Understanding Effects of Cannabis Use and Abstinence on Neural Glutamate Homeostasis

This study will be the first in vivo human multimodal neuroimaging study exploring the relationship between mGluR5 availability (PET), neural oscillations (EEG), and cognitive function in people with CUD. The goal is to test the overall hypothesis that mGluR5 availability is higher in people with CUD compared with HC. In Aim 1, the investigators will determine differences in mGluR5 availability between people with CUD and HC in the fronto-limbic brain circuit. Aim 2 examines the associations between mGluR5 availability, CUD severity, neural oscillations, and cognitive function in CUD subjects. Aim 3 will determine how prolonged abstinence from chronic cannabis use affects mGluR5 availability, neural oscillations, and cognitive function in CUD subjects.

Inclusion Criteria:HC and CUD Group:Voluntary, written, informed consentPhysically healthy by medical history, physical, neurological, ECG and laboratory examsNo personal or first-degree relative history of psychiatric disorders (outside of cannabis use for CUD group)Full scale and verbal IQs > 80 (Wechsler Adult Intelligence Scale, Fourth Edition; WAIS-IV).CUD group:Cannabis use disorder as determined by DSM-5 structured interviewsUrine toxicology evidence of cannabinoid useHC group:lifetime cannabis exposure less than 20 timesno cannabis use in the past 2 years by self-reporta negative urine drug screen.Exclusion Criteria:Other substance use disorder within 1 year, except for nicotineAnother primary DSM-5 Axis I major psychiatric disorder (e.g., schizophrenia, bipolar disorder, major depression, etc.) per SCID-5Urine toxicology results positive for other drugs such as opiates / opiate metabolites (e.g., methadone, buprenorphine, etc.)A history of significant medical (cardiac, infectious, metabolic) or neurological illness (e.g., cerebrovascular disease, traumatic brain injury)A history of seizures/epilepsyCurrent use of psychotropic and/or potentially psychoactive prescription medicationsMedical contraindications to MRI imaging (e.g., ferromagnetic implants/foreign bodies, claustrophobia, etc.)Pregnancy or breastfeeding (women).Subjects will be excluded for major medical or neurological illness or laboratories consistent with these illnesses or suggesting contraindication to PET or MR imaging