Psychosis / Schizophrenia

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
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?

Dr. Christine Miller

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 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)?

Dr. Christine Miller

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?

Dr. Christine Miller

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,
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?

Dr. Christine Miller

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.

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

Sarah Kanana Kiburi 1 2Keneilwe Molebatsi 3 4Vuyokazi Ntlantsana 4Michael T Lynskey 5Affiliations expand

Previous research has reported increased risk for psychosis among individuals who use cannabis during adolescence. We conducted a systematic review and meta-analysis to investigate the interaction between adolescent cannabis use and other factors in moderating risk for psychosis later in life. Method: We searched four electronic databases in June 2020 for articles that assessed adolescent cannabis use, had psychosis as an outcome and analyzed for the association between adolescent cannabis use and psychosis. Analysis was done using random-effects meta-analysis and narrative synthesis. Results: A total of 63 studies were included in the narrative review and 18 studies were included in the meta-analysis. Adolescent cannabis use was found to increase risk for psychosis (RR = 1.71 (95%CI, 1.47-2.00, p < 0.00001) and predict earlier onset of psychosis. The following factors moderate the relationship between cannabis use and the risk of psychosis: age of onset of cannabis use, frequent cannabis use, exposure to childhood trauma, concurrent use of other substances and genetic factors. 

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.