Methadone Maintenance Treatment and Cognitive Function: A Systematic Review
Grace Y. Wang, Trecia A. Wouldes and Bruce R. Russell
Affiliation: School of Pharmacy, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
Methadone has been used as a pharmacotherapy for the treatment of opiate dependence since the mid-1960s.
Many studies examining the benefits of methadone maintenance treatment (MMT) for opiate dependence have
documented a significant reduction in both criminal behavior and the use of other opiates. Nevertheless, emerging
evidence suggests that MMT may impair cognitive function. However, it is unclear as to the part methadone dose,
duration of MMT or plasma level may play in any observed deficits. Given the large number of people enrolled in MMT
world-wide and the potential for deficits in cognitive function, a systematic review of the research investigating the
association between MMT and cognitive function seemed warranted. The following databases were searched with a
combination of free-text and thesaurus terms (methadone AND cognition): MEDLINE In-Process, EMBASE, PsycINFO
and EBM Reviews-Cochrane Central Register of Controlled Trials. Seventy-eight articles were retrieved of which 35 met
the inclusion criteria. The majority of research suggests that MMT is associated with impaired cognitive function and that
deficits extended across a range of domains. However, caution is required when interpreting these results due to the
methodological limitations associated with many studies. Further research that includes a combination of psychological
and physiological measures within well-controlled group comparison studies is required to more accurately assess which
cognitive domains are affected.
Keywords: Cognition, methadone maintenance, neuropsychological test, opiate dependence, systematic review.
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