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© 2012 John Wiley & Sons A/S

Acta Neuropsychiatrica 2012
All rights reserved
DOI: 10.1111/j.1601-5215.2012.00679.x

ACTA NEUROPSYCHIATRICA

Working memory subsystems are impaired in
chronic drug dependents
Soliman AM, Gadelrab HF, Elfar RM. Working memory subsystems are impaired in chronic drug dependents.
Background: A large body of research that has investigated substance dependence and working memory (WM) resources, yet no prior study has used a comprehensive test battery to examine the impact of chronic drug dependence on WM as a multi-component system.

Objectives: This study examined the efficiency of several WM components in participants who were chronic drug dependents. In addition, the functioning of the four WM components was compared among dependents of various types of drugs.

Method: In total, 128 chronic drug dependents participated in this study. Their average age was 38.48 years, and they were classified into four drug-dependence groups. Chronic drug dependents were compared with a 36-participant control group that had a mean age of 37.6 years. A WM test battery that comprised eight tests and that assessed each of four WM components was administered to each participant.

Results: Compared with the control group, all four groups of drug dependents had significantly poorer test performance on all of the WM tasks. Among the four groups of drug users, the polydrug group had the poorest performance scores on each of the eight tasks, and the performance scores of the marijuana group were the least affected. Finally, the forward digit span task and the logical memory tasks were less sensitive than other tasks when differentiating between marijuana users and the normal participants.

Conclusion: The four components of WM are impaired among chronic drug dependents. These results have implications for the development of tools, classification methods and therapeutic strategies for drug dependents.

Abdrabo Moghazy Soliman1,4 ,
Hesham Fathy Gadelrab2,4 ,
Rania Mohamed Elfar3,4
1

Department of Psychology, Tanta University, Egypt;
Department of Educational Psychology, Mansoura
University, Egypt; 3 Department of Psychology, Kafr
Elshiekh University, Egypt; and 4 Department of
Psychology, Umm Al-Qura University, Makkah,
Saudi Arabia
2

Keywords: drug dependence; verbal; visuospatial
working memory; working memory
Dr. Abdrabo Moghazy Soliman, Department of
Psychology, Umm Al-qura University, Makkah,
Saudi Arabia.
Tel/Fax: +9665281719;
E-mail: dr.asoliman@yahoo.co.uk
Accepted for publication June 20, 2012

Significant outcomes





Compared with drug-free participants, drug dependents had functional impairments in all of the working memory (WM) components that we tested.
Among the groups of drug dependents that we studied (heroin, cocaine, marijuana and polydrug users), polydrug dependents had the most severe performance impairments in tests of the four WM components that we studied compared with the test results of drug-free participants. The type of drug dependence in which an individual engages has a differential and negative impact on the functioning of WM components.

1

Soliman et al.
Limitations




Causality cannot be inferred from our cross-sectional data. Thus, we cannot conclude that drug dependence causes the impairment of WM.
The findings of this study are limited to chronic drug dependents who used certain types of drugs for prolonged periods of time.
Interpretation of the non-significant differences between the marijuana users and the drug-free participants in our study that were observed in tests of specific WM components should be made with caution.

Introduction

WM plays a key role in the service of performing
complex cognitive tasks by means of maintaining and
processing various types of information (i.e. verbal
and visuospatial). Previous research has suggested
that WM is positively correlated with a large number
of cognitive processes,...
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