RESUMEN
OBJECTIVE: This study reports prevalences of lifetime and current alcohol, tobacco and drug use in adolescents; examines associations between substance use and a number of putative risk factors; and estimates the contribution of genetic, shared and unique environmental influences on substance use. METHOD: Substance use data were collected using the Child and Adolescent Psychiatric Assessment on a population sample of 1,412 male and female monozygotic and dizygotic twin pairs, aged 8 through 16, from the Virginia Twin Study of Adolescent Behavioral Development. RESULTS: Heritabilities were estimated to be 84% and 82% for liability to lifetime and current tobacco use, respectively. For alcohol use the role of genes and environment varied according to the context of reporting. Liability to lifetime alcohol use was estimated to be under environmental control, with 71% of the variation shared by members of a twin pair and 29% unique to individual twins. Lifetime alcohol use without the permission of a parent or guardian and current use of alcohol were predominantly explained by genetic factors (h2 = 72% and 74%). The role of genetic factors increased and that of unique environmental factors decreased with increasing severity of alcohol use. Lifetime use of any drug showed a heritability of 45%, with the shared environment accounting for 47% of the variation. Shared environmental factors explained most of the variation in marijuana use. CONCLUSIONS: Genetic factors explained a significant proportion of the variation in the use of tobacco, alcohol and other drugs. Shared environmental factors contributed significantly to lifetime alcohol use and other drug use.
Asunto(s)
Conducta del Adolescente/psicología , Consumo de Bebidas Alcohólicas , Fumar , Trastornos Relacionados con Sustancias , Adolescente , Factores de Edad , Consumo de Bebidas Alcohólicas/genética , Consumo de Bebidas Alcohólicas/psicología , Niño , Estudios de Cohortes , Familia/psicología , Femenino , Humanos , Estudios Longitudinales , Masculino , Fumar Marihuana/genética , Fumar Marihuana/psicología , Plantas Tóxicas , Religión , Factores Sexuales , Fumar/genética , Fumar/psicología , Factores Socioeconómicos , Trastornos Relacionados con Sustancias/genética , Trastornos Relacionados con Sustancias/psicología , Tabaco sin Humo , Gemelos Dicigóticos/genética , Gemelos Dicigóticos/psicología , Gemelos Monocigóticos/genética , Gemelos Monocigóticos/psicología , VirginiaRESUMEN
Although the prevalence and associated factors of smokeless tobacco (SLT) use are well-documented, there are no data on the prevalence and associated factors of SLT dependence-addiction. From a survey of 11,057 adolescents in the nonurban Southeastern United States, 3,726 reported having tried SLT, and 17% of those who had tried SLT perceived that they were addicted to it. Years of SLT use, frequency of use per day, and hours of exposure per day were strongly related to perceived addiction. Those using SLT for 1 year or longer had perceived addiction rates of 37% and were over 12 times more likely to report being addicted than were those using for less than 1 year. After controlling for level of SLT use, other factors including parental SLT use, perceived control over health, and racial-ethnic group also contributed minimally but significantly to reported SLT addiction.
Asunto(s)
Plantas Tóxicas , Autoevaluación (Psicología) , Tabaquismo/epidemiología , Tabaco sin Humo/efectos adversos , Adolescente , Actitud Frente a la Salud , Intervalos de Confianza , Femenino , Humanos , Modelos Logísticos , Masculino , Oportunidad Relativa , Muestreo , Sudeste de Estados Unidos/epidemiología , Tabaquismo/etnología , Tabaquismo/psicologíaRESUMEN
This study was designed to examine the morphologic properties of the masseter muscle in individuals with vertical maxillary excess (VME). The deep surface of the anterior aspect of the superficial masseter was biopsied in nine patients at the time of corrective surgery. Individual muscle fibers were classified as slow-twitch-oxidative (SO), fast-twitch-oxidative-glycolytic (FOG), or fast-twitch-glycolytic (FG) based on staining characteristics using a battery of histochemical procedures. Most patients had normal tissue, although there were considerable differences in size and distribution of the three fiber types. Generally, SO fibers were the largest and most prevalent type of fiber. Two individuals, however, demonstrated evidence of muscle pathology that primarily affected the FG fiber population. Histochemical evidence of muscle pathology has not previously been reported in patients with VME, and the pattern of SO dominance observed in these patients may be different from the distribution that would be seen in the masseter of a person free of craniofacial deformities.