Increasing evidence suggests that individual differences in DD are associated with liability to addiction and comorbid impulse control disorders. Human studies using various DD procedures have demonstrated that addicted individuals show a strong tendency to discount delayed rewards (Perry and Carroll 2008; de Wit 2009), and animal studies have shown an association between DD and the propensity to substance dependence such as alcohol preference and rates of cocaine self-administration (Perry and Carroll 2008; Verdejo-Garcia et al. 2008). It should be noted, however, that although the association between DD and different aspects of addictive behaviors is well established, the direction of causation remains unclear: this association can arise both due to pre-existing cognitive deficits leading to addiction and due to chronic drug exposure causing cognitive deficits (Audrain-McGovern et al. 2004; Reynolds 2006).
