This study investigated the influences of neighborhood factors (residential stability and neighborhood disadvantage) and variants of the serotonin transporter linked polymorphic region (5-HTTLPR) genotype on the development of substance use among African American children aged 10–24 years. To accomplish this, a harmonized data set of five longitudinal studies was created via pooling overlapping age cohorts to establish a database with 2,689 children and 12,474 data points to span ages 10–24 years. A description of steps used in the development of the harmonized data set is provided, including how issues such as the measurement equivalence of constructs were addressed. A sequence of multilevel models was specified to evaluate Gene × Environment effects on growth of substance use across time. Findings indicated that residential instability was associated with higher levels and a steeper gradient of growth in substance use across time. The inclusion of the 5-HTTLPR genotype provided greater precision to the relationships in that higher residential instability, in conjunction with the risk variant of 5-HTTLPR (i.e., the short allele), was associated with the highest level and steepest gradient of growth in substance use across ages 10–24 years. The findings demonstrated how the creation of a harmonized data set increased statistical power to test Gene × Environment interactions for an under studied sample.

This study was designed to examine the prospective relations of life stress and genetic status with increases in drug use. African Americans (N = 399) in rural Georgia (Wave 1 mean age = 17 years) provided three waves of data across 27.5 months and a saliva sample from which the dopamine receptor D4 (DRD4) gene was genotyped. Multilevel growth curve modeling analysis indicated that emerging adults manifested the highest escalations in drug use when they reported high life stress and carried an allele of DRD4 with 7 or more repeats (7 + R allele). In addition, emerging adults who reported high life stress and carried the 7 + R allele evinced the largest increases in two proximal risk factors for drug use: affiliations with drug-using companions and drug use vulnerability cognitions. Furthermore, when the Gene × Environment interaction effects on the increases in affiliations with drug-using companions and vulnerability cognitions were entered into the model forecasting drug use, the Life Stress × DRD4 Status interaction on drug use became nonsignificant in the presence of the risk mechanisms. This finding provides an example of “second generation” Gene × Environment interaction research in which the interaction's effects on proximal risk mechanisms account for its effects on outcomes.

A retrospective longitudinal research design was used to evaluate male adult outcomes associated with four patterns of physical aggression from childhood to adulthood—child-only aggression, child and adult continuity of aggression, adult-onset aggression, and a contrast group with low levels of aggression in childhood and adulthood. The continuity and adult-onset aggression groups had the highest levels of social maladjustment (e.g., marital instability), psychiatric disturbance (e.g., alcohol disorders, major depression), personality dysfunction (e.g., higher prevalence of elevated borderline and narcissistic personality disorder scores), and higher plasma testosterone levels. The child-only aggression group manifested more psychiatric and personality disturbance than the contrast group, but not nearly as much disturbance as the continuity and adult-onset groups. After controlling for age and socioeconomic status (SES) variables, race (White/Black) was typically not a significant predictor of outcome variables. Findings are discussed with regard to life course implications of the physical aggression patterns, and of the support provided for an adult-onset aggressive type.

Data from a community-based sample of 1,126 10th- and 11th-grade adolescents were analyzed using a model-based cluster analysis approach to empirically identify heterogeneous adolescent subpopulations from the person-oriented and pattern-oriented perspectives. The model-based cluster analysis is a new clustering procedure to investigate population heterogeneity utilizing finite mixture multivariate normal densities and accordingly to classify subpopulations using more rigorous statistical procedures for the comparison of alternative models. Four cluster groups were identified and labeled multiproblem high-risk, smoking high-risk, normative, and low-risk groups. The multiproblem high risk exhibited a constellation of high levels of problem behaviors, including delinquent and sexual behaviors, multiple illicit substance use, and depressive symptoms at age 16. They had risky temperamental attributes and lower academic functioning and educational expectations at age 15.5 and, subsequently, at age 24 completed fewer years of education, and reported lower levels of physical health and higher levels of continued involvement in substance use and abuse. The smoking high-risk group was also found to be at risk for poorer functioning in young adulthood, compared to the low-risk group. The normative and the low risk groups were, by and large, similar in their adolescent and young adult functioning. The continuity and comorbidity path from middle adolescence to young adulthood may be aided and abetted by chronic as well as episodic substance use by adolescents.

Semiparametric group-based mixture modeling was used with data from an adolescent school sample (N = 1205) for three purposes. First, five trajectory groups were identified to characterize different patterns of change in the frequency of marijuana use across four waves of assessment during adolescence. These trajectory groups were labeled Abstainers, Experimental Users, Decreasers, Increasers, and High Chronics. Second, trajectory group comparisons were made across eight adolescent risk factors to determine distinctive predictors of the trajectory groups. Findings indicated, for example, that the High Chronic group, relative to the other trajectory groups, had higher levels of delinquency, lower academic performance, more drug using friends, and more stressful life events. Third, adolescent trajectory group comparisons were made across 10 risk behaviors in young adulthood (average subject age = 23.5 years) and the occurrence of psychiatric and substance abuse disorders. Findings indicated some consistency across adolescence to young adulthood with regard to risk factors, and specificity with regard to the prediction of disorders. Adolescent trajectory group membership was significantly associated in young adulthood with cannabis and alcohol disorders but not with major depressive disorders or anxiety disorders.This research was supported by a grant (R37-AA07861) awarded to Michael Windle from the National Institute on Alcohol Abuse and Alcoholism. An earlier version of this article was presented at the Michigan Symposium on Development and Psychopathology: Continuity and Discontinuity during the Transition to Adulthood, Ann Arbor, MI, June 14–15, 2002.

In traditional models of P diffusion in Si, vacancy assisted diffusion mechanism has been assumed. More recently, experiments have determined that for intrinsic P diffusion in Si, the interstitial assisted diffusion mechanism dominates. We have performed ab-initio pseudopotential calculations to study P diffusion in Si. Special care is taken with regard to structure minimization, charge state effects and corrections. We calculated the defect formation energies and migration barriers for the various competing P-interstitial complex diffusion mechanisms for low concentration P region, as well as the energetics of different charge states P-vacancy complex diffusion. For interstitial mediated diffusion of P-Sii pair in Si, we find the overall diffusion activation energies calculated are 3.1 eV for neutral case, and 3.4 eV for +1 charge case. This is in agreement with experimental observation that the interstitial mechanism dominates for intrinsic P diffusion in Si. For vacancy mediated diffusion, our calculations are in agreement with previous calculations result in the neutral case. We obtained the lower bounds for diffusion activation energy of 3.8 eV for (PV)0 and 3.4 eV for (PV). A further evaluation of the numbers would require a proper treatment of the energy states in the band-gap due to Jahn-Teller relaxations.

This study of over 1,000 adolescents focused on common and distinctive correlates of foursubgroups—no problem, depressed only, heavy drinking only, and mixed (depressed andheavy drinking). Correlates were evaluated from the domains of personal dispositions (e.g.,temperament), interpersonal relations (e.g., parent and peer), stressful life events, and otherproblem behaviors (e.g., delinquency, substance use). The no-problem subgroup differed fromthe other three subgroups in the direction of healthier functioning on almost all measures. Themixed subgroup reported the most pervasive, low levels of functioning, with the highest levels ofchildhood externalizing problems and stressful life events, the lowest levels of family socialsupport, and high levels of delinquency and substance use. The depressed-only subgroup reporteda more internalized pattern characterized by childhood avoidance problems, a difficulttemperament (e.g., inflexibility, withdrawal, low task orientation), interpersonal stressors, andpoor coping strategies. The heavy-drinking-only subgroup was characterized by higher drinkinglevels by primary caregivers and lower levels of family cohesion as reported by primarycaregivers. The 1-year prospective findings were generally consistent with the concurrentfindings in that variables that were associated with transitions toward and away from depressionand heavy drinking were associated with specific transitions (e.g., childhood externalizingproblems were associated with the transition from no problem to heavy drinking).