Verbal working memory deficits in abstinent heroin abusers

A prevailing belief is that opioids tend not to impair cognitive performance in opioid-dependent users. However, the impact of heroin abuse on verbal memory, especially on working memory, is not well studied and the results available are inconsistent.

This study was carried out to test the hypothesis that abstinent heroin abusers have intact working memory capacity.

N-back task and backward digit span task were used to measure the verbal working memory capacity in 28 abstinent heroin abusers and 25 controls matched for age, education level and gender. Forward digit span task was used as a control task to measure short-term memory capacity.

Compared with the control subjects, heroin abusers showed normal backward/forward digit spans but significant performance impairment in the n-back task.

Abstinent heroin abusers have intact short-term memory capacity but impaired verbal working memory capacity.