Psychosis / Schizophrenia

Association between non-medical cannabis legalization and emergency department visits for cannabis-induced psychosis, 2023, July 27

ICD codes with the DMS-5

F12.15 Cannabis abuse with psychotic disorder

F12.150 …… with delusions

F12.151 …… with hallucinations

F12.159 …… unspecified

Impact of cannabis legalization on healthcare utilization for psychosis and schizophrenia in Colorado, 2022, June

A Cannabinoid Hypothesis of Schizophrenia: Pathways to Psychosis

High potency cannabis products, which are increasingly accessible to children and adolescents worldwide, produce a diversity of deleterious effects on the developing brain. States that have medicalized, decriminalized, and legalized cannabis have observed softened attitudes, increased acceptance, expanded indiscriminate use, and increased rates of hospitalization for first-episode psychosis.42,43 Understanding the putative pathways for cannabis-induced psychosis might lead to targeted therapeutic interventions. Disseminating scientific information concerning the broad spectrum of cannabis-induced cognitive deficits and risks of enduring serious mental illness might prevent the onset of schizophrenia in susceptible individuals.

Adolescent cannabis use and later development of schizophrenia: An updated systematic review of longitudinal studies


Both high- and low-frequency marijuana usage were associated with a significantly increased risk of schizophrenia. The frequency of use among high- and low-frequency users is similar in both, demonstrating statistically significant increased risk in developing schizophrenia.

Development Over Time of the Population-Attributable Risk Fraction for Cannabis Use Disorder in Schizophrenia in Denmark

Conclusions and Relevance  The results from these longitudinal analyses show the proportion of cases of schizophrenia associated with cannabis use disorder has increased 3- to 4-fold during the past 2 decades, which is expected given previously described increases in the use and potency of cannabis. This finding has important ramifications regarding legalization and control of use of cannabis.

Cannabis use in adolescence and risk of psychosis: Are there factors that moderate this relationship? A systematic review and meta-analysis

Conclusion: Adolescent cannabis use is associated with an increased risk for psychosis later in life. In addition, there are factors that moderate this relationship; therefore there is a need for research to assess the interaction between these factors, adolescent cannabis use and psychosis risk.

Nurture Over Nature: Environment Plays Greater Role in Teen Psychosis

Genetics contributed less with more exposures to environmental risk factors, research suggests

Environmental risk factors may play a larger role than genetic factors in the development of psychotic experiences in adolescents, according to a twin study in Europe.

Among over 11,000 twin pairs, the relative contribution of genetic influences to cognitive disorganization was 47% in those with no exposure to environmental risk factors — such as bullying, dependent life events, cannabis use, tobacco use, or low birth weight — compared with 32% in those with these exposures, reported Angelica Ronald, PhD, of Birkbeck University of London in England, and co-authors in JAMA Psychiatry.

Geographical variation in hospitalization for psychosis associated with cannabis use and cannabis legalization in the United States: Submit to: Psychiatry Research

There was a significant correlation between the cannabis legality score and proportion of hospital discharges for psychosis associated with cannabis use (r = 0.67, p<0.05). In conclusion, we observed a higher proportion of hospital discharges for psychosis associated with cannabis use in areas with more liberal cannabis legalization laws.

Cannabis use in children and adolescents with first episode psychosis: influence on psychopathology and short-term outcome (CAFEPS study)

Conclusions: Cannabis use may be related to higher positive symptom scores for FEP patients, with greater improvement after six months for those who cease using cannabis.

Is it true that marijuana triggers transient psychotic episodes?

Dr. Christine Miller

Yes. Even with the low-strength pot common in the last century, 15% of users reported psychotic episodes:
But the proof would have to await studies in the clinic, where it was found that administration of a moderate dose of pure THC would elicit transient psychotic symptoms in study subjects:

Is there also a link to chronic psychosis (schizophrenia) in adolescent use?

Yes, and not just in adolescents. For a long while, the psychiatric community was unsure of the causal basis for the connection because studying cause and effect is a complicated endeavor. It was important to find out if there was a greater effect at a higher dose, which would indicate causality, and such a relationship was confirmed:

Another element of the causal connection was to determine which came first, the marijuana use or the psychosis:

Those at the forefront of such studies were eventually convinced that the association was causal:
The consensus is that use of marijuana with a THC content over 10% increases the risk of a psychotic disorder by 4 to 5-fold:

How does marijuana compare to other drugs that are associated with psychosis (LSD,
cocaine, amphetamine, methamphetamine, PCP)?

Marijuana is more likely to lead to chronic psychosis than any other drug studied. About half of those who experience a marijuana-induced psychotic break will eventually develop a schizophrenia spectrum disorder:

Does having schizophrenia in your genetics mean that you would have manifested the
disorder anyway?

No one is predestined to develop schizophrenia based on their genetics. Even if you have an
identical twin who develops schizophrenia, only about half the time will the other twin develop schizophrenia as well. Environmental factors, like marijuana, can make the difference between leading a normal life and not.
For clinical studies showing that THC can cause psychotic symptoms in people with no family history, see:

In Denmark, they found that for those who experienced psychosis from marijuana, a family history of psychosis did not determine who progressed to developing schizophrenia; very many became schizophrenic from marijuana without having a family history:

Is there an age where it is MORE risky to develop mental illness, such as 13 or 15?

In the case of bipolar disorder, an early age of onset is more commonly seen in those with a family history of the disease:
and, those early onset cases have been reported to be more severe than adult onset cases:
However, for schizophrenia, original findings of a worse prognosis when the diagnosis occurs as early as thirteen years of age:
have now been challenged by a much larger and more recent study, showing that early onset schizophrenia does not carry a worse prognosis:

For drug-induced mental illness, while there is some data showing use of marijuana at those young ages is more likely to lead to chronic mental illness because the brain is still developing, this does not mean it is safe to begin use after the teenage years. A recent study in Europe demonstrated that frequency of use, no matter what the age when use began, was the most significant risk factor for a psychotic break:
Irrespective of the age when a marijuana-induced psychotic break occurs, ceasing use is crucial to improving the odds of recovery (about 50% can recover):

Association of High-Potency Cannabis Use With Mental Health and Substance Use in Adolescence

Results  Past-year cannabis use was reported by 1087 participants (580 women; mean [SD] age at onset of cannabis use, 16.7 [3.0] years). Of these, 141 participants (13.0%) reported the use of high-potency cannabis. Use of high-potency cannabis was associated with increased frequency of cannabis use (adjusted odds ratio [AOR], 4.38; 95% CI, 2.89-6.63), cannabis problems (AOR, 4.08; 95% CI, 1.41-11.81), and increased likelihood of anxiety disorder (AOR, 1.92; 95% CI, 1.11-3.32). Adjustment for frequency of cannabis use attenuated the association with psychotic experiences (AOR 1.29; 95% CI, 0.67-2.50), tobacco dependence (AOR, 1.42; 95% CI, 0.89-2.27), and other illicit drug use (AOR, 1.29; 95% CI, 0.77-2.17). There was no evidence of association between the use of high-potency cannabis and alcohol use disorder or depression.

Conclusions and Relevance  To our knowledge, this study provides the first general population evidence suggesting that the use of high-potency cannabis is associated with mental health and addiction. Limiting the availability of high-potency cannabis may be associated with a reduction in the number of individuals who develop cannabis use disorders, the prevention of cannabis use from escalating to a regular behavior, and a reduction in the risk of mental health disorders.

The Bradford Hill Analysis of Causation Applied to Cannabis Use and
the Development of Chronic Psychotic Disorders
Christine L. Miller, Ph.D., Catherine Antley, MD and Dean Whitlock (editor)
with a review and contributions from Carsten Hjorthoj, Ph.D., Associate Professor,
Copenhagen Research Center for Mental Health, University of Copenhagen

Before Maryland legalizes marijuana it should consider this: Pot is linked to psychosis

By Christine L. Miller

Baltimore Sun

Apr 18, 2019 

As Maryland legislators appointed to the “Cannabis Workgroup” begin their study of the pros and cons of marijuana legalization, they should pay particular attention to the mental health risks of this drug. Unfortunately, they may not have heard much about the epidemiology of psychosis associated with marijuana use, since relevant U.S. expertise lags behind Western Europe, Canada and a couple of countries in the southern hemisphere.

Epidemiological studies are observational, not interventional, so our slow entry into the field has nothing to do with the illegal status of marijuana. Instead, I would point to our lack of centralized health care, which would otherwise facilitate collection of data on large populations — data pertaining to health status, history of health-related habits and key demographics. Another factor is how biomedical research here is tightly coupled to the pharmaceutical industry, a sector less interested in environmental factors that cause disease than in developing blockbuster drugs.

From the perspective of many of us who have researched the causes of psychosis in the laboratory or in clinical settings, the book by journalist Alex Berenson “Tell Your Children the Truth About Marijuana, Mental Illness, and Violence” provides an important wake-up call for America. The former New York Times business reporter wrote it after his psychiatrist wife suggested he learn more about the topic. But it’s a lone voice of caution on the national stage. While Medical associations in the U.S. have issued position papers citing harms of marijuana, these documents are largely buried in their websites out of view.

Here’s what you should know: Researchers looking for a dose-response correlation found that the heavier the marijuana use, and the more potent the product, the more likely a psychotic outcome like schizophrenia. Daily use of potencies considered moderate by current U.S. standards increases risk 4– to 5-fold.

Some will argue that individuals with psychosis who use marijuana are merely self-medicating pre-existing symptoms, despite research showing symptoms remit for many who quit using, and return if they use again. Studies in Europe and New Zealand of thousands of teens followed through young adulthood, demonstrated the marijuana habit preceded psychosis in the majority of marijuana users who developed it.

Yes, initial psychotic symptoms associated with marijuana are usually temporary, and only 12 percent to 15 percent of users reported these transient symptoms with lower strength marijuana common in the 1900s — symptoms like paranoia, delusions or auditory hallucinations. But 35 percent of those who experience such occasional symptoms can be expected to transition to a full psychotic break, a cluster of intense symptoms happening at once

Three studies from Finland and Denmark, again totaling thousands of subjects, further demonstrated that nearly half of those who experience a psychotic break from marijuana progress to actual schizophrenia, a progression shown to be independent of a familial history of psychosis.