Cannabis and Mental Health
May 28, 2026
At the May CMCR Investigators’ Meeting, Garth Terry, M.D., Ph.D., of the VA Puget Sound and University of Washington School of Medicine, and Deepak Cyril D’Souza, M.D., Professor of Psychiatry at Yale School of Medicine and staff psychiatrist at VA Connecticut Healthcare System, presented an evidence-based overview of cannabis use and mental health. Their talk drew on a recent JAMA Internal Medicine article they co-authored aimed at helping primary care clinicians, internists, and psychiatrists discuss cannabis use with patients.
Dr. Terry briefly reviewed the changing cannabis landscape, including rising use, diverse product types, and wide variation in THC exposure by route of administration. Smoked cannabis produces rapid onset and washout, while oral THC has slower onset, longer duration, and metabolism to 11-hydroxy-THC. He also reviewed the broad distribution of CB1 receptors in the brain and the role of the endocannabinoid system in regulating neurotransmission. These points served mainly as background for the central clinical question: how cannabis use relates to psychiatric symptoms and disorders.
For mood disorders, the presenters emphasized that evidence does not support cannabis as an effective treatment. In depression, cannabis use has not been associated with remission and may be associated with worse symptoms. In bipolar disorder, cannabis use has been linked to worse mania, lower recovery and remission, and greater recurrence or relapse. For anxiety disorders, cannabidiol may have anxiolytic effects, but the evidence remains low certainty. THC has mixed and uncertain effects, with higher doses tending to worsen anxiety.
PTSD was highlighted as a condition in which patients may perceive short-term symptom relief, particularly for nightmares, sleep disturbance, pain, or avoidance-related distress. However, clinical trial evidence does not show meaningful improvement in overall PTSD severity, functioning, or mental health outcomes. Cannabis use may also interfere with fear extinction and evidence-based treatments, while withdrawal symptoms can overlap with PTSD symptoms and reinforce continued use.
Dr. D’Souza focused on psychosis, distinguishing transient psychotic symptoms during intoxication, cannabis-induced psychosis lasting beyond intoxication, and the later emergence of persistent psychotic disorders such as schizophrenia. He reviewed experimental and epidemiologic evidence showing that THC can induce psychotic symptoms, worsen symptoms in people with schizophrenia, and increase risk among vulnerable individuals, particularly with frequent or high-potency use. The presenters also discussed ADHD, cannabis use disorder, cognition, withdrawal, and medication interactions. They concluded that clinicians should ask routinely and nonjudgmentally about cannabis use, counsel high-risk patients carefully, discuss withdrawal, discourage smoked cannabis, and approach high-THC products with caution. To hear more on this topic, listen to the High5 episode with Dr. D’Souza.
Garth Terry, PhD
Dr. Terry is a Psychiatrist Investigator in the Mental Illness Research, Education, and Clinical Center (MIRECC) at VA Puget Sound, and Assistant Professor in the Departments of Psychiatry and Behavioral Sciences, and Radiology at University of Washington School of Medicine. His areas of research interest are in novel radioligand development and their application in neuropsychiatric conditions, including ones for the cannabinoid CB1 receptor, and clinical studies involving cannabis and cannabinoids.
Deepak Cyril D’Souza, MD
Dr. D’Souza is a Professor of Psychiatry, Yale University School of Medicine and a staff psychiatrist at VA Connecticut Healthcare System (VACHS). He received his medical degree from John’s National Academy of Health Sciences, Bangalore, India in 1986 and completed his psychiatric residency at State University of New York Downstate in 1992 followed by a postdoctoral fellowship in Psychopharmacology and Neurosciences at Yale University School of Medicine. He then joined the faculty in the Dept. of Psychiatry at Yale and VA Connecticut Healthcare System. He is an active clinician, teacher and researcher, 30 years of experience.