Guanfacine Extended-release for Adolescents With Cannabis Use

Inclusion Criteria: 1. 12-25 years of age (inclusive) at consent; 2. Seeking treatment for cannabis use; 3. DSM-5 Cannabis Use Disorder, mild, moderate or severe; 4. Self-reported cannabis use on average at least 5 days/week during the 28 days prior to screening with a THC positive urine drug screen on the day of screening; and 5. Able to provide informed consent (both adequate IQ and English fluency; \<18-year-olds will provide consent themselves in addition to parent/guardian consent). Exclusion Criteria: 1. DSM-5 substance use disorder (moderate or severe) except cannabis or nicotine; 2. Any unstable medical, psychiatric or neurological condition or medical contraindicating study participation; 3. Diagnosis of a psychotic or bipolar illness; 4. Acute suicidality as assessed by clinician; 5. Prescribed antipsychotics, benzodiazepines or other sedative medications, or other medications for the treatment of ADHD. If prescribed antidepressants, the participant must have been on a stable dose for more than 2 weeks at screening; 6. A history of heart disease or cardiac risk factors (e.g. arrhythmias); 7. Abnormal liver or thyroid function as indicated by clinically-significant findings on blood tests; 8. Pregnancy, breast feeding or, if sexually active and able to become pregnant, no effective contraception. 9. Intention to enter residential rehabilitation after treatment in the YSAS residential withdrawal facility.