Do Non-shared Environmental Influences Persist Over Time? An Examination of Days and Minutes
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Non-shared environmental influences show only minimal stability over time prior to adulthood. The long assessment lags (typically 3–5 years) that characterize most longitudinal twin studies, however, make it difficult to interpret these results. To more rigorously evaluate non-shared environmental stability prior to adulthood, we fitted biometric correlated factors models to (1) seven consecutive days of self-reported negative and positive affect in 239 twin pairs aged 16–25 years and (2) seven consecutive minutes of observer rated warmth and control in 687 twin pairs aged 6–10 years. We then empirically examined patterns of etiologic stability over time using a mixed effects analog to the one-way ANOVA. Genetic and shared environmental correlations were found to be highly stable over both days and minutes. By contrast, non-shared environmental correlations decreased monotonically with increasing lag length, and moreover, were small-to moderate in magnitude when examining intervals longer than a few minutes. Such findings imply that the non-shared environment may be comprised primarily of transient and idiosyncratic effects prior to adulthood.
KeywordsNon-shared environment Stability Genetic
This study was supported by R01-MH081813 and R01-MH082054 from the National Institute of Mental Health (NIMH) and by R01-HD066040 from the Eunice Kennedy Shriver National Institute for Child Health and Human Development (NICHD). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIMH, the NICHD, or the National Institutes of Health. The authors thank all participating twins and their families for making this work possible.
Conflict of Interest
S. Alexandra Burt, Ashlea M. Klahr and Kelly L. Klump declare that they have no conflict of interest.
Human and Animal Rights
Assessment and recruitment procedures for both studies were approved by the Michigan State University IRB, and were performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.
Informed consent (and when applicable, informed assent) was obtained from all participants.
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