Age of onset of marijuana use impacts inhibitory processing

Difficulties in the ability to successfully inhibit impulsive behaviors have been reported in marijuana (MJ) smokers, yet few studies have made direct comparisons between early (prior to age 16) and late (age 16 or later) onset MJ smokers, specifically during behavioral inhibition tasks. The current study utilized the Multi-Source Interference Task (MSIT) during functional magnetic resonance imaging (fMRI) in chronic, heavy MJ smokers and healthy non-MJ smoking controls which revealed a more focal pattern of anterior cingulate activity in controls relative to smokers. Early onset smokers had more focal activation but tended to make more errors of commission relative to late onset smokers, suggesting a possible neural adaptation despite difficulty with behavioral inhibition. Further investigation is warranted, as early exposure to MJ may result in reorganization of critical brain regions.

► Despite similar MSIT performance, MJ users had significantly different activation than controls.
► During the MSIT, MJ smokers had greater activation within cingulate cortex than controls.
► Early onset smokers had more focal activation but made more errors relative to later onset smokers.
► Findings may suggest neural compensation in early onset MJ smokers despite inhibitory difficulty.