All participants gave their written, informed consent before participating in this study. Participants were 40 daily marijuana smokers (ten females, mean age=20.2) recruited from the Boulder, Colorado area. Thirty-five participants identified as Caucasian (of whom six identified as Hispanic), one as Black, three as Asian, and one as Native American. Individuals were excluded if they were younger than 18 or older than 25, taking psychotropic medication, currently using any substance other than marijuana, attempting to stop smoking marijuana, or currently in substance abuse treatment. Individuals who met DSM-IV diagnostic criteria for other SUD (e.g., alcohol dependence) were excluded, as were individuals who reported any conditions that might interfere with smoked marijuana administration. Women were excluded if they were currently pregnant or nursing. Individuals were compensated for their participation. The University of Colorado Human Research Committee approved all procedures.
