Opioid abuse and cognitive performance.

A few recent studies provide evidence for performance impairment in dependent opioid abusers enrolled in methadone maintenance programs. However, it is difficult to differentiate the effects of a history of long-term opioid (or polydrug) abuse from the effects of methadone maintenance itself. The purpose of the present study was to address this issue by comparing the performance of a newly recruited group of 20 currently abstinent former opioid abusers retrospectively to two groups (18 methadone maintenance patients (MMP); 21 matched non-drug abusing controls) reported on previously in our laboratory [Mintzer, M.Z., Stitzer, M.L., 2002. Cognitive impairment in methadone maintenance patients. Drug Alcohol Depend. 67, 41-51], using the same performance testing battery. The abstinent abusers were demographically similar to the MMP and matched controls, and reported histories of drug use similar to those of the MMP. Although conclusions are somewhat limited by the small sample size, performance of the abstinent abusers fell between that of the MMP and controls on many measures, suggesting that methadone maintenance may be associated with additional impairment over and above that associated with long-term abuse, and that recovery of functioning may occur during abstinence. Further research is necessary to explore the factors underlying performance impairment in MMP and to determine the clinical significance of the observed impairments for daily performance in the natural environment.