DronabinolAppetite StimulantsCannabinoid Receptor AgonistsMarijuana SmokingAnorexiaPain PerceptionCannabisMarijuana AbusePsychotropic DrugsPlacebo EffectAnalgesics, Non-NarcoticSubstance Withdrawal SyndromeDouble-Blind MethodCross-Over StudiesSleepEatingDrug Administration ScheduleDose-Response Relationship, DrugTreatment Outcome