Do Different Measures Tap the Same Genetic Influences? A Multi-Method Study of Activity Level in Young Twins

Activity level (AL) is a highly salient feature of child behaviour that has been linked to developmental outcome. Twin studies of parent-rated, observer-rated and mechanically assessed AL in childhood find that AL is genetically influenced. Few studies, however, consider whether different methods of assessing AL have a shared genetic etiology. Those that do, confound methods and situations. The present study examined whether actigraph and rater-based (parent, observer) measures of AL tap the same genetic influences in a sample of 312 2-year-old twin pairs. Methods were studied within the same situation, thereby controlling for situational influences on AL. The genetic correlation between actigraph and parent-rated AL in the home was 0.38, indicating modest genetic overlap between the two methods. In contrast, the correlation of genetic effects on actigraph and observer-rated AL in the laboratory was 0.95, indicating that both laboratory-based measures of AL are influenced by the same genetic effects.

Link to Abstract: http://www.ncbi.nlm.nih.gov/pubmed/19635088