title: Combined effects of marijuana and nicotine on memory performance and hippocampal volume.
abstract: Combined use of marijuana (MJ) and tobacco is highly prevalent in today's population. Individual use of either substance is linked to structural brain changes and altered cognitive function, especially with consistent reports of hippocampal volume deficits and poorer memory performance. However, the combined effects of MJ and tobacco on hippocampal structure and on learning and memory processes remain unknown. In this study, we examined both the individual and combined effects of MJ and tobacco on hippocampal volumes and memory performance in four groups of adults taken from two larger studies: MJ-only users (n=36), nicotine-only (Nic-only, n=19), combined marijuana and nicotine users (MJ+Nic, n=19) and non-using healthy controls (n=16). Total bilateral hippocampal volumes and memory performance (WMS-III logical memory) were compared across groups controlling for total brain size and recent alcohol use. Results found MJ and MJ+Nic groups had smaller total hippocampal volumes compared to Nic-only and controls. No significant difference between groups was found between immediate and delayed story recall. However, the controls showed a trend for larger hippocampal volumes being associated with better memory scores, while MJ+Nic users showed a unique inversion, whereby smaller hippocampal volume was associated with better memory. Overall, results suggest abnormalities in the brain-behavior relationships underlying memory processes with combined use of marijuana and nicotine use. Further research will need to address these complex interactions between MJ and nicotine.
authors.affiliation: The Center for BrainHealth, School of Behavioral and Brain Sciences, University of Texas at Dallas, United States. Electronic address: Francesca.Filbey@utdallas.edu.
authors.forename: Francesca M
authors.initials: FM
authors.lastname: Filbey
authors.affiliation: The Center for BrainHealth, School of Behavioral and Brain Sciences, University of Texas at Dallas, United States.
authors.forename: Tim
authors.initials: T
authors.lastname: McQueeny
authors.affiliation: The Center for BrainHealth, School of Behavioral and Brain Sciences, University of Texas at Dallas, United States.
authors.forename: Shrinath
authors.initials: S
authors.lastname: Kadamangudi
authors.affiliation: The Center for BrainHealth, School of Behavioral and Brain Sciences, University of Texas at Dallas, United States.
authors.forename: Collette
authors.initials: C
authors.lastname: Bice
authors.affiliation: The Center for BrainHealth, School of Behavioral and Brain Sciences, University of Texas at Dallas, United States.
authors.forename: Ariel
authors.initials: A
authors.lastname: Ketcherside
mesh_terms: D000293:Adolescent; D000328:Adult; D002188:Cannabis / Q000009:adverse effects; D003071:Cognition / Q000187:drug effects / Q000502:physiology; D004338:Drug Combinations; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000473:pathology*; D006801:Humans; D007858:Learning / Q000187:drug effects / Q000502:physiology; D008297:Male; D008385:Marijuana Smoking / Q000473:pathology*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D009538:Nicotine / Q000494:pharmacology; D012907:Smoking / Q000473:pathology*; D055815:Young Adult
chemical_list: D004338:Drug Combinations; D009538:Nicotine
keywords: Cannabis; Comorbid substance use; Hippocampus; Morphometry; Nicotine