Many of the traits in this study are mouse models of behavioral predictors of substance abuse in humans. These include stress, anxiety, novelty seeking, risk taking, impulsivity, pain sensitivity and despair. These measures were integrated with assays assessing effects of drugs such as sensitization, physiological response and withdrawal. Together these data enable a multi-dimensional genetic analysis, allowing detection of genes and genetic loci that are associated simultaneously with predisposition and drug response. This is an en masse approach to examining the relations among predisposing behavior and drug self-administration recently showed by Belin et al. (2008). Factors that predispose an individual to addiction have been grouped into three categories—environmental factors, drug-induced neural changes and genetic factors (Kreek & LaForge 2007). However, there is much interplay among them. For example, genetic variation may influence response to environmental effects in the same way as it influences drug-induced neural changes as a pleiotropic effect. Elucidating the mechanisms by which susceptibility traits relate to addiction can be achieved through continual aggregation of molecular, physiological, morphological and behavioral data in a mouse genetic reference population (Plomin et al. 1991).
