After completing a telephone screen, which included questions concerning the quantity and frequency of marijuana use, use of other recreational drugs and use of psychotropic medications, participants were invited to the laboratory for the first session of the study. Participants were instructed not to drink any alcohol 24 hours prior to, or smoke any marijuana 6 hours prior to, their session. Upon arrival to the laboratory, participants read and signed an informed consent form and provided a cheek cell and saliva sample for DNA analysis. Individuals were also breathalyzed to ensure that they had not recently used alcohol. In addition, they gave a urine sample in order to obtain a baseline THC level. Finally, participants completed a series of questionnaires pertaining to their drug use patterns, personality and mood. After this session was completed, they were scheduled to come back to the laboratory 5 days later to complete the second session of the study. They were instructed not to smoke any marijuana between the two sessions and were informed that a urine toxicology screen would be performed to confirm their abstinence.
