Hierarchical clustering is most conveniently limited to data from individual genes. Large 500k SNP datasets provide substantial limitations based on computer time. When we examine data from several genes using this approach in pools from a single racial/ethnic background, we can identify relatively clear patterns of separation of data from pools containing substance dependent individuals from pools containing control individuals. These hierarchical clustering approaches are independent of the principal analyses noted above. These results reassure us that modest association signals can be identified in many of these addiction-associated genes using a variety of different statistical approaches.
