OBJECTIVE To determine the contributions of genetic and environmental influences to variation in self-report of obsessive-compulsive (OC) symptoms in a population-based twin sample of adolescent boys and girls. METHOD Self-report ratings on the eight-item Youth Self-Report Obsessive-Compulsive Scale were collected in Dutch mono- and dizygotic twin pairs who participated at age 12 (N = 746 twi...

OBJECTIVE To study the prevalence of snus use and of smoking among Swedish schoolchildren from 1989 to 2003. DESIGN Surveys conducted by the Swedish Council for Information on Alcohol and Other Drugs. SETTING All of Sweden. SUBJECTS 84,472 boys and girls age 15-16 years. MAIN OUTCOME MEASURES Subjects are classified as non-smokers, occasional smokers, and regular smokers, and into three...

Good theoretical values for vital capacity (VCt) can be used to calculate a VC/VCt ratio which remains constant for a given individual subject throughout different growth periods. This longitudinal study on 27 boys was performed in order to determine whether a single equation was accurate throughout the growth of boys. The mean values of VC/VCt were also compared for the beginning and end of th...

BACKGROUND Infection with human papillomavirus (HPV) and diseases caused by HPV are common in boys and men. We report on the safety of a quadrivalent vaccine (active against HPV types 6, 11, 16, and 18) and on its efficacy in preventing the development of external genital lesions and anogenital HPV infection in boys and men. METHODS We enrolled 4065 healthy boys and men 16 to 26 years of age,...

The purpose of this paper is to examine patterns of attainment of boys and girls at different stages of their secondary education and to investigate factors that may affect pupil outcomes. We employ a national dataset of matched examination results, recently released by the Department for Education and Skills, which includes the results of the cohort of pupils who sat Key Stage 3 exams at age 1...

This paper presents fat mass centile charts for Brazilian youth and investigates the roles of socioeconomic status and physical fitness (PF) on fat mass (FM) development. Two northeast Brazilian samples were used: a cross-sectional sample of 3659 (1921 girls) aged 8 to 16 years and a mixed-longitudinal series of cohorts (8-10, 10-12, 12-14, 14-16 years) with 250 boys and 250 girls. A measure of...