6. Once a month the investigators will visit each participant at their home. Prior to the visit, the participant will inform the investigators about the timing of their smoking to ensure that the blood draw with sodium heparin will occur no later than 15 min after smoking to ensure measurable THC, THC metabolites, CBD and CBN (cannabinol) levels. Blood THC, CBD and CBN content, along with THC phase I metabolites 11-OH-THC (active 11-hydroxy-THC) and THC-COOH (inactive 11-nor-9- carboxy-THC) will be determined using liquid chromatography-mass spectrometry in the Department of Chemistry under the direction of Dr. Denef. These values will inform on the participant's blood cannabinoid profile and the relative contents of non-psychoactive CBD and CBN versus psychoactive THC and its metabolites. Importantly, at each home session, participants will be asked about adverse effects and allergies related to marijuana.