However, that role is likely to be complex, involving multiple genes and an interaction with environmental factors. To increase the likelihood of identifying these complex genetic influences, the scientists recommended that researchers use a variety of approaches for locating candidate genes, including sib-pair analysis and association studies. Sib-pair analysis is the most commonly used approach in disorders such as drug abuse that involve more than one gene. In sib-pair analysis, researchers compare the genetic material of sibling pairs who abuse drugs with the genetic material of sibling pairs who do not abuse drugs in order to identify candidate genes that may contribute to drug abuse. After locating a candidate gene, scientists clone the gene and then study it to determine how it contributes to the disorder.
Association studies involve an approach that is opposite to the approach used in sib-pair analysis.
In association studies of drug abuse, researchers hypothesize from what is known about the biochemistry of addiction that a particular gene with known location and function contributes to drug abuse. The researchers then determine whether drug abusers have a different version of this gene than nondrug abusers. Researchers who are approved by CIDR will be able to send blood samples to the Center for free analyses. CIDR was established in 1996 as a joint effort by eight of the National Institutes of Health, including NIDA, to provide a central location where genetic analyses could be performed more rapidly, with greater consistency, and at lower cost than if investigators were to perform their own analyses. NIDA is encouraging researchers conducting animal studies of possible vulnerability genes to include not only those animals that have been traditionally used in drug addiction research, such as mice and rats, but also animals that rarely have been used in this field, such as fruit flies, worms, and zebrafish.