Waiting to respond also appears to be impaired in substance use disorders, whether one uses 5CSRTT variants81 or DRL tests.82 These deficits may well proceed the onset of drug use because the 5CSRTT can be used to identify a pattern of waiting impulsivity – present in a minority of rats – that predicts an elevated propensity to self-administer cocaine or nicotine,83, 84 but not heroin83, 85 and with enhanced susceptibility for the development of a compulsive pattern of cocaine seeking.85 Finally, impulsive responding in the 5CSRTT predicts escalation of sucrose intake and susceptibility to cue-induced reinstatement of sucrose seeking, pointing to its ability to predict a dyscontrolled, hyperactive reward-seeking and –taking phenotype that extends beyond drugs of abuse.86 By contrast, neither amphetamine87 or heroin or cocaine self-administration,88 even when coupled with repeated withdrawal episodes, produces lasting changes in premature responding in the 5CSRTT at the group level in rats; strikingly, when analyses are focused only on rats with pre-existing high impulsivity in the 5CSRTT, cocaine self-administration experience actually lessens waiting impulsivity.89
