[Effects of methadone maintenance treatment on working memory in male heroin dependent patients]

To explore the differences of working memory task performance between male patients with heroin dependence in methadone maintenance treatment (MMT) and healthy controls (HC).

A total of 42 heroin-dependent patients at Huainan City Psychiatric Hospital from May 2011 to October 2011 were compared with 31 gender- and age-matched HCs on such working memory tests as visual-space, visual-verbal and visual-face. Then the accurate rate and reaction time of the above tasks were between two groups.

The participants with anxiety or depression were excluded. All MMT subjects were required to have negative urine toxicology screening tests. The accurate rate of verbal working memory of the patients was worse than that of HCs (83% ± 9% vs 89% ± 10%). And the difference was significant between two groups (t(71) = -2.631, P = 0.010). The accurate rate of visual-object and visual-spatial working memory showed no significant differences between two groups (P > 0.05). The differences in reaction time on these tasks showed no statistical significance between two groups (P > 0.05). In addition, the dose of methadone and the duration of MMT revealed no significant effects on the performance of working memory and executive functions.

The disproportion impairment of patients on space, verbal and face working memory is probably due to the differential heroin-mediated injuries of encephalic regions. Methadone has no effect on working memory and executive functions in the patients with a history of heroin use during maintenance treatment intervention.