evidence of a shared genetic and environmental structure for different types of peer victimization, the mid-/late adolescent sample demonstrates the emergence of an environmentally-driven latent liability for peer victimization across peer victimization types.

Resting Heart Rate Variability (HRV) in Adolescents and Young Adults from a Genetically-Informed Perspective.

Reduced heart rate variability (HRV) is associated with cardiac morbidity, mortality, and negative psychopathology. Most research concerning genetic influences on HRV has focused on adult populations, with fewer studies investigating the developmental period of adolescence and emerging adulthood. The current study estimated the genetic and environmental contributions to resting HRV in a sample of twins using various HRV time domain metrics to assess autonomic function across two different time measurement intervals (2.5- and 10-min). Five metrics of resting HRV [mean interbeat interval (IBI), the standard deviation of normal IBIs (SDNN), root square mean of successive differences between IBIs (RMSSD), cardiac vagal index (CVI), and cardiac sympathetic index (CSI)] were assessed in 421 twin pairs aged 14-20 during a baseline electrocardiogram. This was done for four successive 2.5-min intervals as well as the overall 10-min interval. Heritability (h2) appeared consistent across intervals within each metric with the following estimates (collapsed across time intervals): mean IBI (h2 = 0.36-0.46), SDNN (h2 = 0.23-0.30), RMSSD (h2 = 0.36-0.39), CVI (h2 = 0.37-0.42), CSI (h2 = 0.33-0.46). Beyond additive genetic contributions, unique environment also was an important influence on HRV. Within each metric, a multivariate Cholesky decomposition further revealed evidence of genetic stability across the four successive 2.5-min intervals. The same models showed evidence for both genetic and environmental stability with some environmental attenuation and innovation. All measures of HRV were moderately heritable across time, with further analyses revealing consistent patterns of genetic and environmental influences over time. This study confirms that in an adolescent sample, the time interval used (2.5- vs. 10-min) to measure HRV time domain metrics does not affect the relative proportions of genetic and environmental influences.

Profiles of internalizing and externalizing symptoms associated with bullying victimization.

This study identified profiles of internalizing (anxiety and depression) and externalizing (delinquency and violence against peers) symptoms among bullying victims and examined associations between bullying victimization characteristics and profile membership. The sample consisted of 1196 bullying victims in grades 8-10 (Mage = 14.4, SD = 1.01) who participated in The Context Study in three North Carolina counties in Fall 2003. Five profiles were identified using latent profile analysis: an asymptomatic profile and four profiles capturing combinations of internalizing and externalizing symptoms. Associations between bullying characteristics and membership in symptom profiles were tested using multinomial logistic regression. More frequent victimization increased odds of membership in the two high internalizing profiles compared to the asymptomatic profile. Across all multinomial logistic regression models, when the high internalizing, high externalizing profile was the reference category, adolescents who received any type of bullying (direct, indirect, or dual) were more likely to be in this category than any others.

Examining explanations for the link between bullying perpetration and physical dating violence perpetration: Do they vary by bullying victimization?

This short-term longitudinal study examined whether the association between bullying perpetration and later physical dating violence perpetration and mediators of that association (via anger, depression, anxiety, and social status), varied depending on level of bullying victimization. Differences have been noted between those who bully but are not victims of bullying, and those who are both bullies and victims. These differences may influence dating violence risk and the explanations for why bullying leads to dating violence. Data were from dating adolescents in three rural counties who completed self-administered questionnaires in the fall semester of grades 8-10 and again in the spring semester. The sample (N = 2,414) was 44.08% male and 61.31% white. Bullying perpetration in the fall semester predicted physical dating violence perpetration in the spring semester when there was no bullying victimization, but not when there was any bullying victimization. Bullying perpetration was positively associated with anger at all levels of bullying victimization and with social status when there was no or low amounts of victimization; it was negatively associated with social status at high levels of victimization. Bullying victimization was positively associated with anger, depression, and anxiety at all levels of bullying perpetration. Anger mediated the association between bullying perpetration and dating violence, regardless of level of victimization; depression, anxiety, and social status did not mediate the association at any level of bullying victimization. The findings have implications for dating violence prevention efforts and for future research on the link between bullying and dating violence.

Changing trends of HIV-related hospitalizations: a small area analysis in Illinois, 1994-2000.

This paper describes the characteristics of HIV-related hospitalizations in Illinois and compares these to nationally available data. We used HIV-related hospitalization data abstracted from an administrative dataset maintained by state mandate. Overall, HIV-related hospitalizations decreased in Illinois between 1996 and 2000. The proportion of hospitalizations for infants also decreased. However, trend analyses indicated that both the proportion of hospitalizations involving females and the mean age of hospitalized patients increased while the proportion of hospitalizations ending in mortality and the average charge per hospitalization decreased during the observation period. Small area analyses found significant regional variations in the proportion of hospitalizations ending in in-hospital mortality, costs of a hospitalization and rate of decline in the percent of hospitalization over time. Compared to national data, HIV-related hospitalizations in Illinois were more expensive, less likely to end in mortality and less likely to involve females. These results indicate that evaluation of data at several geographic levels can provide healthcare policy makers with essential information at each level of analysis.