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Effects of Marijuana Use on Prefrontal and Parietal Volumes and Cognition in Emerging Adults

Price, Jenessa S
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1399624029

Abstract Details

2014, PhD, University of Cincinnati, Arts and Sciences: Psychology.
Introduction: Initiation of marijuana (MJ) use typically coincides with continuing brain neuromaturation, particularly in frontal and parietal areas. Chronic MJ use has been associated with disruption of frontoparietal pathways and dose-dependent deficits in attention and executive function among young users. Imaging studies reveal evidence of white matter microstructural abnormalities and indications of disruption of pruning processes among MJ-using adolescents. This study investigated past year MJ use and its interaction with gender on prefrontal cortex (PFC) and parietal cortex volumes and executive function in a sample of healthy emerging adults. Method: Participants were 27 MJ users (>25 past year MJ joints) and 32 controls (<5 past year and <50 lifetime MJ joints), balanced for gender, and meeting eligibility requirements (ages 18-25 and no history of medical/neurologic illness, DSM-IV Axis I diagnosis, or heavy other drug use). Urine toxicology testing assessed abstinence. Self-report measures included the Frontal Systems Behavior Scale (FRSBE) and the BIS/BAS. Cognitive variables included tasks measuring complex attention and cognitive inhibition. FreeSurfer pre-processed and obtained PFC and parietal cortex volumes on T-1 weighted 3D anatomical brain images, and the author performed blind inspection and editing when necessary. A series of multiple regressions examined whether MJ use status predicted PFC and parietal volumes after controlling for ICV, body mass index, verbal IQ, gender, alcohol, hallucinogen and nicotine use; a second block examined the interaction between MJ use and gender. A second series of regressions examined impact of past year MJ use on PFC and parietal volumes utilizing the same covariates. Post-hoc analyses consisted of brain-behavior correlations between ROI findings and cognitive variables. Fisher’s z tests assessed whether brain-behavior relationships differed between MJ users and controls. Results: On self-report measures, past year MJ users endorsed significantly more symptoms of executive dysfunction and disinhibition versus controls on the FRSBE. After controlling for gender, BMI, verbal IQ estimate, and alcohol, nicotine and hallucinogen use, MJ users demonstrated significantly smaller medial orbitofrontal cortex (mOFC; p=.004; f2=.18) and inferior parietal volumes (p=.04; f2=.09); increased past year MJ use dose-dependently predicted smaller mOFC volume (p=.05; f2=.09). There were no significant group-by-gender interactions. Post-hoc analyses yielded a significant brain-behavior difference by group; smaller mOFC volumes were associated with poorer WAIS-III Letter Number Sequencing, with the opposite pattern seen in controls (z=1.87, p<.05). Overall, smaller mOFC volumes were associated with poorer complex attention and inhibitory processing among MJ users. Discussion: Among emerging adult men and women, MJ users demonstrated significantly smaller mOFC and inferior parietal volumes compared to controls, and smaller mOFC volumes were dose-dependently associated with past year MJ use. In MJ users, smaller volumes were associated with poorer complex attention and inhibitory processing. Regional findings suggest ongoing disruption to normal neurodevelopmental processes associated with regular MJ use. Group differences in the inferior parietal region may reflect premorbid factors that differ among youth who initiate use. Future research should incorporate multi-modal imaging, genotyping, and longitudinal design in examining the neurocognitive effects of MJ use, towards the goal of characterizing at-risk populations and creating optimal interventions.
Paula Shear, Ph.D. (Committee Chair)
Jeffery Epstein, Ph.D. (Committee Member)
Krista Medina, Ph.D. (Committee Member)
62 p.
Clinical Psychology
marijuana; cognition; prefrontal cortex; parietal cortex; emerging adult

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Citations

  • Price, J. S. (2014). Effects of Marijuana Use on Prefrontal and Parietal Volumes and Cognition in Emerging Adults [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1399624029

    APA Style (7th edition)

  • Price, Jenessa. Effects of Marijuana Use on Prefrontal and Parietal Volumes and Cognition in Emerging Adults. 2014. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1399624029.

    MLA Style (8th edition)

  • Price, Jenessa. "Effects of Marijuana Use on Prefrontal and Parietal Volumes and Cognition in Emerging Adults." Doctoral dissertation, University of Cincinnati, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1399624029

    Chicago Manual of Style (17th edition)

ucin1399624029
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This open access ETD is published by University of Cincinnati and OhioLINK.