1. ¹Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, Bronx, NY, USA
2. ²Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA

Correspondence: N Hiroi, PhD, Laboratory of Molecular Psychobiology, Department of Psychiatry and Behavioral Sciences, Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA. E-mail: hiroi@aecom.yu.edu

Received 7 September 2004; Revised 19 October 2004; Accepted 26 October 2004; Published online 7 December 2004.

Abstract

Despite what is often believed, the majority of those who experiment with substances with a dependence potential do not develop dependence. However, there is a subpopulation of users that easily becomes dependent on substances, and these individuals exhibit pre-existing comorbid traits, including novelty seeking and antisocial behavior. There appears to be a genetic basis for the susceptibility to dependence and these comorbid traits. Animal studies have identified specific genes that can alter susceptibility to dependence and response to novelty. The mechanisms underlying the genetic susceptibility to dependence and response to novelty are complex, but genetic susceptibility plays a significant role in the transition from substance use to dependence and from chronic use to addiction. We discuss two models to explain how genetic variations alter dependence susceptibility. Identification of the specific genes involved in these processes would help to identify individuals that are vulnerable to dependence/addiction and to devise novel treatment strategies.