All participants will be healthy volunteers and all procedures will be completed for research purposes only. Two groups will be recruited, females who use cannabis (marijuana, MJ), and female who do not use cannabis (controls). Female MJ users will be enrolled in a protocol that includes an outpatient drug administration session and a 4-day/3-night inpatient stay on the Johns Hopkins Bayview Clinical Research Unit (CRU). During outpatient visits, MJ users will have an MRI, and complete MJ self-administration and cognitive performance sessions. MJ users will then reside on the CRU,and complete MJ abstinence, and self-report instruments for withdrawal discomfort. A positron emission tomography (PET) scan of brain cannabinoid type 1 receptors will also be completed. Non-users will complete MRI, PET imaging and cognitive testing under an outpatient protocol (no MJ administration).