This research attempts to answer this question “Is there any difference between methadone users, non- methadone addicts and normal people in terms of cognitive abilities and prospective memory? In this research, an ex-post facto study was used to compare the cognitive abilities and prospective memory in methadone addicts, non-methadone addicts and ordinary people. The study population consisted of all rehabilitated addicts (methadone and non-methadone) in Chenaran Prison in 2015, out of whom 56 people (28 methadone and 28 non-methadone addicts) were selected. Also, for the sake of comparison, 20 normal subjects were selected and the cognitive abilities questionnaire and prospective memory questionnaire were given to samples. In the finding there are two parts that used ANOVA for analysis data. In the part one, the results showed that there is no significant comparison between prospective memory in three groups. In the part two, the results showed that memory, inhibitory control, planning, sustained attention, cognitive abilities, social cognition and total score of cognitive abilities in three groups were significantly different (P <0.05). Our research indicates a relative improvement in cognitive abilities. We posit that rehabilitation can elevate the prospective memory of rehabilitated methadone and non- methadone addicts to the level of ordinary people. Also with respect to cognitive abilities, the rehabilitation can improve the cognitive abilities of rehabilitated methadone addicts.

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