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 .
Assessment of study quality for systematic reviews: a comparison of the Cochrane Collaboration Risk of Bias Tool and the Effective Public Health Practice Project Quality Assessment Tool: methodological research.
BACKGROUND The Cochrane Collaboration is strongly encouraging the use of a newly developed tool , the Cochrane Collaboration Risk of Bias Tool ( CCRBT ) , for all review groups . However , the psychometric properties of this tool to date have yet to be described . Thus , the objective of this study was to add information about psychometric properties of the CCRBT including inter-rater reliability and concurrent validity , in comparison with the Effective Public Health Practice Project Quality Assessment Tool ( EPHPP ) . METHODS Both tools were used to assess the method ological quality of 20 r and omized controlled trials included in our systematic review of the effectiveness of knowledge translation interventions  to improve the management of cancer pain . Each study assessment was completed independently by two review ers using each tool . We analysed the inter-rater reliability of each tool 's individual domains , as well as final grade assigned to each study . RESULTS The EPHPP had fair inter-rater agreement for individual domains and excellent agreement for the final grade . In contrast , the CCRBT had slight inter-rater agreement for individual domains and fair inter-rater agreement for final grade . Of interest , no agreement between the two tools was evident in their final grade assigned to each study . Although both tools were developed to assess ' quality of the evidence ' , they appear to measure different constructs . CONCLUSIONS Both tools performed quite differently when evaluating the risk of bias or method ological quality of studies in knowledge translation interventions for cancer pain . The newly introduced CCRBT assigned these studies a higher risk of bias . Its psychometric properties need to be more thoroughly vali date d , in a range of research fields , to underst and fully how to interpret results from its application
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 .