Varenicline Treatment for Cannabis Use Disorder

General Inclusion Criteria

• Must meet DSM-5 criteria for cannabis use disorder and use cannabis at least 3 days per week in the last 30 days.
• Must be between the ages of 18 and 65 years.
• If female and of childbearing potential, must agree to use acceptable methods of birth control for the duration of the trial.
• Must consent to random assignment, and be willing to commit to medication ingestion.
• Must be able to read and provide informed consent.
• Must have body weight >110lbs (50kg) and have BMI between 18 and 35kg/m2
• Must function at an intellectual level and have knowledge of the English language to sufficiently allow for accurate completion of assessments.

Additional Inclusion Criteria for fMRI Eligibility

• Must be right-handed.

General Exclusion Criteria

• Women who are pregnant, nursing, or plan to become pregnant during the course of the study.
• Individuals with severe renal impairment (creatinine clearance less than 30 mL per minute).
• Lifetime history of DSM-5 Bipolar I or II Disorder, Schizophrenia or other psychotic disorder. Stably treated MDD, Dysthymia, GAD, Social Phobia, and Specific Phobia diagnoses are acceptable (i.e. same dose of medication has been prescribed for at least 2 months prior to screening and no changes in current medication expected during course of the trial).
• Suicidal ideation or behavior within the past 6 months. Subjects who are believed to be at suicidal or homicidal risk (answers 'yes' on questions 4 or 5 of C-SSRS) will be referred for assessment by a qualified mental health professional.
• Concomitant use of psychotropic medications, with the exception of stable doses (defined as no dosing adjustments in the past two months) of non-MAO-I antidepressants, non-benzodiazepine anxiolytics, and ADHD medications.
• Current use of medications prescribed for mania or psychosis.
• Current use of buproprion or nortryptiline.
• Moderate or severe non-cannabis substance use disorders within the past 60 days with the exception of tobacco use disorder.
• Individuals taking an investigational agent within the last 30 days before baseline visit.
• Individuals with clinically significant medical disorders or lab abnormalities.
• Any individual at screening with SGOT (AST) or SGPT (ALT) greater than 3 times the upper limit of normal and/or total bilirubin greater than two times the upper limit of normal.
• Individuals with clinically significant cardiovascular disease in the past 6 months (e.g., myocardial infarction, CABG, PTCA, severe or unstable angina, serious arrhythmia, or any clinically significant ECG conduction abnormality.
• Individuals with clinically significant cerebrovascular disease in the past 6 months such as TIA, CVA, or stroke.
• Hypersensitivity to varenicline.
• Individuals who have participated in the clinical trial of any investigative compound within the last 60 days.

Additional Exclusion Criteria for fMRI Eligibility

• Any psychiatric or medical issues, including claustrophobia, ferrous metal implants, pacemakers, or other electronic devices that would interfere with ability to participate in and successfully complete scanning procedures.
• Any person unable to lie still within the fMRI scanner for the required period of time to obtain useful images (use of anxiolytics will not be permitted for anxiety/claustrophobia related to scanning procedures).