RCT of CBD for Anxiety in Advanced Breast Cancer

Inclusion Criteria: * Diagnosis of Stage IV or metastatic breast cancer * Age ≥18 years. * ECOG performance status ≤2 (Karnofsky ≥60%). * Participants must have adequate organ and marrow function at baseline as defined below: * total bilirubin \>2 times institutional upper limit of normal (ULN) * AST(SGOT)/ALT(SGPT) ≤3 × institutional ULN * Baseline anxiety as measured by GAD-7 ≥5 * At least mild anxiety typically experienced prior to oncologic scans (as measured by a prescreen survey item) * Computed tomography (CT) or positron emission tomography (PET) to assess tumor burden scheduled for within 48 hours of study drug administration * No cannabis, delta-9-tetrahydrocannabinol or cannabidiol use within 24-hours of study drug administration. * No benzodiazepine consumption within 8 hours of study drug administration (e.g.,nighttime benzodiazepine use permissible) * No driving for 12 hours following study drug administration. * English proficiency * The effects of cannabidiol (Epidiolex) on the developing human fetus are unknown. For this reason and because cannabis is known to be teratogenic, women of child-bearing potential must test as nonpregnant prior to entering the study. The study team will encourage women of child-bearing age and men to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she should inform her treating physician immediately. Men treated or enrolled on this protocol must also agree to use adequate contraception prior to the study, for the duration of study participation, and for 1 week after cannabidiol (Epidiolex) consumption. Women either age \> 54 years or documented to be in menopause or status post hysterectomy will not be required to obtain bHCG. * Ability to understand and the willingness to sign a written informed consent document. Exclusion Criteria: * History of allergic reactions attributed to compounds of similar chemical or biologic composition to cannabidiol (Epidiolex) or placebo (which contains sesame, corn and gluten) * History of current clobazam or valproic acid use * Current uncontrolled illness, for instance sepsis, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia * Current use of antiretroviral therapy * Participants with psychiatric illness or social situations that would limit compliance with study requirements * Current hepatocellular carcinoma, or documented history of difficult to control diabetes -- Active participation in a clinical drug trial