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Co-Twin Dependence Modifies Heritability of Abstinence and Alcohol Use: A Population-Based Study of Finnish Twins

Published online by Cambridge University Press:  21 February 2012

Varpu Penninkilampi-Kerola ,
Jaakko Kaprio ,
Irma Moilanen  and
Richard J. Rose
Varpu Penninkilampi-Kerola*
Affiliation:
Department of Public Health, University of Helsinki, Helsinki, Finland; Clinic of Child Psychiatry, University and University Hospital of Oulu, Oulu, Finland. [email protected]
Jaakko Kaprio
Affiliation:
Department of Public Health, University of Helsinki, Helsinki, Finland; Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland.
Irma Moilanen
Affiliation:
Clinic of Child Psychiatry, University and University Hospital of Oulu, Oulu, Finland.
Richard J. Rose
Affiliation:
Department of Public Health, University of Helsinki, Helsinki, Finland; Department of Psychology, Indiana University, Indiana, United States of America.
*
*Address for correspondence: Varpu Penninkilampi-Kerola, M.Ed., Clinic of Child Psychiatry, University of Oulu, PO Box 26, FIN-90029 OYS, Finland.

Abstract

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The role of co-twin dependence (twins' closeness or reliance on the co-twin) was examined as a moderator of genetic and environmental influences on alcohol use in adolescence and early adulthood in a large longitudinal population-based study of Finnish twins (FinnTwin16). The associations between co-twin dependence and alcohol use were studied first at an individual level in adolescence (n = 3362) and early adulthood (n = 2912). Then, maximum likelihood models were fit to the two waves of data from same-sex twin pairs to assess the differences and changes in genetic and environmental influences on alcohol use (abstinence, drinking frequency, intoxication frequency); N = 1342 pairs in adolescence, and N = 1078 pairs in early adulthood. Overall, no significant associations were found between co-twin dependence and individual alcohol use. However, co-twin dependence importantly modulated genetic effects on drinking habits, especially in adolescence, but also in early adulthood. Co-twin–dependent twins reported greater similarity in their alcohol-related behavior across all alcohol-use measures at both time points, and the role of genes and environments varied according to co-twin dependence. Shared environmental factors explained most of the variation in drinking among co- twin–dependent twins in adolescence and contributed to drinking to intoxication during early adulthood. In contrast, among co-twin–independent twin pairs, genetic variance contributed significantly to all alcohol-use measures at both time-points. An interdependent sibling relationship is an important modifier of drinking habits, and it appears to reduce the impact of inherited liabilities on alcohol-related behavior especially in adolescence.

Type
Articles
Information
Twin Research and Human Genetics , Volume 8 , Issue 3 , 01 June 2005 , pp. 232 - 244
Copyright
Copyright © Cambridge University Press 2005