New Research Links Marijuana Use with Psychosis–Part 1

Clinicians have long known that marijuana use–especially in the teenage years while the brain is still developing–causes degraded cognitive capacity, loss of motivation, memory loss, and paranoia. However, researchers are now discovering further evidence that marijuana use leads to an increased risk of developing psychotic disorders–including schizophrenia (Robertson & Swartz, 2019). Moreover, it’s not only youth who are at greater risk. The May 2017 edition of the journal Psychiatric Services reported that there is an increase in adults over the age of 30 in the U.S. being diagnosed with psychotic disorders (as cited by Berenson, 2019).

Why the increases in diagnoses of psychosis? At least part of the answer is likely due to the combined effects of the presence of more potent marijuana, legalization of marijuana use at the state level in many regions, and a prevailing national attitude that “marijuana is simply not that bad.” The science on this topic provides strong evidence to the contrary. [It’s important to note that marijuana possession and distribution remains illegal at the federal level, and this applies to all 50 states.]

The psychoactive component of the marijuana plant is the chemical delta-9-tetrahydrocannabinol–commonly known as THC (Berenson, 2019). Although marijuana has been utilized for thousands of years, it’s usage in the U.S. increased in the 1960s and 1970s. However, the THC content of marijuana at that time was commonly less that two percent (Berenson, 2019). Today, the THC content of marijuana purchased in “legal” dispensaries is routinely 25% (Berenson, 2019). It is difficult to overstate the negative effects and danger which this increase in THC content poses to today’s marijuana consumers.

Research which correlates marijuana use and psychosis suggests that “adolescent marijuana use raises the risk of schizophrenia between two- and six-fold” (Berenson, 2019, p. xxxiv). This data must be shared with every parent, educator, student, and policy-maker in the nation.

The epidemic isn’t coming–it’s already here. More to follow in part 2.


Berenson, A. (2019). Tell your children: The truth about marijuana, mental illness, and violence. New York, NY: Free Press.

Robertson, A. G., & Swartz, M. S. (2019). Thinking carefully about marijuana legalization: Public health considerations for state policy makers. Psychiatric Services, 00, 1-2. doi: 10.1176/

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