BY DONALD R. RICE, MD, CHAIR, MMS COMMITTEE ON MENTAL HEALTH AND SUBSTANCE USE, AND AMY TURNCLIFF, PHD, ADVISOR TO THE MMS COMMITTEE ON MENTAL HEALTH AND SUBSTANCE USE
When Massachusetts entered the era of recreational cannabis commercialization nearly a decade ago, a rise in cannabis-related health concerns seemed likely. At the time, the scientific literature — including two influential articles (Adverse Health Effects of Marijuana Use and Effects of Cannabis Use on Human Behavior, Including Cognition, Motivation, and Psychosis: A Review) co-authored
by Nora Volkow, MD, Director of the National Institute on Drug Abuse — outlined known adverse health effects of marijuana use while acknowledging important gaps in evidence. What was less anticipated was the growing incidence of cannabis-induced psychosis (CIP) linked to high-potency products, with average THC concentrations now four times higher than in the 1990s.
From Clinical Observation to Lived Experience
A modifiable risk factor
Across multiple studies, use of high-potency cannabis has emerged as a modifiable risk factor for acute psychosis. Risk increases sharply with younger age, higher frequency of use, high THC concentration, and pre-existing mental health concerns. Although CIP is most common in young adults, cases can occur across the lifespan and in individuals
with and without known psychiatric vulnerability.
Clinical presentation
Patients with CIP often present with sudden onset of paranoid or persecutory delusions, hallucinations, prominent anxiety, agitation, and mood lability. Distinguishing
CIP from a primary psychotic disorder can be challenging, as symptoms often overlap, and cannabis may obscure underlying vulnerabilities. However, a clear temporal relationship between THC use and symptom onset, rapid improvement with abstinence,
and the absence of baseline psychotic symptoms can help guide diagnosis.
Conversion and precipitation
Cannabis use has been associated with more cases of psychosis and earlier onset of schizophrenia, strongly suggesting a causal relationship. Data suggest that nearly half of individuals
with CIP later develop schizophrenia or bipolar disorder — either through precipitation of a forthcoming psychiatric illness or conversion of CIP to a chronic illness. Early identification and prompt cessation of THC use substantially reduce this
risk, highlighting the importance of screening and timely intervention.
Impact on existing serious mental illness
For patients with known schizophrenia, bipolar disorder, or other serious mental illness, ongoing cannabis use — particularly high-potency use — can destabilize symptoms, increase
relapse risk, and impair functioning. Reducing or discontinuing cannabis often leads to clinical improvement, making early discussion and monitoring critical.
Population trends
In regions where high-THC products are widely available, cannabis appears to contribute substantially to the incidence of first-episode psychosis. Thirty to fifty percent of new psychosis cases in some international cities may be attributable to cannabis
use. In Canada, the proportion of incident cases of schizophrenia associated with cannabis use disorder almost tripled during a period of substantial liberalization of cannabis
policy. Early signs of similar trends are emerging in Massachusetts. Adolescents presenting to psychiatric emergency services have shown increases in THC positivity, and Boston-area
data link THC-positive screens with greater severity of acute psychosis, including higher rates of agitation requiring medication or restraint.
What Physicians Can Do
As cannabis products become more potent and more accessible, physicians across specialties have a growing role in identifying cannabis-related health impacts and preventing progression to more serious conditions like CIP. Practical steps include the following:
- Ask routinely about cannabis use, including product type (THC/CBD), potency, mode of consumption, and frequency.
- Educate patients, especially adolescents and young adults, on the risks of high-THC products, including addiction, cannabis-induced psychosis, cannabinoid hyperemesis syndrome, and mood destabilization.
- Code for cannabis-related diagnoses to improve tracking of clinical trends and ensure appropriate follow-up.
- Encourage reduction or abstinence when patients report negative cannabis-related health impacts and refer to addiction treatment when indicated.
- Arrange prompt referral for CIP, ideally to clinicians experienced in dual-diagnosis care.
Physicians increasingly find themselves guiding patients through a cannabis landscape that has changed faster than public perception of its risks. The good news is that CIP is often reversible, particularly with early recognition and intervention. By
integrating cannabis screening into routine care and by responding promptly to cannabis-related psychiatric symptoms, physicians can improve long-term health outcomes for patients.
