Genetic and environmental determination of tracking in static strength during adolescence.
(9/524)
The purpose of this study was to determine whether the observed phenotypic stability in static strength during adolescence, as measured by interage correlations in arm pull, is mainly caused by genetic and/or environmental factors. Subjects were from the Leuven Longitudinal Twin Study (n = 105 pairs, equally divided over 5 zygosity groups). Arm-pull data were aligned on age at peak height velocity to attenuate the temporal fluctuations in interage correlations caused by differences in timing of the adolescent growth spurt. Developmental genetic models were fitted using structural equation modeling. After the data were aligned on age at peak height velocity, the annual interage correlations conformed to a quasi-simplex structure over a 4-yr interval. The best-fitting models included additive genetic and unique environmental sources of variation. Additive genetic factors that already explained a significant amount of variation at previous measurement occasions explained 44.3 and 22.5% of the total variation at the last measurement occasion in boys and girls, respectively. Corresponding values for unique environmental sources of variance are 31.2 and 44.5%, respectively. In conclusion, the observed stability of static strength during adolescence is caused by both stable genetic influences and stable unique environmental influences in boys and girls. Additive genetic factors seem to be the most important source of stability in boys, whereas unique environmental factors appear to be more predominant in girls. (+info)
Peer relationship antecedents of delinquent behavior in late adolescence: is there evidence of demographic group differences in developmental processes?
(10/524)
A longitudinal prospective design was used to test the generalizability of low levels of social preference and high levels of antisocial peer involvement as risk factors for delinquent behavior problems to African American (AA) and European American (EA) boys and girls (N = 384). Social preference scores were computed from peer reports in middle childhood (ages 6-9). Parents and adolescents reported antisocial peer involvement in early adolescence (ages 13-16) and adolescents reported on their own delinquent behavior in late adolescence (ages 17 and 18). Analyses tested for differences across four groups (AA boys, EA boys, AA girls, EA girls) in construct measurement, mean levels, and associations among variables. Few measurement differences were found. Mean-level differences were found for social preference and delinquent behavior. AA boys were least accepted by peers and reported the highest level of delinquent behavior. EA girls were most accepted by peers and reported the lowest level of delinquent behavior. Associations among peer experiences and delinquent behavior were equivalent across groups, with lower levels of social preference and higher levels of antisocial peer involvement associated with more delinquent behavior. Person-centered analyses showed the risk associated with low social preference and high antisocial peer involvement to be similar across groups, providing further evidence of the generalizability of the peer relationship experiences as risk factors for subsequent delinquent behavior problems. (+info)
Developmental trajectories of offending: validation and prediction to young adult alcohol use, drug use, and depressive symptoms.
(11/524)
This longitudinal study extended previous work of Wiesner and Capaldi by examining the validity of differing offending pathways and the prediction from the pathways to substance use and depressive symptoms for 204 young men. Findings from this study indicated good external validity of the offending trajectories. Further, substance use and depressive symptoms in young adulthood (i.e., ages 23-24 through 25-26 years) varied depending on different trajectories of offending from early adolescence to young adulthood (i.e., ages 12-13 through 23-24 years), even after controlling for antisocial propensity, parental criminality, demographic factors, and prior levels of each outcome. Specifically, chronic high-level offenders had higher levels of depressive symptoms and engaged more often in drug use compared with very rare, decreasing low-level, and decreasing high-level offenders. Chronic low-level offenders, in contrast, displayed fewer systematic differences compared with the two decreasing offender groups and the chronic high-level offenders. The findings supported the contention that varying courses of offending may have plausible causal effects on young adult outcomes beyond the effects of an underlying propensity for crime. (+info)
The association between diet and height in the postinfancy period changes with age and socioeconomic status in Filipino youths.
(12/524)
Whether the determinants of linear growth can have independent effects beyond the critical infancy period has been questioned. This research uses uniquely suited data from >2000 youths from the Cebu Longitudinal Health and Nutrition Study in the Philippines to examine the association between diet and height in the postinfancy period. Anthropometric, diet, and other data were collected bimonthly from 0 to 2 y, and at the mean ages of 8, 11.5, 15.5, and 18.5 y. Generalized Estimating Equations were used to quantify the mean effects of diet diversity and energy intake on height across increments demarcated by the postinfancy data (2-8.5, 8.5-11.5, 11.5-15.5, and 15.5-18.5 y). We examined whether the effects differed by socioeconomic status (SES) and age. Effects with P < 0.05 were considered significant. Each additional unit of diet variety (range 0-8 U) was associated with a significant 0.33-cm increase in height in boys. Each additional 100 kcal (4186 kJ) was associated with significant increases in height of 0.05 cm in boys, and 0.02 cm in girls. Significant interactions (P < 0.15) with SES showed that each 100 kcal increase in energy intake was associated with a 0.08-cm increase in height at low SES with no difference at high SES. In both boys and girls, the effects of energy intake decreased with age, as shown by a significant age interaction (P < 0.15). The methods used incorporate the longitudinal nature of the data to offer a unique examination of the association between diet and height in the postinfancy period. (+info)
Child and adolescent growth disorders--an overview.
(13/524)
BACKGROUND: While many children presenting with apparent disorders of growth will be short or tall children growing normally, it is important to identify those children who have an underlying pathological cause. Parental expectation and anxiety will often accompany growth issues and this needs to be addressed. OBJECTIVE: The article aims to assist the clinician in distinguishing pathological short stature from normal variants, and to guide in the management of normal variants and common pathologies. DISCUSSION: Pathological short stature can be distinguished from normal variants by careful history and examination followed by accurate assessment of the growth parameters of height, weight, body proportions and growth velocity, and judicious use of investigations. Growth is a dynamic process that requires multiple measurements over time. If the patient has a nonpathological cause of short stature, explanation and reassurance are critical--for both the parents and child--to feel supported and comfortable with their height outcome. (+info)
Adolescent medicine in paediatric practice.
(14/524)
Adolescents are a growing area in paediatric practice in both hospital and community settings. They make up around one quarter of the practice of many paediatricians. Yet until recently there has been little formal interest in young people's health in the UK. The situation is now changing, particularly following the publication of the "National Service Framework for children, young people and maternity services", which places a major emphasis on adolescent health. Given that this area is relatively new to many paediatricians, this article aims to provide an overview of the range of health problems that affect young people, to provide practical advice for working with this group in paediatric practice, and to outline current and future opportunities for training in adolescent health in the UK. (+info)
Development of the interval endurance capacity in elite and sub-elite youth field hockey players.
(15/524)
OBJECTIVES: To gain more insight into the mechanisms that underlie the development of interval endurance capacity in talented youth field hockey players in the 12-19 age band. METHODS: A total of 377 measurements were taken over three years. A longitudinal model for interval endurance capacity was developed using the multilevel modelling program MLwiN. With the model, scores on the interval shuttle run test can be predicted for elite and sub-elite male and female field hockey players aged 12-19 years. RESULTS: A polynomial model of order 2 adequately represents development of the test scores over time. The fixed part of the model contains a different intercept and linear age term for boys and girls, and a common quadratic term; the random part of the model has a common level 2 variance and sex specific level 1 variances. The model was significantly improved by including differential effects of performance level for age and sex. A negative effect was found for percentage body fat, and positive effects for additional training and motivation. CONCLUSIONS: During adolescence, both male and female elite hockey players show a more promising development pattern of interval endurance capacity than sub-elite youth players. Percentage body fat, additional training hours, and motivation influence this development. However, differences between the individual players are still considerable. (+info)
Adolescents' behavior in the presence of interparental hostility: developmental and emotion regulatory influences.
(16/524)
Within-family covariation between interparental hostility and adolescent behavior across three interactions over a 2-year period was explored in a sample that included 37 typical adolescents and 35 adolescents recently hospitalized for psychiatric difficulties. More interparental hostility across the three interactions was associated with more adolescent hostility and more positive engagement (at a trend level) regardless of psychiatric background. Parent-to-child hostility in each interaction mediated the link for adolescent hostility but not for positive adolescent engagement. Emotion regulation capacities and age were linked to variability in adolescents' behavior in the presence of interparental conflict. In interactions with more interparental hostility, adolescents with greater capacity to tolerate negative affect were more likely to show increased positive engagement, and adolescents who were better able to modulate their emotional expression were less likely to show increased hostility. Covariation between interparental and adolescent hostility across the three family interactions decreased as the adolescent aged. These findings are consistent with the theory that exposure to interparental hostility is emotionally disequilibrating, and that adolescent responses may reflect differences in emotion regulation and other developmentally based capacities. Gender and variations across families in overall levels of hostile parenting were also linked with adolescent behavior in the presence of interparental hostility. (+info)