It is likely that this distinction also reflects differences in training and emphasis across different fields. The most cutting-edge genetic strategies at any given point, though they have changed drastically and rapidly over the past several decades, have generally involved athe-oretical methods for gene identification (Neale et al. 2008). This was true of early linkage analyses, where ~400 to 1,000 markers were scanned across the genome to search for chromosomal regions that were shared by affected family members, suggesting there may be a gene in that region that harbored risk for the particular outcome under study. This allowed geneticists to search for genes without having to know anything about the underlying biology, with the ideas that the identification of risk genes would be informative as to etiological processes and that our understanding of the biology of most psychiatric conditions is limited. Although it is now recognized that linkage studies were underpowered to detect genes of small effect, such as those now thought to be operating in psychiatric conditions, this atheoretical approach was retained in the next generation of gene-finding methods
