Genes and addiction

Drug addiction, like all psychiatric disorders, is defined solely in behavi oural terms. For example, addiction can be considered a loss of control ove r drug-taking, or compulsive drug-seeking and -taking despite horrendous co nsequences. Abnormal behaviours are a consequence of aberrant brain functio n, which means that it is a tangible goal to identify the biological underp innings of addiction. The genetic basis of addiction encompasses two broad areas of enquiry. One of these is the identification of genetic variation i n humans that partly determines susceptibility to addiction. The other is t he use of animal models to investigate the role of specific genes in mediat ing the development of addiction. Whereas recent advances in this latter ef fort are heartening, a major challenge remains: to understand how the many genes implicated in rodent models interact to yield as complex a phenotype as addiction.