Cognitive impairment among methadone maintenance patients

Aims. To compare the cognitive performance of methadone maintenance patient s (MMPs) and a matched sample of non-heroin-using control subjects, and to ascertain risk factors for poorer cognitive performance. Design. Matched co ntrol study. Setting. Sydney, Australia. Participants. Thirty MMPs and 30 n on-heroin using controls, matched for age, gender and education. Findings. The MMP group had significantly higher rates than controls of alcohol depen dence, heroin overdose and head injury. There was no difference between the groups on pre-morbid functioning. The MMP group performed significantly po orer than controls on all of the neuropsychological domains measured: infor mation processing, attention, short-term visual memory, delayed visual memo ry, short-term verbal memory, long-term verbal memory and problem solving. A life-time diagnosis of alcohol dependence and the number of non-fatal her oin overdoses were independent significant predictors of poorer cognitive p erformance. Conclusions. In addition to high rates of psychiatric morbidity , MMPs also show cognitive deficits compared to matched controls. A history of alcohol dependence and repeated exposure to overdose increase the likel ihood of cognitive impairment. The current study does not rule out the poss ibility of other factors, that were not measured, that may contribute to co gnitive impairment among this MMPs.