Cannabis Use Disorder, Mild

This research study evaluates the effects of an FDA-approved medication Gabapentin in individuals with Bipolar Disorder who smoke marijuana. Participants in the study will will be assigned to take either Gabapentin or a matched placebo. Study medication will be taken for 17 days. There will be 5 study visits, with 2 MRI brain imaging scans completed. Questionnaires and clinical interview measures will be completed at study visits along with consistent assessment of potential side effects from study medication.