Cannabis and its potential link to psychosis has been a hot-button topic for the last two decades. Cannabis produces cannabinoids that mimic endocannabinoids, which the body uses to regulate neural signaling throughout the brain. And the endocannabinoid system is widely distributed throughout parts of the brain responsible for regulating mental health. Therefore, it should not be surprising that a plant cannabinoid such as THC might be capable of interfering with brain function to a degree that could mimic psychosis. An overdose of THC is certainly capable of producing a short-lived psychotic break. Whether this adverse event could cause lasting damage is not known. It is commonly held that THC is psychoactive and CBD is non-psychoactive. But whether THC causes psychosis and schizophrenia remains controversial. There has been endless scientific debate about whether cannabis use is a causal factor in the development of schizophrenia and other psychotic disorders.150 A tenuous link between cannabis use and the incidence of psychotic disorders appeared to have been established, but confidence is now quite low that the development of mental illness is solely due to cannabis use.151 There is increasing evidence that THC tends be pro-psychotic and CBD is antipsychotic. These oppositional effects have been demonstrated by brain imaging. In nearly every region of the brain associated with psychosis, THC tends to elicit a pro-psychotic effect, while CBD produces the opposite.152 Because of this propensity toward eliciting psychotic symptoms, high-THC cannabis is believed to be linked to increased risk of psychosis, especially in the developing adolescent brain.153 Higher CBD content of cannabis is linked to a reduction in psychotomimetic effects.154 All of this does not mean that high-THC cannabis will trigger psychosis—but rather it increases its risk, which remains very small. What is increasingly clear though is that the cannabinoid ratio of today’s cannabis is skewed completely toward THC, when for hundreds of years it was 50/50 THC and CBD. The imbalance of today’s cannabis is the result of a prohibition that favored psychoactive potency.155 In an interesting study by Celia Morgan and Valerie Curran of the Clinical Psychopharmacology Unit of University College London, hair samples were taken from a group of individuals undergoing a longitudinal study for past drug use. The hair samples were tested for their residual cannabinoid content and the results divided by whether the hair contained THC only, THC and CBD, or no cannabinoids. The participants were then given a test that measures proneness toward psychosis. The results show higher levels of unusual experiences—akin to hallucinations and delusions associated with psychosis—in individuals who had only THC in their hair compared with those with THC and CBD, and those with no cannabinoids.156
SCHIZOPHRENIA
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