Working Memory Impairment in Cannabis- and Opioid-Dependent Adolescents

Abstract

ABSTRACT. Background: Cannabis and opioid use are associated with cognitive impairment, whether preexisting or substance-induced, but there have been few substance-specific assessments of cognitive functioning in adolescent substance users. Working memory impairment may be particularly important, as it has been linked to poorer performance in substance abuse treatment. Methods: Working memory (Wechsler Intelligence Scale for Children-IV or Adult Intelligence Scale-IV) and baseline substance use were assessed in 42 youth (mean age = 17.9 years, SD = 1.3, range: 16–20; 65% Caucasian, 30% female) 1–2 weeks after admission to residential treatment with supervised abstinence, 19 for primary cannabis dependence and 23 for primary opioid dependence. Results: There were substantial deficits in working memory in both groups, with significant differences (P < .001) between the opioid (M = 39.1th%ile, SD = 25.6) and cannabis (M = 16.3th%ile, SD = 13.6) groups. The primary opioid group had high rates of cannabis use, with no significant difference in past-month days of cannabis use from the primary cannabis group. The opioid group was older and had completed more years of formal education. Seventy-nine percent of the cannabis group had public health care coverage (mostly Medicaid), compared with 24% of the opioid sample. Conclusions: Working memory impairment was substantial in treatment-seeking youth with primary cannabis and opioid dependence (the latter actually having comparable rates of cannabis use), and significantly more pronounced in the primary cannabis-dependent group. Without an assessment of working memory prior to substance exposure, the differential contributions of substance-induced vs. preexisting impairment are unclear. Lower scores in the cannabis group may reflect lower socioeconomic status (SES), which is typically correlated with cognitive performance. These findings highlight underrecognized cognitive impairment in youth with SUDs, especially inner-city cannabis-dependent youth. Modification of treatments to account for cognitive capacity and/or cognitive remediation interventions may be indicated to improve treatment outcomes.

Keywords:

• Adolescents, cannabis, opioid, working memory, substance use

ACKNOWLEDGMENTS

Dr. Miriam Mintzer is presently at Center for Scientific Review, National Institutes of Health, Bethesda, MD, USA. The research reported in this article was conducted while Dr. Mintzer was employed at Johns Hopkins University. The opinions expressed in this article are the authors' own and do not reflect the views of the National Institutes of Health, the Department of Health and Human Services, or the United States government. The research reported in this article was conducted while Dr. Schacht was employed at Johns Hopkins University. The opinions expressed in this article are the authors’ own and do not reflect the view of the University of Maryland–Baltimore County. Dr. Marc Fishman is the Medical Director of Mountain Manor Treatment Center (MMTC) where patients are enrolled in this study. Dr. Fishman is a part-time faculty member of the Johns Hopkins University. He is a beneficiary of the trust that owns MMTC. Dr. Fishman also serves on the governing board of the trust and the Board of Directors of MMTC. This arrangement has been reviewed and approved by the Johns Hopkins University in accordance with its conflict of interest policies.

FUNDING

The current project was supported by funds from Mountain Manor Treatment Center and Johns Hopkins School of Medicine Bayview, Department of Psychiatry and Behavioral Sciences.

AUTHOR CONTRIBUTIONS

Drs. Vo and Schacht contributed to data collection, analysis, and interpretation and drafting and revision of the current paper. Drs. Mintzer and Fishman contributed to the research concept and design, data interpretation, and drafting and revising process of this paper.