Monozygotic twin differences in nonshared environmental factors associated with chronotype

Barclay, Nicola L.; Eley, Thalia C.; Parsons, Michael J.; Willis, Thomas A. and Gregory, Alice M.. 2013. Monozygotic twin differences in nonshared environmental factors associated with chronotype. Journal of Biological Rhythms, 28, pp. 51-61. [Article]

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Abstract Twin studies have highlighted that a large proportion of variability in chronotype is accounted for by individual-specific environmental factors (nonshared
environmental influences). However, little research has aimed to identify specific non-shared environmental influences on chronotype. Although epidemiological
studies have shed light on possible environmental influences on chronotype, a substantial amount of research has highlighted the importance of genetic influences on exposure toward specific environments, a process termed geneenvironment correlation. It is possible that associations between the environment and chronotype are in part determined by genetics, rather than being purely environmental in origin. One way of exploring the contribution of purely non-shared environmental components on associations between chronotype and the environment is to use the monozygotic twin differences design. This design allows us to tease apart the influences of genetics and the environment to identify purely environmental components. One hundred eighty-nine monozygotic twin pairs (mean age 19.81 years, SD = 1.26, range = 18-22 years, 66.1% female) completed the Horne
and Östberg Morningness-Eveningness Questionnaire as a measure of chronotype and questionnaires assessing the following candidate non-shared environmental influences: dependent and independent negative life events, educational attainment, employment status, relationship status, deviant peers, affiliation with deviant
peers, general health, smoking, drug use, and alcohol use. Linear regression analyses indicated the presence of gene-environment correlation for the majority of associations between chronotype and candidate environmental influences. When controlling for genetic and shared environmental effects, within monozygotic twinpair
differences in chronotype were associated with within monozygotic twinpair differences in dependent negative life events (β = –0.27, p < 0.001), educational attainment (β = –0.14, p < 0.05), smoking status (β = 0.22, p < 0.01), and drug use (β = –0.16, p < 0.01). These results suggest that some of the association between these variables is purely environmental in nature. The associations between the remaining environmental variables and chronotype, however, may be intertwined with underlying genetic factors. These findings add to our understanding of
genetic and environmental mechanisms underlying the biological clock.

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Date Deposited:

21 May 2014 19:15

Last Modified:

30 Jun 2017 15:19

Peer Reviewed:

Yes, this version has been peer-reviewed.


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