Genetic and environmental influences on pubertal development: longitudinal data from Finnish twins at ages 11 and 14

The onset of pubertal development and actigraphy-assessed sleep during middle childhood: Racial, gender, and genetic effects

OBJECTIVE

This study (1) examined pubertal development in relation to actigraphy-assessed sleep in twin children, and tested whether associations differed by child race and gender, (2) modeled genetic and environmental influences on pubertal development and sleep indicators, and (3) examined genetic and environmental influences on the covariation of puberty and sleep.

DESIGN

The classic twin design was used to examine genetic and environmental contributions to puberty and sleep and their associations.

SETTING

Data were collected from community-dwelling urban and rural families of twins in the southwestern U.S.

PARTICIPANTS

The racially and socioeconomically diverse sample included 596 twin children (M_age = 8.41, SD = 0.69; 51.7% female; 66.3% white; 33.7% Hispanic; 170 monozygotic, 236 same-sex dizygotic, 188 opposite-sex dizygotic).

MEASUREMENTS

Pubertal development was assessed via parent report. Children wore actigraph watches for 7 nights (M = 6.81, SD = 0.67) to capture sleep duration, efficiency, midpoint, onset latency, and duration variability.

RESULTS

In contrast to extant literature with older youth, more advanced pubertal development was associated with longer sleep durations in Hispanic and white girls and higher sleep efficiency in white girls, though Hispanic girls demonstrated later sleep midpoints. Pubertal development was moderately heritable and there was a genetic influence on the covariance between puberty and sleep indicators.

CONCLUSIONS

This was the first study to examine the genetic and environmental influences on the covariation between puberty and sleep, and found genetic underpinnings between pubertal development and actigraphy-assessed sleep duration and efficiency, though sleep and puberty were almost entirely independent in twins at this age.

Genetic and Epigenetic Control of Puberty

Puberty is a complex transitional phase in which reproductive capacity is achieved. There is a very wide variation in the age range of the onset of puberty, which follows a familial, ethnic, and sex pattern. The hypothalamic-pituitary-gonadal axis and several genetic, environmental, and nutritional factors play an important role in the onset of and throughout puberty. Recently, there has been significant progress in identifying factors that affect normal pubertal timing. Different studies have identified single nucleotide polymorphisms (SNPs) that affect pubertal timing in both sexes and across ethnic groups. Single genes are implicated in both precocious and delayed puberty, and epigenetic mechanisms have been suggested to affect the development and function of the GnRH neuronal network and responsiveness of end organs. All these factors can influence normal puberty timing, precocious puberty, and delayed puberty. The objective of this review is to describe recent findings related to the genetic and epigenetic control of puberty and highlight the need to deepen the knowledge of the regulatory mechanisms of this process in the normal and abnormal context.

Neurobiology of puberty and its disorders

Puberty, which in humans is considered to include both gonadarche and adrenarche, is the period of becoming capable of reproducing sexually and is recognized by maturation of the gonads and development of secondary sex characteristics. Gonadarche referring to growth and maturation of the gonads is fundamental to puberty since it encompasses increased gonadal steroid secretion and initiation of gametogenesis resulting from enhanced pituitary gonadotropin secretion, triggered in turn by robust pulsatile GnRH release from the hypothalamus. This chapter reviews the development of GnRH pulsatility from before birth until the onset of puberty. In humans, GnRH pulse generation is restrained during childhood and juvenile development. This prepubertal hiatus in hypothalamic activity is considered to result from a neurobiological brake imposed upon the GnRH pulse generator resident in the infundibular nucleus. Reactivation of the GnRH pulse generator initiates pubertal development. Current understanding of the genetics and physiology of the brake will be discussed, as will hypotheses proposed to account for timing the resurgence in pulsatile GnRH and initiation of puberty. The chapter ends with a discussion of disorders associated with precocious or delayed puberty with a focus on those with etiologies attributed to aberrant GnRH neuron anatomy or function. A pediatric approach to patients with pubertal disorders is provided and contemporary treatments for both precocious and delayed puberty outlined.

Common Genetic Influences on Age at Pubertal Voice Change and BMI in Male Twins

The present study aimed to explore secular trends in age at voice change (AVC), estimate heritability of AVC and investigate to what extent common genes influence the association between AVC and body mass index (BMI) in South Korean males. The sample of 955 male twins consisted of 241 pairs and 118 co-twin missing monozygotic (MZ) twins, 82 pairs and 50 co-twin missing dizygotic (DZ) twins and 141 male members of opposite-sex DZ twins who participated in telephone surveys in the South Korean Twin Registry. AVC was asked of twins during the surveys. The mean (SD) age of the sample was 18.92 (2.42) years (range: 16.00-29.25 years). The birth years of the twins were divided into two groups (1988-1993, 1994-2001). Kaplan-Meyer survival analyses were conducted to compute the mean age of AVC in the total sample as well as to test mean differences between the two birth cohorts. Maximum likelihood twin correlations and univariate and bivariate model-fitting analyses were performed. The mean AVC in the total sample was 14.19 (95% CI [14.09, 14.29]) years. The mean AVC significantly declined from 14.38 to 14.02 years from 1988 to 2001, confirming downward trends in AVC in recent years. Heritability for AVC was .59 (95% CI [.50, .67]), which was within the range reported in most Western twin studies. Although the phenotypic correlation between AVC and BMI was modest (r = -.14; 95% CI [-.07, -.21]), it was entirely mediated by common genes, similar to what has been found in females in prior twin studies. In conclusion, the present twin study underscores the importance of genetic influences on pubertal timing and its association with BMI in South Korean males.

Adapted version of the Pubertal Development Scale for use in Brazil

OBJECTIVE

To determine whether scores in an adapted version of the self-assessment Pubertal Development Scale into Portuguese match those from the gold standard in pubertal development (Tanner scale).

METHODS

This was a cross-sectional study with a convenience sample of 133 children and adolescents aged nine to 17 years (59 males; mean age of 13 years and six months, with standard deviation = 25 months). Youngsters completed the Pubertal Development Scale and were then examined by specialists in adolescent medicine.

RESULTS

Exact absolute agreement of pubertal stages were modest, but significant associations between measures (correlation; intra-class correlation coefficients of consistency) showed that the Pubertal Development Scale adequately measures changes that map onto pubertal development determined by physical examination, on par with international publications. Furthermore, scores obtained from each Pubertal Development Scale question reflected adequate gonadal and adrenal events assessed by clinical ratings, mostly with medium/high effect sizes. Latent factors obtained from scores on all Pubertal Development Scale questions had excellent fit indices in Confirmatory Factor Analyses and correlated with Tanner staging.

CONCLUSIONS

We conclude that self-assessment of body changes by youngsters using the Portuguese version of the Pubertal Development Scale is useful when estimates of pubertal progression are sufficient, and exact agreement with clinical staging is not necessary. The Pubertal Development Scale is, therefore, a reliable instrument for use in large-scale studies in Brazil that aim at investigating adolescent health related to pubertal developmental. The translated version and scoring systems are provided.

Parents of early-maturing girls die younger

According to the life-history theory, rates of sexual maturation have coevolved with mortality rates so that individuals who mature faster tend to die younger. We used two data sets, providing different markers for the speed of pubertal development to test whether rates of sexual maturation of women predict the age at death of their parents. In the data set of Estonian schoolgirls born between 1936 and 1961, the rate of breast development predicted lifespan of both mothers and fathers (irrespectively of their socio-economic position), so that parents of rapidly maturing girls died at younger age. This finding supports the view that fast maturation rates in humans have coevolved with short lifespans and that such trade-offs can be detected as intergenerational phenotypic correlations in modern populations. Menarcheal age of participants of Estonian Biobank (born between 1925 and 1996) did not predict the age of death of their mothers; however, it did predict survival of their fathers, but only in environment where the genetic variation is exposed (families where at least one parent had tertiary education). In such families (where girls also matured 0.2-0.4 years earlier than in poorly educated families), 1-year delay in daughter's menarche corresponded to 9% lower hazard of father's death. Heritability of menarcheal age was also highest in well-educated families. The latter findings are consistent with the idea that genetic differences in the rate of pubertal maturation may be expressed most clearly in well-off families because in such families, the contribution of environmental variance to total phenotypic variance in menarcheal age is smallest. Our findings suggest that with global improvement and equalization of growth conditions, reductions of environmental variation in the rate of maturation increasingly expose the genetic differences in menarcheal age to selection. Under such conditions, selection on menarcheal age has a potential to affect the evolution of lifespan.

Biochemical and Molecular Bases of Lead-Induced Toxicity in Mammalian Systems and Possible Mitigations

The effects of lead exposure on mammals are reported to be devastating. Lead is present in all the abiotic environmental components such as brass, dust, plumbing fixtures, soil, water, and lead mixed imported products. Its continuous use for several industrial and domestic purposes has caused a rise in its levels, thereby posing serious threats to human health. The mechanisms involved in lead-induced toxicity primarily include free-radical-mediated generation of oxidative stress which directly imbalances the prooxidants and the antioxidants in body. The toxicity of lead involves damage primarily to major biomolecules (lipid, protein, and nucleic acids) and liver (hepatotoxicity), nervous system (neurotoxicity), kidney (nephrotoxicity) and DNA (genotoxicity), present in animals and humans. The activation of c-Jun NH2-terminal kinase, phosphoinositide 3-kinase, or Akt and p38 mitogen activated protein kinase signaling pathways are important for lead cytotoxicity. Lead increased apoptosis through signaling cascade and associated factors and significantly impairs cell differentiation and maturation. In addition, lead has great impact on metabolic pathways such as heme synthesis, thereby leading to the onset of anemia in lead exposed people. This review encompasses an updated account of varied aspects of lead-induced oxidative stress and the biomolecular consequences such as perturbations in physiological processes, apoptosis, carcinogenesis, hormonal imbalance, loss of vision, and reduced fertility and their possible remediation through synthetic (chelators) and natural compounds (plant-based principles). This paper is primarily concerned with the biomedical implications of lead-induced generation of free radical and the toxicity management in the mammalian system.

Genetic and environmental influences on pubertal hormones in human hair across development

Puberty is a complex biopsychosocial process that can affect an array of psychiatric and medical disorders emerging in adolescence. Although the pubertal process is driven by neuroendocrine changes, few quantitative genetic studies have directly measured puberty-relevant hormones. Hair samples can now be assayed for accumulation of hormones over several months. In contrast to more conventional salivary measures, hair measures are not confounded by diurnal variation or hormonal reactivity. In an ethnically and socioeconomically diverse sample of 1286 child and adolescent twins and multiples from 672 unique families, we estimated genetic and environmental influences on hair concentrations of testosterone, DHEA, and progesterone across the period of 8-18 years of age. On average, male DHEA and testosterone were highly heritable, whereas female DHEA, progesterone, and puberty were largely influenced by environmental components. We identified sex-specific developmental windows of maximal heritability in each hormone. Peak heritability for DHEA occurred at approximately 10 years of age for males and females. Peak heritability for testosterone occurred at age 12.5 and 15.2 years for males and females, respectively. Peak heritability for male progesterone occurred at 11.2 years, while the heritability of female progesterone remained uniformly low. The identification of specific developmental windows when genetic signals for hormones are maximized has critical implications for well-informed models of hormone-behavior associations in childhood and adolescence.

Early maturation and substance use across adolescence and young adulthood: A longitudinal study of Finnish twins

Early maturation, indexed by pubertal development (PD), has been associated with earlier initiation and greater frequency of adolescent substance use, but this relationship may be biased by confounding factors and effects that change across development. Using a population-based Finnish twin sample (N = 3,632 individuals), we conducted twin modeling and multilevel structural equation modeling of the relationship between PD and substance use at ages 12-22. Shared environmental factors contributed to early PD and heavier substance use for females. Biological father absence was associated with early PD for boys but not girls, and did not account for the relationship between PD and substance use. The association between early PD and heavier substance use was partially due to between-family confounds, although early PD appeared to qualitatively alter long-term trajectories for some substances (nicotine), but not others (alcohol). Mediation by peer and parental factors did not explain this relationship within families. However, higher peer substance use and lower parental monitoring were themselves associated with heavier substance use, strengthening the existing evidence for these factors as targets for prevention/intervention efforts. Early maturation was not supported as a robust determinant of alcohol use trajectories in adolescence and young adulthood, but may require longer term follow-up. Subtle effects of early PD on nicotine and illicit drug use trajectories throughout adolescence and adulthood merit further investigation.

Neighborhood Economic Deprivation and Social Fragmentation: Associations With Children's Sleep

BACKGROUND & OBJECTIVE

A growing body of work indicates that experiences of neighborhood disadvantage place children at risk for poor sleep. This study aimed to examine how both neighborhood economic deprivation (a measure of poverty) and social fragmentation (an index of instability) are associated with objective measures of the length and quality of children's sleep.

PARTICIPANTS

Participants were 210 children (54.3% boys) living predominantly in small towns and semirural communities in Alabama. On average children were 11.3 years old (SD = .63); 66.7% of the children were European American and 33.3% were African American. The sample was socioeconomically diverse with 67.9% of the participants living at or below the poverty line and 32.1% from lower-middle-class or middle-class families.

METHODS

Indicators of neighborhood characteristics were derived from the 2012 American Community Survey and composited to create two variables representing neighborhood economic deprivation and social fragmentation. Child sleep period, actual sleep minutes, and efficiency were examined using actigraphy.

RESULTS

Higher levels of neighborhood economic deprivation were associated with fewer sleep minutes and poorer sleep efficiency. More neighborhood social fragmentation was also linked with poorer sleep efficiency. Analyses controlled for demographic characteristics, child health, and family socioeconomic status.

CONCLUSIONS

Findings indicate that living in economically and socially disadvantaged neighborhoods predicts risk for shorter and lower-quality sleep in children. Examination of community context in addition to family and individual characteristics may provide a more comprehensive understanding of the factors shaping child sleep.

Transdiagnostic psychiatric disorder risk associated with early age of menarche: A latent modeling approach

BACKGROUND

Earlier age of pubertal maturation in females is associated with increased risk for mental health problems in adolescence, compared with on-time or later maturation. However, most investigations of pubertal timing and mental health consider risk for individual disorders and fail to account for comorbidity. A latent-modeling approach using a large, nationally representative sample could better explain the transdiagnostic nature of the consequences of early-onset puberty.

METHODS

Data on age of menarche and mental disorders were drawn from a population-representative sample of adolescents (n=4925), ages 13-17. Confirmatory factor analysis was used to fit four latent disorder categories: distress, eating, and externalizing, and fear disorders. Timing of menarche included those with earlier (age≤10, age 11) and later age of onset (age 13, 14+), relative to those with average timing of menarche (age 12). Associations between timing of menarche and latent disorders were estimated in a structural equation model (SEM), adjusted for age, income, race, parent marital status, BMI, and childhood adversity.

RESULTS

The measurement model evidenced acceptable fit (CFI=0.91; RMSEA=0.02). Onset of menarche before age 11 was significantly associated with distress disorders (coefficient=0.096; p<0.0001), fear disorders (coefficient=0.09; p<0.0001), and externalizing disorders (coefficient=0.039; p=0.049) as compared to on-time or late menarche. No residual associations of early menarche with individual disorders over and above the latent disorders were observed.

CONCLUSION

The latent modeling approach illuminated meaningful transdiagnostic psychiatric associations with early timing of menarche. Biological processes initiated at puberty can influence cognitive and affective processes as well as social relationships for adolescents. Under developmentally normative conditions, these changes may be adaptive. However, for those out of sync with their peers, researchers and clinicians should recognize the potential for these processes to influence liability to a broad array of psychopathological consequences in adolescence.

Heritability of serum dehydroepiandrosterone sulphate levels and pubertal development in 6∼18-year-old girls: a twin study

BACKGROUND

Dehydroepiandrosterone sulphate (DHEAS), the most plentiful circulating adrenal hormone, may be considered as a marker of the onset of adrenarche and is involved in pubertal development and metabolic disorders.

AIM

The objective of this study is to determine the genetic and environmental influences on the variation of basal DHEAS levels and pubertal development in pubertal girls.

SUBJECTS AND METHODS

Three hundred and sixty twin girls aged 6-18-years were enrolled, consisting of 132 monozygotic pairs and 48 dizygotic pairs. Anthropometric and sexual characteristics were examined. Serum DHEAS was measured by RIA. Estimates of genetic and environmental components of variance were based on the theory of normal maximum likelihood in Mx package.

RESULTS

Serum DHEAS concentrations of PH-II and PH-III were significantly higher than Tanner stage PH-I (p < .05) and maintained higher levels in PH-IV ∼ V. Heritability of serum DHEAS estimated by model-fitting on data from 180-pairs of twins is 0.61 (0.52-0.70), the rest of the variance in DHEAS levels could be explained by unique environmental influences and age. The heritabilities of DHEAS in two pubertal sub-groups (PH-I and PH-II-V) are 0.82 (0.71-0.90) and 0.63 (0.52-0.74), respectively. The heritability index of menarche, breast development and pube development are 0.71, 0.35 and 0.45, respectively.

CONCLUSIONS

Serum DHEAS concentrations of pubertal girls are mainly influenced by genetic factors, especially during the period of adrenarche. The results stress the importance of research into the genetic regulation of the endocrine regulators involved in adrenarche and related metabolic disorders in girls.

Life history factors, personality and the social clustering of sexual experience in adolescents

Adolescent sexual behaviour may show clustering in neighbourhoods, schools and friendship networks. This study aims to assess how experience with sexual intercourse clusters across the social world of adolescents and whether predictors implicated by life history theory or personality traits can account for its between-individual variation and social patterning. Using data on 2877 adolescents from the Avon Longitudinal Study of Parents and Children, we ran logistic multiple classification models to assess the clustering of sexual experience by approximately 17.5 years in schools, neighbourhoods and friendship networks. We examined how much clustering at particular levels could be accounted for by life history predictors and Big Five personality factors. Sexual experience exhibited substantial clustering in friendship networks, while clustering at the level of schools and neighbourhoods was minimal, suggesting a limited role for socio-ecological influences at those levels. While life history predictors did account for some variation in sexual experience, they did not explain clustering in friendship networks. Personality, especially extraversion, explained about a quarter of friends' similarity. After accounting for life history factors and personality, substantial unexplained similarity among friends remained, which may reflect a tendency to associate with similar individuals or the social transmission of behavioural norms.

Sleep and Lipid Profile During Transition from Childhood to Adolescence

OBJECTIVES

To assess the longitudinal effects of sleep duration and quality on lipid profiles during the transition from childhood to early adolescence, over a 4-year-period.

STUDY DESIGN

A cohort study of children born in 1998 examined at 8 years of age (SD, 0.3; n = 105) and 12 years of age (SD, 0.5; n = 190). Sleep duration, wake after sleep onset, sleep efficiency, and weekend catch-up sleep were measured with actigraphs for 7 (8 years of age) and 8 (12 years of age) nights. Fasting serum samples were collected at 12 years of age. Covariates included age, pubertal development, socioeconomic status, body mass index, and physical activity.

RESULTS

In girls, shorter sleep duration at 8 and 12 years of age was associated with lower high-density lipoprotein-cholesterol and higher triglycerides at 12 years of age. Poorer sleep quality at 8 years of age and longer weekend catch-up sleep at 12 years of age was associated with higher triglycerides at 12 years of age. From 8 to 12 years of age, improvement in sleep quality associated with higher total cholesterol, and a decrease in sleep duration with lower lipid levels. In boys, longer sleep duration at 8 years of age, and a larger decrease in sleep duration from 8 to 12 years of age was associated with higher levels of triglycerides at 12 years of age.

CONCLUSIONS

Poorer sleep during transition to early adolescence is associated with an atherogenic lipid profile in early adolescent girls, and such effects are less prominent in boys. Poor sleep may have long-term associations with health, which are not mitigated by the amount of physical activity.

Pubertal Onset in Boys and Girls Is Influenced by Pubertal Timing of Both Parents

CONTEXT

Epidemiological evidence on maternal and paternal heritability of the wide normal variation within pubertal timing is sparse.

OBJECTIVE

We aimed to estimate the impact of parental pubertal timing on the onset of puberty in boys and girls.

DESIGN

Annual pubertal examinations of healthy children in a longitudinal cohort study. Information on parental timing of puberty (earlier, comparable to, or later compared to peers) and menarche age was retrieved from questionnaires.

PARTICIPANTS

A total of 672 girls and 846 boys.

MAIN OUTCOME MEASURES

Age at onset of pubic hair (PH2+), breasts (B2+), and menarche in girls; and PH2+, genital stage (G2+), and testis >3 mL with orchidometer (Tvol3+) in boys.

RESULTS

In boys, pubertal onset was significantly associated with pubertal timing of both parents. PH2+ and Tvol3+ were earlier: -11.8 months (95% confidence interval, -16.8, -6.8)/-8.9 (-12.8, -4.9), and -9.5 (-13.9, -5.1)/-7.1 (-10.4, -3.7) if the father/mother, respectively, had early pubertal development compared to late. In girls, menarche was significantly associated with both parents' pubertal timing: -10.5 months (-15.9, -5.1)/-10.1 (-14.3, -6.0) if father/mother had early pubertal development compared to late. For the onset of PH2+ and B2+ in girls, estimates were -7.0 months (-12.6, -1.4) and -4.1 (-10.6, +2.4)/-6.7 (-11.0, -2.5), and -6.7 (-11.0, -2.0) for fathers/mothers, respectively. Maternal age of menarche was significantly associated with the onset of all pubertal milestones except PH2+ in girls.

CONCLUSIONS

Maternal as well as paternal pubertal timing was a strong determinant of age at pubertal onset in both girls and boys. Age at breast and pubic hair development in girls, which has declined most during recent years, seemed to be least dependent on heritability.

Prepubertal Serum Concentrations of Organochlorine Pesticides and Age at Sexual Maturity in Russian Boys

BACKGROUND

Few human studies have evaluated the impact of childhood exposure to organochlorine pesticides (OCP) on pubertal development.

OBJECTIVE

We evaluated associations of serum OCP concentrations [hexachlorobenzene (HCB), β-hexachlorocyclohexane (βHCH), and p,p-dichlorodiphenyldichloroethylene (p,p´-DDE)] with age at attainment of sexual maturity among boys.

METHODS

From 2003 through 2005, 350 8- to 9-year-old boys from Chapaevsk, Russia, with measured OCPs were enrolled and followed annually for 8 years. We used multivariable interval-censored models to evaluate associations of OCPs (quartiles) with three physician-assessed measures of sexual maturity: Tanner stage 5 for genitalia growth, Tanner stage 5 for pubic hair growth, or testicular volume (TV) ≥ 20 mL in either testis.

RESULTS

In adjusted models, boys with higher HCB concentrations achieved sexual maturity reflected by TV ≥ 20 mL a mean of 3.1 months (95% CI: -1.7, 7.8), 5.3 months (95% CI: 0.6, 10.1), and 5.0 months (95% CI: 0.2, 9.8) later for quartiles Q2, Q3, and Q4, respectively, compared with Q1 (p trend = 0.04). Tanner stage 5 for genitalia growth was attained a mean of 2.2 months (95% CI: -3.1, 7.5), 5.7 months (95% CI: 0.4, 11.0), and 3.7 months (95% CI: -1.7, 9.1) later for quartiles Q2, Q3, and Q4, respectively, of βHCH compared with Q1 (p trend = 0.09). Tanner stage 5 for pubic hair growth occurred 6-9 months later on average for boys in the highest versus lowest quartile for HCB (p trend < 0.001), βHCH (trend p = 0.01), and p,p´-DDE (p trend = 0.04). No associations were observed between p,p´-DDE and Tanner stage 5 for genitalia growth or TV ≥ 20 mL.

CONCLUSIONS AND RELEVANCE

Higher prepubertal serum HCB and βHCH concentrations were associated with a later age at attainment of sexual maturity. Only the highest quartile of serum p,p´-DDE was associated with later pubic hair maturation.

CITATION

Lam T, Williams PL, Lee MM, Korrick SA, Birnbaum LS, Burns JS, Sergeyev O, Revich B, Altshul LM, Patterson DG Jr, Hauser R. 2015. Prepubertal serum concentrations of organochlorine pesticides and age at sexual maturity in Russian boys. Environ Health Perspect 123:1216-1221; http://dx.doi.org/10.1289/ehp.1409022.

Prevalence and factors associated with stunting and thinness among adolescent students in Northern Ethiopia: a comparison to World Health Organization standards

BACKGROUND

Adolescence is last chance for curbing the consequences of malnutrition and breaking the intergenerational cycle of malnutrition and poor health. This study aimed to assess the prevalence and the factors associated with stunting and thinness among in-school adolescents in northern Ethiopia using the 2006 World Health Organization (WHO) standards.

METHODS

In-school adolescents (n = 348, 10-19 years old) were randomly selected to participate in this cross-sectional study. Anthropometric measurements were carried out to determine the proportion of adolescents who were stunted (height-for-age < -2 Standard Deviation (SD)) and thin (body-mass-index-for-age < -2 SD). T-test was employed to evaluate mean weight and height differences between groups. Pearson chi-square, chi-square trend and Fisher's exact tests were used to explore the crude association of categorical outcome variables and associated factors. Crude and adjusted associations between the outcome variables (stunting and thinness) and independent variables (socio-demographic, eating behavior and sanitation) were also determined using logistic regression. Stata version 11.1 was used to analyze the data.

RESULTS

The height of the adolescents was 147.6 ± 11.2 cm (mean ± SD) and weight was37.2 ± 9.5 kg. The mean Z-scores of height-for-age and body-mass-index (BMI)-for-age of adolescents were -1.49 and -1.29, respectively. The prevalence of stunting and thinness among adolescents was 28.5 % (boys = 37.7 %; girls = 21.2 %; P = 0.001) and 26.1 % (boys = 32.4; girls = 21.6 %; p = 0.017), respectively. Adolescents in 13-15 year old age group (Adjusted Odds ratio (AOR) = 2.23; 95 % CI: 1.22, 4.08), boys (AOR = 2.53; 95 % CI: 1.52, 4.21) and rural residents (AOR = 2.15; 95 % CI: 1.20, 3.86) had significantly higher odds of being stunted compared to their counterparts. Furthermore, boys had higher (AOR = 1.97; 95 % CI: 1.19, 3.25) odds of being thin compared to girls. Compared to those 10 to 12 years of age, adolescents in 16 to 19 years of age were 53 % (AOR = 0.47; 95 % CI: 0.23, 0.95) less likely to be thin.

CONCLUSIONS

Undernutrition is widely prevalent among adolescents in northern Ethiopia. Sex, age and area of residence significantly associated with adolescent undernutrition. The study underlines the need for nutrition interventions targeting rural and boy adolescents.

Poor sleep and neurocognitive function in early adolescence

BACKGROUND

Evidence regarding the associations between sleep duration and quality, and neurocognitive function in adolescents remains scanty. This study examined the associations in early adolescence between: sleep duration; efficiency; fragmentation; wake-after-sleep-onset (WASO); catch-up sleep; intelligence; memory; and executive function, including attention.

METHODS

This study included 354 girls and boys with a mean age 12.3 years (SD = 0.5) from a birth cohort born in 1998. Sleep was measured with accelerometers for an average of eight nights. Cognitive function was evaluated with subtests from the Wechsler Intelligence Scale for Children-III (WISC-III), the Developmental Neuropsychological Assessment 2 (NEPSY-2), the Wisconsin Card Sorting Task (WCST), Conners' Continuous Performance Task (CPT), and the Trail Making Test (TMT).

RESULTS

In girls, a higher WASO and fragmentation index were associated with poorer executive functioning (higher number of perseverative errors in the WCST), and longer catch-up sleep was associated with longer reaction times and better performance in one verbal intelligence test (Similarities subtest of the WISC-III). In boys, shorter sleep duration, lower efficiency, higher WASO, higher sleep fragmentation and shorter catch-up sleep were associated with lower executive functioning (more commission errors, shorter reaction times, and had lower D Prime scores in CPT).

CONCLUSIONS

In adolescent girls, poorer sleep quality was only weakly associated with poorer executive functioning, while in boys, poorer sleep quantity and quality were associated with an inattentive pattern of executive functioning. The amount of catch-up sleep during weekends showed mixed patterns in relation to neurocognitive function.

Genetic influences on pubertal development and links to behavior problems

Genetic influences on adolescent psychological development are likely to be mediated and moderated by pubertal hormones. Combining genetic analyses with advanced models of pubertal development, we extended work on the measurement and psychological significance of puberty. We examined how genetic and environmental influences on puberty vary by the way that development is described (logistic versus linear models versus traditional methods) and the different aspects of puberty (adrenarche vs. gonadarche), and how genes and environment contribute to the covariation between different descriptions and aspects of puberty, and between pubertal development and behavior problems (substance use, age at sexual initiation). We also considered how puberty moderated the heritability of psychological outcomes (internalizing and externalizing problems), and sex differences. Participants from the Colorado Longitudinal Twin Study (403 girls, 395 boys) reported their pubertal development annually from ages 9 through 15; they and their parents reported their behavior in mid-to-late adolescence. There was a large genetic contribution to pubertal timing for both sexes no matter how it was measured, but findings for pubertal tempo varied by method. Genetic covariation accounted for most of the phenotypic correlations among different indicators of pubertal timing, and between pubertal timing and psychological outcome. We consider the implications of our results for understanding how pubertal hormones mediate or moderate genetic and environmental influences on psychological development.

Genetic and Environmental Contributions to Covariation Between DHEA and Testosterone in Adolescent Twins

Although several studies have shown that pubertal tempo and timing are shaped by genetic and environmental factors, few studies consider to what extent endocrine triggers of puberty are shaped by genetic and environmental factors. Doing so moves the field from examining correlated developmentally-sensitive biomarkers toward understanding what drives those associations. Two puberty related hormones, dehydroepiandrosterone and testosterone, were assayed from salivary samples in 118 MZ (62 % female), 111 same sex DZ (46 % female) and 103 opposite-sex DZ twin pairs, aged 12-16 years (M = 13.1, SD = 1.3). Pubertal status was assessed with a composite of mother- and self-reports. We used biometric models to estimate the genetic and environmental influences on the variance and covariance in testosterone and DHEA, with and without controlling for their association with puberty, and to test for sex differences. In males, the variance in testosterone and pubertal status was due to shared and non-shared environmental factors; variation in DHEA was due to genetic and non-shared environmental factors. In females, variance in testosterone was due to genetic and non-shared environmental factors; genetic, shared, and non-shared environmental factors contributed equally to variation in DHEA. In males, the testosterone-DHEA covariance was primarily due to shared environmental factors that overlapped with puberty as well as shared and non-shared environmental covariation specific to testosterone and DHEA. In females, the testosterone-DHEA covariance was due to genetic factors overlapping with pubertal status, and shared and non-shared environmental covariation specific to testosterone and DHEA.

Prepubertal organochlorine pesticide concentrations and age of pubertal onset among Russian boys

BACKGROUND

In animal studies, organochlorine pesticide (OCP) exposure alters pubertal development; however, epidemiological data are limited and inconsistent.

OBJECTIVE

To evaluate the associations of serum OCP concentrations [hexachlorobenzene (HCB), β-hexachlorocyclohexane (β-HCH), and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE)] with male pubertal onset.

METHODS

In Chapaevsk, Russia, a town environmentally contaminated with OCPs, 350 8-9 year old boys with measured OCPs were enrolled during 2003-2005 and were followed annually for eight years. We evaluated three measures of pubertal onset: testicular volume (TV)>3 mL in either testis, or stage 2 or greater for genitalia (G2+), or pubic hair (P2+). We used multivariable interval-censored models to evaluate associations of OCPs (quartiles) with physician-assessed pubertal onset.

RESULTS

In adjusted models, boys with higher HCB concentrations had later mean ages of TV>3 mL and P2+ (but not G2+). Mean age at attaining TV>3 mL was delayed 3.6 (95% CI: -2.6, 9.7), 7.9 (95% CI: 1.7, 14.0), and 4.7 months (95% CI: -1.4, 10.9) for HCB Q2, Q3, and Q4, respectively, compared to Q1 (trend p: 0.06). Boys with higher HCB concentrations reached P2+ 0.1 months earlier (95% CI: -5.8, 5.6) for Q2, 4.7 months later (95% CI: -1.0, 10.3) for Q3 and 4.6 months later (95% CI: -1.1, 10.3) for Q4 compared to Q1 (trend p: 0.04). There were no associations of serum β-HCH and p,p'-DDE concentrations with age of pubertal onset.

CONCLUSION

Higher prepubertal serum HCB concentrations were associated with later age of gonadarche and pubarche.

The associations between adolescent sleep, diurnal cortisol patterns and cortisol reactivity to dexamethasone suppression test

Information on the associations between objectively measured sleep and hypothalamic-pituitary-adrenal axis function in early adolescence is scarce. We examined associations between average sleep duration and quality (sleep efficiency and wake after sleep onset) over 8 days with actigraphs and (1) diurnal cortisol patterns and (2) cortisol reactivity to a low-dose (3 μg/kg) overnight dexamethasone suppression test (DST) in a birth cohort born in 1998 (N=265 participants, mean age 12.3 years, SD=0.5). We also explored (3) if sleep duration and quality were affected the nights after the DST exposure. Cortisol was measured during 2 days, and participants were exposed to dexamethasone in the evening of first day. In boys, short sleep duration was associated with higher cortisol upon awakening and lower cortisol awakening response (CAR; P<0.05 and P<0.01). Long sleep duration in boys associated with higher CAR (P<0.02). Lower sleep quality in boys associated with lower CAR, but fell slightly short of significance (P<0.06). In girls, no significant associations were detected. Sleep quantity and quality were not associated with responses to the DST. There were no effects of DST on sleep (P>0.15 in between-subject analyses). The average sleep patterns showed associations with diurnal cortisol patterns during early adolescence, but only in boys. Sleep was not associated with cortisol reactivity to DST and the exogenous corticosteroid exposure did not affect sleep significantly.

Behavior problems and timing of menarche: a developmental longitudinal biometrical analysis using the NLSY-Children data

A powerful longitudinal data source, the National Longitudinal Survey of Youth Children data, allows measurement of behavior problems (BP) within a developmental perspective linking them to menarcheal timing (MT). In a preliminary analysis, we evaluate the bivariate relationships between BP measured at different developmental periods and the timing of menarche. Correlations were not consistent with any correlational/causal relationship between BP and MT. In the major part of our study, MT was used to moderate the developmental trajectory of BP, within a genetically-informed design. Girls reaching menarche early had behavior problem variance accounted for by the shared environment; those reaching menarche with average/late timing had behavior problem differences accounted for by genetic variance. Our findings match previous empirical results in important ways, and also extend those results. A theoretical interpretation is offered in relation to a theory linking genetic/shared environmental variance to flexibility and choices available within the family in relation to BP.

Child maltreatment and household dysfunction: associations with pubertal development in a British birth cohort

BACKGROUND

We aimed to establish the association between adverse childhood experiences (maltreatment and household dysfunction) and pubertal maturation, which is associated with later health outcome(s).

METHODS

The 1958 British birth cohort (n = 17 638) includes all born in one week, March 1958, followed up to mid adulthood. Pubertal stage was rated by medical personnel at 11 and 16 years of age (y). Childhood maltreatment (neglect or abuse) and household dysfunction scores were constructed from information ascertained in childhood and at 45 y.

RESULTS

Childhood neglect, assessed at 7 y, was associated with late pubertal development on several markers after adjusting for early life circumstances: relative risk ratio (RRRadjusted) was 1.13 (95% CI: 1.06,1.21) and 1.06 (1.00,1.12) for late menarche and breast development (females) per unit increase in neglect score ranging 0-7, respectively; 1.14 (1.08,1.20) for late voice change and 1.07 (1.02,1.13) for pubic hair growth (males). The RRRadjusted for late pubic hair (females) and genitalia and facial hair (males) development was 1.04 (P = 0.052 to 0.085). Abuse score (0-3, for physical, sexual or psychological abuse) was associated in females with late menarche [RRRadjusted = 1.17 (1.01,1.36)] and in males with late pubic hair growth [RRRadjusted = 1.16 (1.01,1.34)] per unit increase, but not with other pubertal markers. Neither score (neglect or abuse) was associated with early puberty, but sexual abuse was associated with early [RRRadjusted = 1.86 (1.06,3.29)] as well as late menarche [RRRadjusted = 1.66 (1.02,2.71)] and witnessing abuse with early genitalia development [RRRadjusted = 1.57 (1.02,2.41)]. Household dysfunction score was not associated consistently with pubertal markers.

CONCLUSIONS

Cumulative neglect by 7 y was associated with delayed development of several pubertal markers. The underlying role of pubertal development in linking childhood neglect with future adult health warrants further consideration.

A Life History Theory of Father Absence and Menarche: A Meta-Analysis

Is the absence of biological fathers related to their daughters' earlier age at menarche? Drawing on evolutionary psychology and life history theory, prior research has suggested such a relationship ( Belsky, Steinberg, and Draper, 1991 ; Draper and Harpending, 1982 ; Ellis, 2004 ). Although qualitative reviews have shown narrative support for this relationship ( Allison and Hyde, 2013 ; Ellis, 2004 ; Kim, Smith, and Palermiti, 1997 ; Susman and Dorn, 2009 ), no quantitative review exists to provide empirical support for this relationship or to explain mixed results. Thus, we conducted a random-effects meta-analysis of correlations ( Card, 2012 ) on father absence and daughter menarcheal age ( k = 33; N = 70,403). The weighted mean correlation was .14, 95% CI [.09, .19], suggesting that father absence was significantly related to earlier menarche; effect sizes were heterogeneous. Egger's regression ( Egger, Smith, Schneider, and Minder, 1997 ) showed no evidence of publication bias (file-drawer effect; r = .34, p = .052). Outcome measure differences (menarcheal age vs. menarcheal age embedded in a multi-item pubertal timing scale) did not moderate effect sizes. Study year effects ( Schooler, 2011 ) were also non-significant. Our findings support one aspect of the life history model and provide groundwork for subsequent examination of other pathways in the model.

Continuity and change in poor sleep from childhood to early adolescence

STUDY OBJECTIVES

We examined associations between pubertal maturation and sleep in early adolescence, at age 12 y, and continuity and change in actigraphy-based sleep and parent-reported sleep disorders from age 8 to 12 y. We also explored longitudinal associations between actigraph estimates of sleep and sleep disorders.

DESIGN

A cohort study of children born in 1998 and tested at ages 8 y (standard deviation [SD] = 0.3) and 12 y (SD = 0.5).

PARTICIPANTS

A total of 348 children participated in cross-sectional analyses. We had longitudinal actigraphy data for 188 children and repeated parent reports of sleep disorders for 229 children.

MEASUREMENTS AND RESULTS

At age 8 y, participants wore actigraphs for 7.1 nights (SD = 1.2, range 3-14) on average and at age 12 y for 8.4 nights (SD = 1.7, range 3-11). Sleep disorders were parent-rated based on the Sleep Disturbance Scale for Children. Pubertal maturity was self-reported at age 12 y using the continuous Pubertal Development Scale and the picture-assisted categorical Tanner scales.

RESULTS

Significant mean-level changes toward shorter but higher quality sleep occurred over time. Sleep variables had low to high rank-order stability over time. Sleep disorders were highly stable from age 8 to 12 y. Actigraphy-based sleep and parent-rated sleep disorders showed no association either in cross-section or longitudinally. Pubertal maturation was not associated with worse sleep.

CONCLUSIONS

Sleep in early adolescence can be anticipated from childhood sleep patterns and disorders, but is not associated with pubertal maturity. Although sleep duration becomes shorter, sleep quality may improve during early adolescence. Parent-rated sleep disorders are distinct from actigraph estimates of sleep.

Genetic influences on adolescent sexual behavior: Why genes matter for environmentally oriented researchers

There are dramatic individual differences among adolescents in how and when they become sexually active adults, and early sexual activity is frequently cited as a cause of concern for scientists, policymakers, and the general public. Understanding the causes and developmental impact of adolescent sexual activity can be furthered by considering genes as a source of individual differences. Quantitative behavioral genetics (i.e., twin and family studies) and candidate gene association studies now provide clear evidence for the genetic underpinnings of individual differences in adolescent sexual behavior and related phenotypes. Genetic influences on sexual behavior may operate through a variety of direct and indirect mechanisms, including pubertal development, testosterone levels, and dopaminergic systems. Genetic differences may be systematically associated with exposure to environments that are commonly treated as causes of sexual behavior (gene-environment correlation). Possible gene-environment correlations pose a serious challenge for interpreting the results of much behavioral research. Multivariate, genetically informed research on adolescent sexual behavior compares twins and family members as a form of quasi experiment: How do twins who differ in their sexual experiences differ in their later development? The small but growing body of genetically informed research has already challenged dominant assumptions regarding the etiology and sequelae of adolescent sexual behavior, with some studies indicating possible positive effects of teenage sexuality. Studies of Gene × Environment interaction may further elucidate the mechanisms by which genes and environments combine to shape the development of sexual behavior and its psychosocial consequences. Overall, the existence of heritable variation in adolescent sexual behavior has profound implications for environmentally oriented theory and research.

Prevalence, comorbidity and heritability of hoarding symptoms in adolescence: a population based twin study in 15-year olds

BACKGROUND

Hoarding Disorder (HD) is often assumed to be an 'old age' problem, but many individuals diagnosed with HD retrospectively report first experiencing symptoms in childhood or adolescence. We examined the prevalence, comorbidity and etiology of hoarding symptoms in adolescence.

METHODS

To determine the presence of clinically significant hoarding symptoms, a population-based sample of 15-year old twins (N = 3,974) completed the Hoarding Rating Scale-Self Report. Co-occurring Obsessive Compulsive Disorder (OCD), Autism Spectrum Disorders (ASD) and Attention Deficit Hyperactivity Disorder (ADHD) were estimated from parental report. Model-fitting analyses divided hoarding symptom scores into additive genetic, shared, and non-shared environmental effects.

RESULTS

The prevalence of clinically significant hoarding symptoms was 2% (95% CI 1.6-2.5%), with a significantly higher prevalence in girls than boys. Exclusion of the clutter criterion (as adolescents do not have control over their environment) increased the prevalence rate to 3.7% (95% CI 3.1-4.3%). Excessive acquisition was reported by 30-40% among those with clinically significant hoarding symptoms. The prevalence of co-occurring OCD (2.9%), ASD (2.9%) and ADHD (10.0%) was comparable in hoarding and non-hoarding teenagers. Model-fitting analyses suggested that, in boys, additive genetic (32%; 95% CI 13-44%) and non-shared environmental effects accounted for most of the variance. In contrast, among girls, shared and non-shared environmental effects explained most of the variance, while additive genetic factors played a negligible role.

CONCLUSIONS

Hoarding symptoms are relatively prevalent in adolescents, particularly in girls, and cause distress and/or impairment. Hoarding was rarely associated with other common neurodevelopmental disorders, supporting its DSM-5 status as an independent diagnosis. The relative importance of genetic and shared environmental factors for hoarding differed across sexes. The findings are suggestive of dynamic developmental genetic and environmental effects operating from adolescence onto adulthood.

Early puberty and childhood social and behavioral adjustment

PURPOSE

Early puberty has been linked to higher rates of mental health problems in adolescence. However, previous studies commencing after the initiation of puberty have been unable to explore whether early puberty is preceded by higher rates of these problems. In a large national study, we aimed to determine whether difficulties in behavior and psychosocial adjustment are evident before as well as during the early pubertal transition.

METHODS

The Longitudinal Study of Australian Children recruited a nationally representative cohort of 4,983 children at age 4-5 years in 2004. This analysis includes 3,491 of these children (70.1%) followed up at ages 6-7, 8-9, and 10-11 years, with a completed parent report of stage of pubertal maturation at age 8-9 years. Parents reported behavior difficulties (Strengths and Difficulties Questionnaire) and psychosocial adjustment (Pediatric Quality of Life Inventory) at all four waves from ages 4-5 to 10-11 years.

RESULTS

Both boys and girls who entered puberty early (i.e., by age 8-9 years) also experienced poorer psychosocial adjustment at this age. These psychosocial differences were already evident at ages 4-5 and 6-7 years, and persisted to at least age 10-11 years. Similar patterns were evident for behavior difficulties, but only for boys; early puberty was not related to behavior difficulties in girls.

CONCLUSIONS

Children with early puberty have different patterns of behavior and social adjustment from the preschool years through early adolescence. At least in part, the association between early-onset puberty and poor mental health appears to result from processes under way well before the onset of puberty.

Food insecurity and linear growth of adolescents in Jimma Zone, Southwest Ethiopia

Background

Although many studies showed that adolescent food insecurity is a pervasive phenomenon in Southwest Ethiopia, its effect on the linear growth of adolescents has not been documented so far. This study therefore aimed to longitudinally examine the association between food insecurity and linear growth among adolescents.

Methods

Data for this study were obtained from a longitudinal survey of adolescents conducted in Jimma Zone, which followed an initial sample of 2084 randomly selected adolescents aged 13–17 years. We used linear mixed effects model for 1431 adolescents who were interviewed in three survey rounds one year apart to compare the effect of food insecurity on linear growth of adolescents.

Results

Overall, 15.9% of the girls and 12.2% of the boys (P=0.018) were food insecure both at baseline and on the year 1 survey, while 5.5% of the girls and 4.4% of the boys (P=0.331) were food insecure in all the three rounds of the survey. In general, a significantly higher proportion of girls (40%) experienced food insecurity at least in one of the survey rounds compared with boys (36.6%) (P=0.045).

The trend of food insecurity showed a very sharp increase over the follow period from the baseline 20.5% to 48.4% on the year 1 survey, which again came down to 27.1% during the year 2 survey.

In the linear mixed effects model, after adjusting for other covariates, the mean height of food insecure girls was shorter by 0.87 cm (P<0.001) compared with food secure girls at baseline. However, during the follow up period on average, the heights of food insecure girls increased by 0.38 cm more per year compared with food secure girls (P<0.066). However, the mean height of food insecure boys was not significantly different from food secure boys both at baseline and over the follow up period. Over the follow-up period, adolescents who live in rural and semi-urban areas grew significantly more per year than those who live in the urban areas both for girls (P<0.01) and for boys (P<0.01).

Conclusions

Food insecurity is negatively associated with the linear growth of adolescents, especially on girls. High rate of childhood stunting in Ethiopia compounded with lower height of food insecure adolescents compared with their food secure peers calls for the development of direct nutrition interventions targeting adolescents to promote catch-up growth and break the intergenerational cycle of malnutrition.

Childhood adversity and pubertal timing: understanding the origins of adulthood cardiovascular risk

OBJECTIVE

To determine whether greater childhood adversity relates to younger menarcheal age; whether younger menarcheal age relates to increased CVD risk; and whether greater childhood adversity relates to increased CVD risk, directly or indirectly (mediated by menarcheal age).

METHODS

Among 650 pre-menopausal women (ages 25-45; M=34.9[5.6]), SEM was performed to estimate relations between childhood adversity, menarcheal age, and CVD risk.

RESULTS

Results supported a covariate-adjusted model (RMSEA=0.035; CFI=0.983) in which greater childhood adversity was related to younger menarcheal age (β=-.13, p<.01) and younger menarcheal age was related to greater CVD risk (β=-.18, p<.05). Direct and indirect effects of childhood adversity on CVD risk were non-significant. Re-evaluation of the same model with additional covariate-adjustment for adulthood body composition showed the relation between menarcheal age and CVD risk attenuated (β=-.03, p=.376).

CONCLUSIONS

Cross-sectional evidence suggests family-related adversity experiences in childhood confer risk for earlier menarche which, in turn, relates to increased CVD risk in adulthood, possibly via post-pubertal body size.

Genetic and environmental influences on the association between pubertal maturation and internalizing symptoms

The literature consistently shows an association between pubertal maturation and internalizing problems in girls. The association for boys is less clear. The present study examines genetic and environmental influences on the association between pubertal maturation and internalizing problems for boys and girls in two primarily Caucasian adolescent twin/sibling studies: The Swedish Twin study of CHild and Adolescent Development (706 same-sex twin pairs aged 13-14, M = 13.7 years, 50 % female), and the Nonshared Environment in Adolescent Development sample (US-based, 687 same-sex twin/sibling pairs aged 10-18, M = 13.6 years, 47 % female). For girls, more advanced pubertal maturation was associated modestly with more internalizing problems, and that association was entirely explained by shared environmental influences. For boys, the association between pubertal maturation and internalizing problems was weak and inconsistent. Results for girls were remarkably consistent across samples. Findings suggest that nongenetic mechanisms mediate the association between pubertal maturation and internalizing problems. Findings have implications for intervention such that environmental influences shared by twins/siblings may provide the best targets for intervention strategies designed to minimize the potential negative effects of pubertal maturation on internalizing symptoms in girls.

Heritability of Testosterone Levels in 12-Year-Old Twins and Its Relation to Pubertal Development

The aim of this study was to estimate the heritability of variation in testosterone levels in 12-year-old children, and to explore the overlap in genetic and environmental influences on circulating testosterone levels and androgen-dependent pubertal development. Midday salivary testosterone samples were collected on 2 consecutive days in a sample of 183 unselected twin pairs. Androgen-induced pubertal development was assessed using self-report Tanner scales of pubic hair development (boys and girls) and genital development (boys). A significant contribution of genetic effects to the variance in testosterone levels was found. Heritability was approximately 50% in both boys and girls. The remaining proportion of the variance in testosterone levels could be explained by nonshared environmental influences. The relatively high correlation between testosterone levels of opposite-sex dizygotic twins suggests that sex differences in genes influencing variation in testosterone levels have not yet developed in preand early puberty. Variance in pubertal development was explained by a large genetic component, moderate shared environmental influences, and a small nonshared environmental effect. Testosterone levels correlated moderately (r = .31) with pubertal development; the covariance between testosterone levels and pubertal development was entirely accounted for by genetic influences.

Parameterization of Sex-Limited Autosomal Linkage Analysis for Mx

Incorporation of sex-limitation (genotype-sex interaction) effects into a model of quantitative trait loci (QTL) analysis has been shown to increase the power to detect linkage when analyzing traits in which sex limitation is present (Towne et al., 1997). The present note provides a parameterization of the nonscalar sex-limitation ACE model incorporating autosomal sex-limited QTL effects for use with the Mx matrix algebra program (Neale et al., 2002). An example script designed for use with extended sib- ships that takes advantage of the versatile treatment of covariates within Mx is included.

Gene-environment interplay in the association between pubertal timing and delinquency in adolescent girls

Early pubertal timing places girls at elevated risk for a breadth of negative outcomes, including involvement in delinquent behavior. While previous developmental research has emphasized the unique social challenges faced by early maturing girls, this relation is complicated by genetic influences for both delinquent behavior and pubertal timing, which are seldom controlled for in existing research. The current study uses genetically informed data on 924 female-female twin and sibling pairs drawn from the National Longitudinal Study of Adolescent Health to (1) disentangle biological versus environmental mechanisms for the effects of early pubertal timing and (2) test for gene-environment interactions. Results indicate that early pubertal timing influences girls' delinquency through a complex interplay between biological risk and environmental experiences. Genes related to earlier age at menarche and higher perceived development significantly predict increased involvement in both nonviolent and violent delinquency. Moreover, after accounting for this genetic association between pubertal timing and delinquency, the impact of nonshared environmental influences on delinquency are significantly moderated by pubertal timing, such that the nonshared environment is most important among early maturing girls. This interaction effect is particularly evident for nonviolent delinquency. Overall, results suggest early maturing girls are vulnerable to an interaction between genetic and environmental risks for delinquent behavior.

Environmental and genetic pathways between early pubertal timing and dieting in adolescence: distinguishing between objective and subjective timing

BACKGROUND

Early pubertal timing in girls is associated with elevated risk for dieting and eating pathology. The relative importance of biological versus socio-environmental mechanisms in explaining this association remains unclear. Moreover, these mechanisms may differ between objective measures of pubertal development and girls' subjective perceptions of their own maturation.

METHOD

The sample comprised 924 sister pairs from the National Longitudinal Study of Adolescent Health. Objective pubertal timing (menarcheal age), girls' perceptions of pubertal status and timing relative to peers, dieting and disordered eating behaviors were assessed during a series of confidential in-home interviews.

RESULTS

Behavioral genetic models indicated that common genetic influences accounted for the association between early menarcheal age and increased risk for dieting in adolescence. In contrast, girls' subjective perceptions of their timing relative to peers were associated with dieting through an environmental pathway. Overall, subjective and objective measures of pubertal timing accounted for 12% of the variance in dieting.

CONCLUSIONS

Genetic differences in menarcheal age increase risk for dieting among adolescent girls, while girls' perceptions of their maturation represent an environmentally mediated risk.

Associations Between Early Life Stress, Child Maltreatment, and Pubertal Development Among Girls in Foster Care

The present study investigated pubertal development in girls with maltreatment histories (N = 100), assessed at four time points over 2 years beginning in the spring of their final year of elementary school. This sample is unique, in that participants were subject to an unusual level of environmental risk early in life and resided in foster care at the start of the study. Analyses replicated the previously established association between sexual abuse and earlier onset of maturation and earlier age at menarche. Physical abuse was related to a more rapid tempo of pubertal development across the period assessed. These results strengthen previous investigations of childhood maltreatment and puberty, highlighting the complexity and specificity of early life experiences for later development.

Pubertal timing and early sexual intercourse in the offspring of teenage mothers

Early puberty is associated with stressful family environments, early sexual intercourse, and teenage pregnancy. We examined pubertal timing and sexual debut among the 14-year-old offspring of teenage mothers. Mothers (71% Black, 29% White) were recruited as pregnant teenagers (12-18 years old). Data were collected during pregnancy and when offspring were 6, 10 and 14 years old (n = 318). Adolescents (50% male) compared the timing of their pubertal maturation to same-sex peers. There was a significant 3-way interaction effect of race, sex, and pubertal timing on sexual debut (n = 305). This effect remained significant in a model controlling for maternal age at first intercourse, substance use, exposure to trauma, authoritative parenting, and peer sexual activity (n = 255). Early maturation was associated with early sex in daughters, and may be one pathway for the inter-generational transfer of risk for teenage pregnancy among daughters of teenage mothers.

Quality of early family relationships and the timing and tempo of puberty: effects depend on biological sensitivity to context

Guided by evolutionary-developmental theories of biological sensitivity to context and reproductive development, the current research examined the interactive effects of early family environments and psychobiologic reactivity to stress on the subsequent timing and tempo of puberty. As predicted by the theory, among children displaying heightened biological sensitivity to context (i.e., higher stress reactivity), higher quality parent-child relationships forecast slower initial pubertal tempo and later pubertal timing, whereas lower quality parent-child relationships forecast the opposite pattern. No such effects emerged among less context-sensitive children. Whereas sympathetic nervous system reactivity moderated the effects of parent-child relationships on both breast/genital and pubic hair development, adrenocortical activation only moderated the effect on pubic hair development. The current results build on previous research documenting what family contexts predict variation in pubertal timing by demonstrating for whom those contexts matter. In addition, the authors advance a new methodological approach for assessing pubertal tempo using piecewise growth curve analysis.

Pubertal development moderates the importance of environmental influences on depressive symptoms in adolescent girls and boys

Prevalence differences in depressive symptoms between the sexes typically emerge in adolescence, with symptoms more prevalent among girls. Some evidence suggests that variation in onset and progression of puberty might contribute to these differences. This study used a genetically informative, longitudinal (assessed at ages 12, 14, and 17) sample of Finnish adolescent twins (N = 1214, 51.6% female) to test whether etiological influences on depressive symptoms differ as a function of pubertal status. These tests were conducted separately by sex, and explored longitudinal relationships. Results indicated that pubertal development moderates environmental influences on depressive symptoms. These factors are more important on age 14 depressive symptoms among more developed girls relative to their less developed peers, but decrease in influence on age 17 depressive symptoms. The same effects are observed in boys, but are delayed, paralleling the delay in pubertal development in boys compared to girls. Thus, the importance of environmental influences on depressive symptoms during adolescence changes as a function of pubertal development, and the timing of this effect differs across the sexes.

Adolescent sexual activity and the development of delinquent behavior: the role of relationship context

Despite the well-established association between adolescent sexual activity and delinquent behavior, little research has examined the potential importance of relationship contexts in moderating this association. The current study used longitudinal, behavioral genetic data on 519 same-sex twin pairs (48.6% female) divided into two age cohorts (13-15 and 16-18 years olds) drawn from the National Longitudinal Study of Adolescent Health. Analyses tested whether adolescent sexual activity that occurred in romantic versus non-romantic relationships was associated with delinquency from adolescence to early adulthood, after controlling for genetic influences. Results indicated that, for both younger and older adolescents, common underlying genes influence both sexual behavior and delinquency. After controlling for these genetic influences, there was no within-twin pair association between sexual activity and delinquency in younger adolescents. In older adolescents, sexual activity that occurred in romantic relationships predicted lower levels of delinquency, both cross-sectionally and longitudinally, whereas sexual activity in non-romantic relationships predicted higher levels of delinquency. These results are consistent with emerging research that suggests that the psychological correlates of adolescent sexual activity may be moderated by the social context in which this activity occurs.

Blood lead levels and delayed onset of puberty in a longitudinal study of Russian boys

OBJECTIVE

We evaluated the association of blood lead levels (BLLs) with pubertal onset in a longitudinal cohort of Russian boys.

METHODS

A total of 489 Russian boys were enrolled in 2003-2005, at 8 to 9 years of age, and were monitored annually through May 2008. Cox proportional-hazards models were used to evaluate the association of BLLs at enrollment with time to pubertal onset during follow-up monitoring.

RESULTS

A total of 481 boys had BLLs, with a median of 3 microg/dL and 28% with values of > or =5 microg/dL. The proportion of pubertal boys increased with age, from 12% at age 8 to 83% at age 12 for testicular volume of >3 mL, from 22% to 90% for genitalia stage 2 or higher, and from 4% to 40% for pubic hair stage 2 or higher. After adjustment for potential confounders including BMI and height, boys with high BLLs (> or =5 microg/dL) had 24% to 31% reduced risk of pubertal onset, on the basis of testicular volume of >3 mL (hazard ratio [HR]: 0.73 [95% confidence interval [CI]: 0.55-0.97]; P = .03), genitalia staging (HR: 0.76 [95% CI: 0.59-0.98]; P = .04), and pubic hair staging (HR: 0.69 [95% CI: 0.44-1.07]; P = .10), compared with those with lower BLLs. Pubertal onset occurred 6 to 8 months later, on average, for boys with high BLLs, compared with those with BLLs of <5 microg/dL.

CONCLUSION

Higher BLLs were associated with later pubertal onset in this prospective study of peripubertal Russian boys.

Timing of sexual maturation and women's evaluation of men

Many antecedents and consequences of an accelerated sexual maturation are associated with negative experiences with the opposite sex. Here we show a connection between menarcheal age, a salient sign of female sexual maturation, and the implicit attitude toward men in later adulthood. In Study 1, earlier age at first menstruation was associated with automatic negative evaluations of male faces but not female ones. Study 2 revealed a relationship between early age of menarche and an implicit association between the concepts male and danger. In Study 3, the earlier the menarche, the larger was the estimated egocentric distance of virtual male voices and the shorter the estimated distance of female voices. These results, obtained about a decade after onset of menstruation, suggest that apparently subtle differences in the onset of sexual maturation may have long-lasting implications for intersexual relationships.

Associations between father absence and age of first sexual intercourse

Children raised without a biological father in the household have earlier average ages of first sexual intercourse than children raised in father-present households. Competing theoretical perspectives have attributed this either to effects of father absence on socialization and physical maturation or to nonrandom selection of children predisposed for early sexual intercourse into father-absent households. Genetically informative analyses of the children of sister dyads (N = 1,382, aged 14-21 years) support the selection hypothesis: This association seems attributable to confounded risks, most likely genetic in origin, which correlated both with likelihood of father absence and early sexual behavior. This holds implications for environmental theories of maturation and suggests that previous research may have inadvertently overestimated the role of family structure in reproductive maturation.

The breast cancer and the environment research centers: transdisciplinary research on the role of the environment in breast cancer etiology

OBJECTIVES

We introduce and describe the Breast Cancer and the Environment Research Centers (BCERC), a research network with a transdisciplinary approach to elucidating the role of environmental factors in pubertal development as a window on breast cancer etiology. We describe the organization of four national centers integrated into the BCERC network.

DATA SOURCES

Investigators use a common conceptual framework based on multiple levels of biologic, behavioral, and social organization across the life span. The approach connects basic biologic studies with rodent models and tissue culture systems, a coordinated multicenter epidemiologic cohort study of prepubertal girls, and the integration of community members of breast cancer advocates as key members of the research team to comprise the network.

DATA EXTRACTION

Relevant literature is reviewed that describes current knowledge across levels of organization. Individual research questions and hypotheses in BCERC are driven by gaps in our knowledge that are presented at genetic, metabolic, cellular, individual, and environmental (physical and social) levels.

DATA SYNTHESIS

As data collection on the cohort, animal experiments, and analyses proceed, results will be synthesized through a transdisciplinary approach.

CONCLUSION

Center investigators are addressing a large number of specific research questions related to early pubertal onset, which is an established risk factor for breast cancer. BCERC research findings aimed at the primary prevention of breast cancer will be disseminated to the scientific community and to the public by breast cancer advocates, who have been integral members of the research process from its inception.