Effects of marijuana use on prefrontal and parietal volumes and cognition in emerging adults.
BACKGROUND
Chronic marijuana (MJ) use among adolescents has been associated with structural and functional abnormalities, particularly in developing regions responsible for higher order cognition.


OBJECTIVE
This study investigated prefrontal (PFC) and parietal volumes and executive function in emerging adult MJ users and explored potential gender differences.


METHODS
Participants (ages 18-25) were 27 MJ users and 32 controls without neurologic or psychiatric disorders or heavy other drug use. A series of multiple regressions examined whether group status, past year MJ use, and their interactions with gender predicted ROI volumes. Post hoc analyses consisted of brain-behavior correlations between volumes and cognitive variables and Fisher's z tests to assess group differences.


RESULTS
MJ users demonstrated significantly smaller medial orbitofrontal (mOFC; p = 0.004, FDR p = 0.024) and inferior parietal volumes (p = 0.04, FDR p = 0.12); follow-up regressions found that increased past year MJ use did not significantly dose-dependently predict smaller mOFC volume in a sub-sample of individuals with at least one past year MJ use. There were no significant gender interactions. There was a significant brain-behavior difference by group, such that smaller mOFC volumes were associated with poorer complex attention for MJ users (p < 0.05).


CONCLUSIONS
Smaller mOFC volumes among MJ users suggest disruption of typical neurodevelopmental processes associated with regular MJ use for both genders. These results highlight the need for longitudinal, multi-modal imaging studies providing clearer information on timing of neurodevelopmental processes and neurocognitive impacts of youth MJ initiation.
Department of Psychiatry, Harvard Medical School-McLean Hospital, Belmont, MA, USA.
Jenessa S
JS
Price
Tim
T
McQueeny
Skyler
S
Shollenbarger
Erin L
EL
Browning
Jon
J
Wieser
Krista M
KM
Lisdahl
D000293:Adolescent; D000328:Adult; D002188:Cannabis; D003071:Cognition / Q000187:drug effects*; D056344:Executive Function / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000473:pathology* / Q000503:physiopathology / Q000523:psychology; D008385:Marijuana Smoking / Q000473:pathology* / Q000523:psychology; D009929:Organ Size / Q000187:drug effects; D010296:Parietal Lobe / Q000187:drug effects* / Q000473:pathology; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000473:pathology; D012727:Sex Characteristics; D055815:Young Adult