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Recent opposing trends towards earlier physical maturation and later social maturation present a conundrum of apparent biologicalsocial mismatch. Here we use life history analysis from evolutionary ecology to identify forces that drive these shifts. Together with findings in developmental science, our life history analysis indicates that adolescence is a distinctive period for biological embedding of culture. Ethnographic evidence shows that mass education is a novel feature of the globalizing cultural configurations of adolescence, which are driven by transformations in labour, livelihood and lifestyle. Evaluation of the life history trade-offs and sociocultural ecologies that are experienced by adolescents may offer a practical basis for enhancing their development., Author(s): Carol M. Worthman (corresponding author) [1]; Kathy Trang [1] For humans, the second decade of life is often described as a period of turmoil roiled by biological and sociocultural [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jada.2009.08.016 Byline: Nicole I. Larson, Dianne Neumark-Sztainer, Mary Story Abstract: Cross-sectional research has found that dieting during adolesence and the use of extreme weight control behaviors are related to less healthful dietary patterns; however, little is known regarding longitudinal relationships. Article History: Accepted 5 June 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jada.2009.07.004 Byline: Ann M. Albertson, Douglas Thompson, Debra L. Franko, Norton M. Holschuh, Robert Bauserman, Bruce A. Barton Abstract: Cereal consumption is a common dietary behavior that has been associated with positive health outcomes. The objective of this study was to examine prospective associations between cereal intake in childhood and percent body fat, waist-to-hip ratio, lipid levels, and physical activity during late adolescence. In this longitudinal investigation (data collected 1987-1997), data were analyzed for the 2,379 girls who participated in the 10-year National Heart, Lung, and Blood Institute Growth and Health Study. The cumulative percent of days that each girl consumed cereal during childhood (based on 3-day food diaries collected during six study visits between ages 11.5 and 18.6 years) was examined in relation to percent body fat, waist-to-hip ratio, lipid levels, and physical activity measured at age 18.6 years. Results indicated that nearly all girls (90.1%) reported eating cereal and 18.7% reported eating cereal on half or more of the days reported in the food diaries. Girls who ate cereal on a greater percentage of days during childhood had lower percent body fat and total cholesterol, and were more likely to exhibit high levels of physical activity and less television viewing during Study Year 10 (P values<0.05). Further research should explore lifestyle issues related to cereal consumption. Article History: Accepted 30 March 2009

Adolescence is characterized by increased vulnerability to developing neuropsychiatric disorders and involves a period of prefrontal cortical dendritic refinement and synaptic pruning that culminates in cytoskeletal stabilization in adulthood. The Abl-related gene (Arg) acts through p190RhoGAP to inhibit the RhoA GTPase and stabilize cortical dendritic arbors beginning in adolescence. Cortical axons, dendrites, and synapses develop normally in Arg-deficient ([arg.sup.-/-]) mice, but adult dendrites destabilize and regress; thus, [arg.sup.-/-] mice present a model of adolescent-onset dendritic simplification. We show that [arg.sup.-/-] mice are impaired in a reversal task and that deficits are grossly exacerbated by low-dose cocaine administration. Although ventral prefrontal dopamine D2 receptor levels predict 'perseverative' error counts in wild-type mice, no such relationship is found in [arg.sup.-/-] mice. Moreover, [arg.sup.-/-] mice are insensitive to the disruptive effects of the D2/D3 antagonist haloperidol in reversal but show normal sensitivity to its locomotor-depressant actions. Arg deficiency and orbitofrontal cortical Arg inhibition via STI-571 infusion also enhance the psychomotor stimulant actions of cocaine. These findings provide evidence that stabilization of dendritic structure beginning in adolescence is critical for the development of adaptive and flexible behavior after cocaine exposure. D2 | orbital cortex | prefrontal cortex | reversal learning

Methodological issues relevant to magnetic resonance imaging studies of brain anatomy are discussed along with the findings on the neuroanatomic changes during childhood and adolescence. The development of the brain is also discussed.

It is now recognized that extensive maturational changes take place in the human brain during adolescence, and that the trajectories of these changes are best studied longitudinally. We report the first longitudinal study of the adolescent decline in non-rapid eye movement (NREM) delta (1-4 Hz) and theta (4-8 Hz) EEG. Delta and theta are the homeostatic frequencies of human sleep. We recorded sleep EEG in 9- and 12-year-old cohorts twice yearly over a 5-year period. Delta power density (PD) was unchanged between age 9 and 11 years and then fell precipitously, decreasing by 66% between age 11 and 16.5 years (P < .000001). The decline in theta PD began significantly earlier than that in delta PD and also was very steep (by 60%) between age 11 and 16.5 years (P < .000001). These data suggest that age 11-16.5 years is a critically important maturational period for the brain processes that underlie homeostatic NREM EEG, a finding not suggested in previous cross-sectional data. We hypothesize that these EEG changes reflect synaptic pruning. Comparing our data with published longitudinal declines in MRI-estimated cortical thickness suggests the theta age curve parallels the earlier maturational thinning in 3-layer cortex, whereas the delta curve tracks the later changes in 5-layer cortex. This comparison also reveals that adolescent declines in NREM delta and theta are substantially larger than decreases in cortical thickness (>60% vs. adolescence | brain development | EEG | sleep

This investigation evaluates the performance of juvenile stature (from tibia and radius lengths) and body mass (from breadth of the femoral distal metaphysis) prediction equations based on the Denver Growth Study sample (Ruff C. 2007. Am J Phys Anthropol 133 698-716). The sample used here for evaluation is an independent sample of juveniles brought to the Franklin County (Ohio) Coroner in 1990-1991. The Ohio sample differs somewhat from the Denver reference sample: it includes ~25% African-Americans (rather than all European-Americans), a significant number of right limb bones were measured (rather than all left side), it includes a wider range of economic statuses and it includes individuals who died from disease and trauma. As such the composition and measures of the Ohio sample correspond more generally to that seen in skeletal samples so that the accuracy of the estimates from the present sample should approach those found in practical applications of these methods. Results indicate that both juvenile body mass and stature are estimated relatively accurately. Accuracy of body mass estimates for 1-13-year-old juveniles is similar for African-American and European-American males and females. The least accurate estimates are for individuals in the 8-13 years age class (excluding individuals with body mass indices greater than the age specific 95th percentile): n = 9, [+ or -] 2.9 kg, 95% confidence interval 1.4-4.4 kg. Accuracy of stature estimates for 1-17-year-old juveniles is comparable for the tibia and radius and, as with body mass estimates, are similar for African-American and European-American males and females. For combined age, sex, and ancestry groups average accuracies are in the [+ or -] 3.5 to [+ or -] 6.5 cm range. Some limitations of the methods are discussed. KEY WORDS juvenile; stature; body mass; accuracy; bias

Although there are some studies documenting structural brain changes during late adolescence, there are few showing functional brain changes over this period in humans. Of special interest would be functional changes in the medial frontal cortex that reflect response monitoring. In order to examine such age-related differences, the authors analyzed event-related potentials following errors in a visual flanker task and a go/no-go task in adolescent males, 15-16 and 18-20 years old. Response times and accuracy were comparable between groups on each task, but the younger group made more go/no-go errors, suggesting this task was more difficult. Error-related negativity, thought to be generated in the anterior cingulate cortex (ACC), had greater amplitude for the older adolescents on both tasks; thus the increased errors are not simply due to performance level differences. Results from this study suggest that the ACC, which supports response monitoring, is late to mature due to age-related structural or neurochemical changes. Keywords: adolescence, error monitoring, anterior cingulate, ERP, ERN

Size at birth and early postnatal growth are determinants of adult height and BMI. The aim of this study was to evaluate the effect of birth weight on body composition and fat distribution in a group of Spanish adolescents. Current body composition was assessed by both skinfold thickness and dual X-ray absorptiometry in 234 adolescents born at term (140 girls and 94 boys), now aged 13-18 y and living in the city of Zaragoza. Relative fat distribution was estimated using the ratio of the subscapular to triceps skinfolds (S:T). Birth weight and gestational age were assessed by a questionnaire. Birth weight was inversely associated with the S:T ratio (P < 0.05) in boys and directly associated with bone mass (P < 0.01) and fat-free mass (P < 0.05) in girls. This association was independent of factors such as age, Tanner stage, gestational age, socioeconomic status, physical activity, and height. In conclusion, our data support the hypothesis that impaired fetal growth, measured by birth weight, may be related to central fat distribution in boys and decreased bone and fat-free mass in girls. KEY WORDS: * birth weight * body composition * adolescence

A theoretical framework is proposed for studying minority young men's involvement with their babies that combines the integrative model of minority youth development and a life course developmental perspective with Lamb's revised four-factor model of father involvement. This framework posits a relationship between demographic and family background variables (such as education, employment, income, and family of origin) and fatherhood outcomes moderated by personal characteristics (such as sex-role ideology, acculturation, risk taking, and alienation) and mediated by definitions of fatherhood, life priorities normative for the culture under study, and sexual behavior. Once there is an acknowledged infant, a father's involvement is influenced by child characteristics, perceived fathering competence, social support, and quality of the relationship with the mother., While men bear half of the biological responsibility for conception, until the late 1970s, they had been largely ignored in the discourse on pregnancy and child care. In the last [...]

In order to contribute to a more comprehensive model of speech motor development, we examined the movement trajectories of the upper lip, lower lip, and jaw to determine (a) if there are changes in articulatory motor control in late adolescence; (b) if there are sex differences during this developmental period, perhaps related to differences in craniofocial growth rates; (c) if control of jaw motion is adultlike earlier than control of the upper and lower lip; and (d) if control of spatial and temporal aspects of articulatory movement co-develop in adolescence. Participants were 12-, 14-, and 16-year-olds, and young adults (mean age 21.2 years), with 15 males and 15 females per group. A measure reflecting spatiotemporal consistency in trajectory formation for repeated productions of a phrase was calculated for the upper lip, lower lip, and jaw movements. Overall trajectory variability was higher for adolescents compared to young adults. Jaw trajectories were less variable than upper lip or lower lip trajectories, but all effectors showed parallel decreases in variability as age increased, suggesting that control of jaw movement does not reach adult performance before control of the lips. Separate temporal and spatial measures revealed that adolescents had significantly longer movement durations, lower velocities, smaller displacements, and greater variability on these measures than young adults. There were no sex differences on any measure examined, suggesting that peripheral growth factors do not account for this protracted developmental time course. These results provide initial evidence of significant changes in speech motor control processes during adolescence. KEY WORDS: speech production, motor control, kinematics, development, adolescence, The term "puberty" refers to the biological changes that occur during adolescence. It is characterized by dramatic cognitive development, physical growth, changes in body composition, and full maturation of the [...]

Compared to adults, children&apos;s speech production measures sometimes show higher trial-to-trial variability in both kinematic and acoustic analyses. A reasonable hypothesis is that this variability reflects variations in neural drive to muscles as the developing system explores different solutions to achieving vocal tract goals. We investigated that hypothesis in the present study by analyzing EMG waveforms produced across repetitions of a phrase spoken by 7-year-olds, 12-year-olds, and young adults. The EMG waveforms recorded via surface electrodes at upper lip sites were clearly modulated in a consistent manner corresponding to lip closure for the bilabial consonants in the utterance. Thus we were able to analyze the amplitude envelope of the rectified EMG with a phrase-level variability index previously used with kinematic data. Both the 7- and 12-year-old children were significantly more variable on repeated productions than the young adults. These results support the idea that children are using varying combinations of muscle activity to achieve phonetic goals. Even at age 12 years, these children were not adult-like in their performance. These and earlier kinematic studies of the oral motor system suggest that children retain their flexibility, employing more degrees of freedom than adults, to dynamically control lip aperture during speech. This strategy is adaptive given the many neurophysiological and biomechanical changes that occur during the transition from adolescence to adulthood. KEY WORDS: speech development, lip muscles, EMG, speech motor conlrol, performance variability., Variability in performance is a hallmark of the early learning process for any complex motor skill (Schmidt & Lee, 1999, p. 360), so it is not surprising to find that [...]

Physiologic adaptation to the high calcium demand during pregnancy and lactation may be different in adolescents than in adults, particularly at low calcium intake. The aim of this cross-sectional study was to compare biochemical markers of calcium and bone metabolism between adolescent (14-19 y) and adult (21-35 y) women with calcium intake ~500 mg/d, in three different physiologic states, i.e., control (nonpregnant, nonlactating; NPNL), pregnant and lactating. Markers of calcium metabolism [serum Ca, P and intact parathyroid hormone (iPTH); urinary Ca and P] and of bone turnover [urinary deoxypyridinoline (D-Pyr) and plasma bone alkaline phosphatase (BAP)] were measured in NPNL (adolescents, n = 12 and adults, n = 25), pregnant (adolescents, n = 30 and adults, n = 36) and lactating (adolescents, n = 19 and adults, n = 26) women. In the NPNL women, iPTH, D-Pyr and BAP were higher (P < 0.001) and urinary Ca was lower (P < 0.001) in adolescents than in adults. Serum iPTH was higher (P < 0.001) and urinary Ca was lower (P < 0.01) in adolescents than in adults also in pregnancy and lactation. Compared with NPNL women, serum Ca decreased (P < 0.001) with pregnancy in adolescents but not in adults. The increase in D-Pyr with pregnancy and lactation was very pronounced in adults (~130%, P < 0.001) but less in adolescents ( KEY WORDS: * calcium * adolescence * pregnancy * lactation * bone turnover

Sexual desire is properly seen as produced by sociocultural, biological, and sociopolitical factors. The authors present a methodological approach to same-sex sexuality, sexual maturation, and sexual dysfunction.

Research is presented on the onset of growth spurt among adolescent Japanese based on data accumulated since 1915. Timing of maximum growth has decreased for both sexes, with the onset for growth spurts among boys decreasing and for girls remaining mostly constant, occurring generally between 6 and 8 years of age.

Research on the growth factors for males and females is measured using schoolchildren between the ages of 7 and 14 in Jena, Germany. Sex difference plays little role in indexes during childhood, however marked differences did occur during adolescent growth spurts when females developed broader hips and shorter legs than the males.

Research on monozygotic twins is presented, with the purpose of assessing age-related changes by analyzing physical growth and running performance. Issues discussed include the genetic components involved in running skills, specifically performances in endurance; and the possible genotype contributions effecting the growth of children over a period of time.

A literature review of the data on dietary habits, food consumption and nutritional status of adolescents of Southern European countries was performed. Snacking seems to be less frequent and the frequency of eating out in fast food restaurants is much lower than in the USA and in some Nordic Countries. A nutrient pattern rich in total fat (around 40% of the energy intake), in saturated fatty acids (around 13% of the energy intake) and mainly in monounsaturated fatty acids (17-19% of the energy intake), due to a high consumption of olive oil, is often observed in Spanish and Greek adolescents. In Portugal, the percentage of the energy provided by fat is relatively low (31-33% of the energy intake) and in Italy the situation is intermediate regarding total fat, but the intake of olive oil is also high. This means that two important characteristics of the Mediterranean diet, a low consumption of saturated fatty acids and a high intake of carbohydrates have been lost. Regarding micronutrients, there seems to exist a risk of deficiency, particularly for calcium, iron and zinc. The prevalence of overweight/obesity is high, around 15-25%, being higher than in the Nordic countries but lower than in the USA. There is no clear indication of trends, due to the different methods and criteria used to define obesity. The serum cholesterol levels of adolescents has increased during the last two decades in Spain, Greece and Italy, and nowadays are similar to those in the USA, but still lower than in the Nordic countries. In Portuguese adolescents, the cholesterol levels seem to be lower, but the situation is not well known. Descriptors: adolescents; dietary patterns; anthropometry; serum lipids; Southern European countries, Introduction Adolescents are vulnerable from the nutritional point of view, due to their peculiar life style and dietary habits and to their high energy and nutrient requirements (Duyer, 1981; Anderson, [...]

Objective: To describe food habits and dietary intakes of athletic and non-athletic adolescents in Switzerland. Setting: College, high schools and professional centers in the Swiss canton of Vaud. Method: A total of 3540 subjects aged 9-19y answered a self-reported anonymous questionnaire to assess lifestyles, physical plus sports activity and food habits. Within this sample, a subgroup of 246 subjects aged 11-15 also participated in an in-depth ancillary study including a 3 day dietary record completed by an interview with a dietician. Results: More boys than girls reported engaging in regular sports activities (P Conclusions: Athletic adolescents display healthier food habits than non-athletic adolescents: this result supports the idea that healthy behavior tends to cluster and suggests that prevention programs among this age group should target simultaneously both sports activity and food habits. Sponsorship: Service of Sports and Physical Education of the Swiss canton of Vaud, Federal Sports School of Macolin (Switzerland). Descriptors: adolescence; physical activity; sports activity; food habits, Introduction Energy needs are high during adolescence and include three major components: the energetic cost of basal metabolic rate, the cost of daily growth and the cost of physical activity, [...]

Dietary needs during adolescence lack specific definitions, and most evidence is derived from indirect indications. The data on dietary needs for energy and proteins are mainly extrapolated from subjects in other age-classes. Lipids and carbohydrates are being progressively considered for preventive purposes since the qualitative distribution of saturated and unsaturated fats and slowly and rapidly absorbed carbohydrates, respectively, seems to be associated with metabolic index predictors of degenerative disorders in later stages of life. The recent results of multicentric autoptic studies in young people from the US indicate that the lipoprotein status of the second decade of life is associated with the first raised arterial lesions in the third decade. The evidence of these links needs further confirmation from ongoing surveys. We must recognize that adolescence is a critical period of life, and food fads may deeply change the dietary habits acquired within the familiar group. As nutritionists, we may suggest that all adolescents should be supplied with nutritional support in terms of education, maybe at school, to improve their knowledge of nutrition. Descriptors: adolescence; dietary habits; dietary recommendations; prevention, Introduction Adolescence is an intense anabolic period. Indicated dietary allowances for macronutrients in this period should cover both growth processes and preventive purposes. In this perspective, the quality of the [...]

Skeletal growth and changes in body composition during growth present important variations; body mass index and lean body mass related to age show important gender differences. The process of ossification is developed in two different ways, endochondral and intramembraneous. The former is characterised by the formation of bone from growth cartilage. Intramembraneous ossification is characterised by the formation of bone from a mesenchymal structure, as occurs with the flat bones of the skull. During childhood and adolescence and up to the acquisition of adult stature, two phenomenons are produced simultaneously: the synthesis of new bone from growth cartilage due to the process of endochondral ossificaion, and modeling--remodeling of previously synthetised bone. Bone growth and mineralisation of its extracellular matrix are simultaneous phenomenons, the final result being the acquisition and maintenance of body bone mass. A positive calcium balance is necessary during adolescence in order to achieve the maximum peak of bone mass and even with the termination of longitudinal growth of bone, the process of mineralisation can last a further 4 years. Childhood and adolescence are the period of life in which the peak of bone mass must be achieved, and if during this time this does not happen there will be a greater risk for the later development of osteoporosis. Regulation of bone mass is a polygenic process and during recent years studies have been centred on the receptor genes of vitamin D and estrogens. A maximum calcium retention during adolescence may influence the achievement of a high peak of bone mass but at a certain level of calcium intake the calcium retention reaches a plateau. The expression of grams of hydroxyapatite per square centimetre has been used clinically, or expressed in volume as g/cm3. From birth until 3 years, the increase represents approximately 30% of the total increase, from 3 years until the beginning of pubertal development the increase is 20%. During pubertal development there is an increase of 3040% and from the end of growth until the age of 21 years there is an increase of 15-20%. Both prepubertal boys and girls show a progressive increase of leptin levels during the years prior to the onset of puberty and until Tanner&apos;s stage 11 and higher levels are observed in girls in this period, possibly in relation to their earlier onset of puberty. This increase of leptin in girls during pubertal development suggests that leptin may be a link between adipose tissue and puberty. Descriptors: adolescence; skeletal growth; bone mass; leptin, Introduction Normal somatic development during adolescence is characterized by rapid growth in height and weight, changes in tissues and body composition, changes in hormonal regulatory systems and development of primary [...]

New regression equations for estimating the basal metabolic rate (BMR) in 10- to 15-year-old children were derived by including pubertal stages into the equations. The mixed-longitudinal study, sponsored by Lausanne, Switzerland-based Nestle Foundation, used a sample of 165 school children in Oxford, England. In either gender, weight was found to be the most important factor in the equations. Overall, the inclusion of pubertal stage only resulted in marginal improvements to the estimated BMR.

Did the first hominids have a short developmental period similar to that of the great apes or a longer period closer to that of modern humans? Evidence from studies on dental and facial growth favors the first point of view. Additional evidence presented in this report is provided by a morphogenetic analysis of the lower limb. Some morphological modifications undergone by the human femur during infantile and adolescent growth are shown to be excellent markers of different developmental stages. The angular remodelling of the femoral diaphysis, which results in femoral bicondylar angle, is a marker of infancy, while the reshaping of the distal femoral epiphysis is a marker of adolescence. This reshaping of the bony epiphysis consists of the strong projection of the external lip of the femoral trochlea, the increase of the radius of curvature of the external condyle, and the anteroposterior lengthening of the whole epiphysis. The growth spurt in linear dimensions of the femur, characteristic of human adolescence, is shown to be associated with qualitative changes of the distal femoral epiphysis engendered by the late closure of the distal epiphysis. The femur of the first hominids (Australopithecus afarensis) shows only features of infantile growth, whereas characters of both precocious and later growth are typical of later hominids (Homo). The absence of the derived epiphyseal features in Australopithecus would be linked to their early epiphyseal closure and short adolescent growth period; their presence in Homo would have been promoted by their delayed epiphyseal closure and prolonged adolescent growth period. The transition from Australopithecus to Homo appears to have involved a heterochronic process of time hypermorphosis (Gould, [1977], Ontogeny and Phylogeny [Cambridge: Harvard University Press]) in which the size of the femur increases, the epiphysis is modified, and the period of peripubertal growth is prolonged. The shape of the distal epiphyses of KNM-WT 15000, an immature Homo erectus (Brown et al. [1985] Nature 316:788-792), lies clearly within the range of modern human adolescents. In contradiction to Smith's ([1993] in A. Walker and R. Leakey [eds.]: The Nariokotome Homo erectus Skeleton [Cambridge: Harvard University Press], pp. 195-220) hypothetical reconstruction of life span of Homo erectus, we infer that a growth spurt had begun with Homo erectus but was probably less pronounced and of shorter duration than in modern humans. Our findings on the femur are consistent with studies of the growth on the hominid pelvis (Berge [1996] in LF Marcus, M Corti, A Loy, G Naylor, and DE Slice [eds.]: Advances in Morphometrics [Chicago: Plenum Publishing Corp.], pp. 441-448). It is suggested that the lengthening of the adolescent growth period, from Australopithecus to Homo, would have been also associated with the shape changes of the pelvis and with the lengthening of the lower limbs. KEY WORDS femur; epiphysis; development; heterochrony; human paleontology