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Causes to, and development of, substance abuse in adolescence

Awarded: NOK 6.0 mill.

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2012 - 2015

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-Substance use in adolescence is an important risk factor for the development of a number of adjustment difficulties in adult age. Whether or not the youth?s drug use progresses to abuse and addiction depends on several other factors. The young person?s belief in their own ability to achieve goals (' self efficacy ') is thought to be a protective factor against development of substance related difficulties, and is thus a potential target for prevention and treatment. We found, however, that a high percentage (75%) of the variation in youth ' self efficacy ' can be explained by variation in the genes. The remaining proportion of the variation (25%) was explained by cincumstances in the environment that were not shared between the twins. Tobacco smoking is a risk factor for a range of psychological and behavioral difficulties in adolescence, and we studied the relative importance of genes and environmental causes for youth?s tobacco use. Based on maternal, paternal and twins? self report we found teenagers ' smoking habits to be moderately heritable (37%). The largest amount of explained variance was due to the twins ' shared environment (56%), while environmental effects that only affected one of the twins were of minimal importance (7%). We found no significant gender differences in these estimates. The results of this study suggest that the home environment can be an active influence source of high school students ' tobacco smoking. Externalizing difficulties such as crime and drug problems in youths are related to the personality trait impulsivity. However, the causal mechanisms behind these associations have been unclear. In the data from about 800 twin pairs, we found a low association between externalizing difficulties and impulsivity. There were only weak common causal genetic and environmental links between impulsivity and externalizing difficulties. Thus, there was low support for considering impulsiveness to be a target for preventive intervention against the development of substance abuse in this study.

Drug use and abuse in youth are among the factors most strongly responsible for negative trajectories of the educational course for some youths. Even small scale drugs testing may lead to more serious drugs abuse and dependence. Studies have shown that th e development of substance use disorders (SUD) is genetically influenced. Main objectives are to go further by not only studying the relative contribution of genes and environment in the development of SUD, but to investigate the interaction (GxE) and the correlations (rGxE) between them. Hypothesis: Early onset SUD are moderately genetically influenced on average. Heavy users may be more strongly genetically influenced. However, the prevalence and influence of genes depend on the combination of family, s ocial and cultural protecting and risk factors. Method: An ongoing longitudinal twin study where participants are 2800 twins aged 12 to 18 years at the start. Twins and parents answer a survey every 2nd. year in 3 waves (waves 1-2 already completed). Twin s are interviewed at age 18, assessing lifetime DSM-IV axis I (MINI lifetime form) and II disorders (SIDP), including SUD. Drug use and abuse between 12 and 18 years is assessed by the questionnaire Substance use scale from the Monitoring the Future study . Measures of protective factors: Parenting Scale, Resilience and Youth Development of the California Healthy Kids Survey, Religious Attitudes Scale, Resilience Scale, the Ego-Resilience scale and KIDCOPE. Analyses: Gene-environment interaction analyses, controlling for rGE. Critical R&D challenges: Studying the effect of protective factors while controlling for heritability will contribute to and support results from previous research that has been pursued without this control. Applic. potential: Results will be of high value for intervention for children and adolescents with SUD and hopefully prevent later pathological development.

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