Effects of Dronabinol in Opioid Maintained Patients

Inclusion Criteria:

* Prior exposure to THC or cannabis at least once in the last 10 years; 1-10 times in the last 20 years; or more than 20 times in their lifetime.
* Males and females, Veterans and non-Veterans, aged between 18 and 70.
* Diagnosed with OUD and currently enrolled in methadone or buprenorphine maintenance treatment.
* Capable of providing informed consent in English.
* Compliant in opioid maintenance treatment and on a stable dose for two weeks or longer.
* Not meeting DSM-5 criteria for substance use disorders other than OUD or tobacco use disorder within the last 12 months.
* No current medical problems deemed contraindicated for participation by principal investigator.
* For women, not pregnant as determined by pregnancy screening; not breast-feeding; using acceptable birth control methods.

Exclusion Criteria:

* Currently meeting DSM-5 criteria for cannabis use disorder (CUD).
* History of primary psychotic disorders or other current major psychiatric disorders deemed clinically unstable by the principal investigator.
* Serious medical or neurological illness or treatment for a medical disorder that could interfere with study participation as determined by principal investigator.
* Inability to complete neuropsychological tests.
* A physician will carefully evaluate participants for use of over-the-counter or prescription psychoactive drugs known to affect pain threshold or pain tolerance (including NSAIDS, serotonin-norepinephrine reuptake inhibitors (SNRIs), (e.g. venlafaxine, duloxetine), tricyclic antidepressants (e.g., nortriptyline, amitriptyline), anticonvulsant medications (e.g., topiramate, tegretol), benzodiazepines (e.g., alprazolam, diazepam), and other opioid drugs). Only subjects who are on stable doses of these medications, and whose dosing schedules allow participation in the study visits, will be enrolled. If possible, the morning dose will be administered after the study visit.
* Liver function tests (ALT or AST) greater than 3x normal.
* Contraindications for exposure to cold temperatures, such as Raynaud's phenomenon and hypertension.
* Allergy or serious adverse reaction to cannabis, dronabinol or other cannabinoids.