Comparison of cognitive performance in methadone maintenance patients with and without current cocaine dependence

Background: There is evidence for psychomotor and cognitive performance impairment in methadone maintenance patients (MMP), as well as in individuals with current cocaine dependence. It is unknown whether MMP with concurrent cocaine dependence perform worse on tests of cognitive function than MMP without cocaine dependence. Methods: Performance was compared between MMP with and without current cocaine dependence (MMP/CD+; N=53 and MMP/CD-; N=24) on a standard battery of tasks designed to measure psychomotor performance, attention, episodic and working memory, and executive function. Results: Participant characteristics were mostly similar across groups. However, the MMP/CD+ group had a shorter duration of methadone treatment, and a larger percentage of participants with self-reported 30-day poly-substance abuse and positive urine drug tests on the day of cognitive testing. There were no differences between the groups on measures of balance, psychomotor coordination, divided attention, working memory, most measures of episodic memory, or executive function. Relative to MMP/CD-, MMP/CD+ showed significant impairment on select measures of psychomotor performance/attention (simple reaction time and trail-making test A) and episodic memory (higher false alarm rates on recognition memory). Conclusions: The absence of differences between MMP/CD+ and MMP/CD- on measures of higher order cognitive functions, and the relatively small magnitude between-group differences on other measures suggest that current cocaine dependence, in the absence of cocaine intoxication, is unlikely to be associated with clinically meaningful increases in performance impairment in MMP.