Inclusion Criteria:  Monozygotic (MZ) twin pair, in which both twins are willing to participate MZ twin pair must be concordant in their frequency of cannabis use (+/- 2 days) Cannabis use at least 1x per week on most weeks Cannabis use in the past 7 days at the baseline visit Positive qualitative urine toxicology at baseline for THC Located within the state of Colorado  Exclusion Criteria:  1) Discordance in the twin pairs on a significant, adverse experience, like traumatic brain injury.