Impaired inhibitory control of behavior in chronic cocaine users

This study examined the ability to inhibit and execute behavioral responses in adult cocaine users and in an aged-matched sample with no history of cocaine use. Subjects (n=22) were identified as cocaine users by testing positive for the presence of cocaine or benzoylecgonine in urine-analysis and by self-reported cocaine use. Control subjects (n=22) tested negative in urine-analysis and reported no past cocaine use. Response inhibition and response execution were measured by a stop-signal paradigm using a choice reaction time task that engaged subjects in responding to go-signals when stop-signals occasionally informed them to inhibit the response. Cocaine users displayed significantly poorer ability to inhibit their behavioral responses than did controls. Specifically, cocaine users required more time to inhibit responses to stop-signals and displayed a lower probability of inhibiting their responses. Cocaine users did not differ from controls in their ability to execute responses as measured by their speed and accuracy of responses to go-signals. These findings are important because they identify a specific deficit involving behavioral inhibition that could contribute to cocaine abuse, and explain its association with other disorders of self-regulation, such as ADHD.