HighlightsA broad range of domains of neuropsychological performance are significantly impaired in studies which have compared  methadone population s with the healthy controls .
However low power , poor quality and heterogenous population s limit the interpretation of these results .Short term ( less than 1 year ) abstinent groups , when compared with methadone groups , still exhibited cognitive impairments but results are inconclusive .
It is still not clear what the role of global sedative effects of opioids such as methadone have on cognitive impairment .
Only higher quality longitudinal studies using ecologically valid cognitive tests , in well‐defined population groups can address this question .Methadone population s present with a broad range of neuropsychological impairment when compared with healthy controls .
Results : Data from a total cohort of 1063 CM , 412 AP and 879 HP participants , from 23 independent studies  indicate global impairments in neurocognitive function in CM relative to HP participants .
Conclusion : Method ological issues such as small sample sizes , heterogeneity and poor quality limited the interpretation of the results and does not address whether the observed impairments reflect co‐morbid functioning , methadone‐related sedation and /or other factors .
Introduction : There is a presumption that neurocognition is commonly impaired in chronic methadone exposed individuals ( CM ) when compared with healthy controls ( HP ) .
Additionally , it remains unclear if short term ( < 1 year ) abstinence ( AP ) is associated with an altered cognitive profile when compared with CM .
Punishment Induces Risky Decision-Making in Methadone-Maintained Opiate Users but not in Heroin Users or Healthy Volunteers
Reinforcing properties of psychoactive substances are considered to be critically involved in the development and maintenance of substance dependence . While accumulating evidence suggests that the sensitivity to reinforcement values may generally be altered in chronic substance users , relatively little is known about the influence reinforcing feedback exerts on ongoing decision-making in these individuals . Decision-making was investigated using the Cambridge Risk Task , in which there is a conflict between an unlikely large reward option and a likely small reward option . Responses on a given trial were analyzed with respect to the outcome on the previous trial , providing a measure of the impact of prior feedback in modulating behavior . Five different groups were compared : ( i ) chronic amphetamine users , ( ii ) chronic opiate users in methadone maintenance treatment ( MMT ) , ( iii ) chronic users of illicit heroin , ( iv ) ex-drug users who had been long-term amphetamine / opiate users but were abstinent from all drugs of abuse for at least 1 year and ( v ) matched controls without a history of illicit substance use . Contrary to our predictions , choice preference was modified in response to feedback only in opiate users enrolled in MMT . Following a loss , the MMT opiate group chose the likely small reward option significantly less frequently than controls and heroin users . Our results suggest that different opiates are associated with distinctive behavioral responses to feedback . These findings are discussed with respect to the different mechanisms of action of heroin and methadone
HighlightsA broad range of domains of neuropsychological performance are significantly impaired in studies which have compared  methadone population s with the healthy controls .
However low power , poor quality and heterogenous population s limit the interpretation of these results .Short term ( less than 1 year ) abstinent groups , when compared with methadone groups , still exhibited cognitive impairments but results are inconclusive .
It is still not clear what the role of global sedative effects of opioids such as methadone have on cognitive impairment .
Only higher quality longitudinal studies using ecologically valid cognitive tests , in well‐defined population groups can address this question .Methadone population s present with a broad range of neuropsychological impairment when compared with healthy controls .
Results : Data from a total cohort of 1063 CM , 412 AP and 879 HP participants , from 23 independent studies  indicate global impairments in neurocognitive function in CM relative to HP participants .
Conclusion : Method ological issues such as small sample sizes , heterogeneity and poor quality limited the interpretation of the results and does not address whether the observed impairments reflect co‐morbid functioning , methadone‐related sedation and /or other factors .
Introduction : There is a presumption that neurocognition is commonly impaired in chronic methadone exposed individuals ( CM ) when compared with healthy controls ( HP ) .
Additionally , it remains unclear if short term ( < 1 year ) abstinence ( AP ) is associated with an altered cognitive profile when compared with CM .