utility of adoption and other family designs for elucidating components of environmental risk. However, adoption studies have certain limitations. Firstly, due to the challenges involved with accessing adoption records, these studies are not common. Secondly, biological parents, adoptive parents and adopted children are not, by any means, representative of the population: biological parents are likely to have higher rates of drug dependence while, conversely, adoptive parents are less likely to do so than the population at large. Furthermore, such designs do not negate negative prenatal influences, including prenatal drug exposure, which are more likely to be present in adoptive children than the general population.
