Hate to do this in a rush because I'm hustling to make it to an appointment on time, but appears the answer may not be as clear cut as we would like. For a study of what may be an extreme case, previously heavy heroin addicts, see, Prosser J, Cohen LJ, Steinfeld M et al, Neuropsychological functioning in opiate-dependent subjects receiving and following methadone maintenance treatment, Drug Alcohol Depend. 2006 Oct 1;84(3):240-7. Epub 2006 Mar 20, FREE FULL TEXT AT http://www.ncbi.nlm.nih.gov/pmc/arti...nihms30979.pdf

Department of Psychiatry and Behavioral Sciences, Beth Israel Medical Center, Albert Einstein College of Medicine, New York, NY 10003, USA. jprosser@chpnet.org

Abstract
OBJECTIVE: An accumulating body of research suggests that former heroin abusers in methadone maintenance therapy (MMT) exhibit deficits in cognitive function. Whether these deficits are present in former methadone maintained patients following discontinuation of MMT is unknown. This study tests the hypothesis that former heroin users who have detoxified from methadone maintenance therapy and are drug-free have less pronounced cognitive impairment than patients continuing long-term MMT.

METHOD: A series of neuropsychological tests were administered to three groups of subjects: 29 former heroin addicts receiving methadone maintenance treatment, 27 former heroin addicts withdrawn from all opiates, and 29 healthy controls without a history of drug dependence. Testing included Wechsler Adult Intelligence Scale-Revised Vocabulary Test, the Stroop Color-Word Test, the Controlled Oral Word Association Test, the Benton Visual Retention Test, and a Substance Use Inventory.

FINDINGS: Both methadone-maintained and abstinent subject groups performed worse than controls on tasks that measured verbal function, visual-spatial analysis and memory, and resistance to distractibility. Abstinent subjects performed worse than their methadone maintained counterparts on tests measuring visual memory and construct formation. Cognitive impairment did not correlate with any index of drug use.

CONCLUSIONS: We confirmed previous findings of neuropsychological impairment in long-term MMT recipients. Both patients receiving MMT and former heroin users in prolonged abstinence exhibited a similar degree of cognitive impairment. Cognitive dysfunction in patients receiving methadone maintenance may not resolve following methadone detoxification.

PMID: 16545923 [PubMed - indexed for MEDLINE]