Estimation of individual genetic and environmental profiles in longitudinal designs.

Explored through simulation of longitudinal twin designs how many measures are needed at each time point to estimate reliably individual genetic and nongenetic profiles and whether the answer to this question depends on the magnitude of the genetic and environmental autocorrelations across time. Individual estimates of factor scores were reliably obtained. Decomposition of univariate, and to a lesser extent of bivariate, phenotypic time series may yield estimates of individual additive genetic and environmental factor scores that are intercorrelated. The magnitude of these correlations is dependent on the autocorrelation structure of the underlying series, but to obtain completely independent estimates of genetic and environmental individual profiles, as least 3 measured indicators are needed at each point in time.