Abstract
Fifty-four methadone-maintained patients and 54 healthy controls, matched for age, gender and educational attainment, completed a battery of six cognitive-psychomotor performance tests. Results of previous studies were replicated in four areas. An attention task was performed less well by patients [mean difference more than 0.7 standard deviations (SD)] as was a tachistoscopic perception task (0.3 SD). On a simple-choice reaction test, patients showed higher speed in decision making and motor reaction as well as an increased number of decision errors (0.3 SD each). Performing a tracking test, patients showed less deviations (0.4 SD) combined with more time needed (0.8 SD). Our data go beyond previous (seemingly inconsistent) research findings by showing that patients did less well by more than 0.6 SD when on higher speed levels. Absolving a test on visual structuring, more patients than controls achieved a 100% accuracy level (52 vs. 30%), but at the same time patients were slower (0.6 SD) than controls. An inferior test performance of patients in methadone maintenance treatment has been confirmed in some areas, especially in attention. However, the fairly moderate size of these effects and the fact that in the majority of measures the observed variance was better explained by sociodemographic features than by group membership lead on the conclusion that belonging to the group of methadone patients alone is not necessarily sufficient to predict an impairment in cognitive-psychomotor skills. To conclude, assessment of fitness for certain tasks or occupations should be done individually for each patient and should take into account comorbidity, including the extent of alcohol and other drug use.