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Cogn Affect Behav Neurosci. 2019 Feb 26. doi: 10.3758/s13415-019-00704-4. [Epub ahead of print]

Marijuana use and major depressive disorder are additively associated with reduced verbal learning and altered cortical thickness.

Author information

1
Department of Psychiatry, University of Illinois at Chicago, Chicago, IL, USA.
2
Department of Psychiatry, Massachusetts General Hospital (MGH) Center for Addiction Medicine, 101 Merrimac Street, Suite 320, Boston, MA, 02114, USA.
3
Harvard Medical School, Boston, MA, USA.
4
Department of Psychiatry, Massachusetts General Hospital (MGH) Center for Addiction Medicine, 101 Merrimac Street, Suite 320, Boston, MA, 02114, USA. jgilman1@partners.org.
5
Harvard Medical School, Boston, MA, USA. jgilman1@partners.org.
6
Department of Radiology, MGH, Athinoula A. Martinos Center in Biomedical Imaging, Charlestown, MA, USA. jgilman1@partners.org.

Abstract

Marijuana (MJ) use and major depressive disorder (MDD) have both been associated with deficits in verbal learning and memory as well as structural brain abnormalities. It is not known if MJ use by those with MDD confers additional impairment. The goal of this study was to examine unique and combined effects of MDD and MJ use on verbal memory and brain structure. Young adults (n=141) aged 18-25 years with MJ use and no lifetime MDD (MJ, n=46), MDD and no MJ use (MDD, n=23), MJ use and lifetime MDD (MDD+MJ, n=24), and healthy controls without MDD or MJ use (CON, n=48) were enrolled. Participants completed the California Verbal Learning Test, Second Edition (CVLT-II), a measure of verbal learning and memory. A sub-sample of 82 participants also underwent a structural magnetic resonance imaging (MRI) scan. Group differences in CVLT-II performance, cortical thickness, and hippocampal volume were assessed. We found an additive effect of MDD and MJ on memory recall. Only MDD, but not MJ, was associated with poorer initial learning, fewer words recalled, more intrusion errors, and lower percent retention. There was also an additive effect of MDD and MJ use on reduced cortical thickness in the middle temporal gyrus. Findings indicate that MJ use and MDD have additive adverse associations with verbal recall and cortical thickness in the middle temporal gyrus, suggesting that MJ use among those with MDD may be contraindicated. Prospective studies are warranted to determine whether this association may be causal.

KEYWORDS:

CVLT-II; Cannabis; Cortical thickness; MDD; MRI; Major depressive disorder; Marijuana; Verbal memory

PMID:
30809764
DOI:
10.3758/s13415-019-00704-4

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