genetic factors. Although this criticism is not entirely founded on the part of either field, methodological and ideological differences between these respective fields meant that genetic and environmental influences were traditionally studied in isolation. More recently, there has been recognition on the part of both of these fields that both genetic and environmental influences are critical components to developmental outcome and that it is far more fruitful to attempt to understand how these factors come together to impact psychological outcomes than to argue about which one is more important. As Kendler and Eaves argued in their article on the joint effect of genes and environments, published more than two decades ago: It is our conviction that a complete understanding of the etiology of most psychiatric disorders will require an understanding of the relevant genetic risk factors, the relevant environmental risk factors, and the ways in which these two risk factors interact. Such understanding will only arise from research in which the important environmental variables are measured in a genetically informative design. Such research will require a synthesis of research traditions within psychiatry that have often been at odds with one another in the past. This interaction between the research tradition
