A longitudinal study of twins from birth to adulthood
AbstractTemperamental variation in infancy was the starting point for this longitudinal study of twins followed from
birth to adulthood. The influence of early individuality on later development was a research question in the
follow-ups, and by choosing twins as a group, it was possible to uncover the effect of environmental and
genetic factors at the different ages. Developmental psychopathology turned out to be a relevant framework,
where mental health and well-being are seen as the result of a continuous transaction between geneticallybased
individuality and a changing and varying environment (Maughan & Rutter, 2008). The twin method
was an adequate tool to gain a better understanding of these processes. The overall clear message from the
study is that whereas heritability of temperament can be seen from infancy on, environmental factors are of
crucial importance for an understanding of mental development and health, but the effect of environmental
factors probably varies a great deal in dependency upon the genetic disposition of the person.
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