August 24, 2021 | Jerry Bergman

Cannabis Use Linked to Mental Disorders

Marijuana use linked to schizophrenia and psychosis:
Why would God create a harmful plant?


by Jerry Bergman, PhD

New research is increasingly supporting the premise that the effects of cannabis, commonly called marijuana, can be very harmful to health. One significant study from 2012 was published in the leading American medical journal, the Journal of the American Medical Association (JAMA). The research provided further support for the conclusion that the mind-altering drug marijuana is an important factor influencing the onset of schizophrenia. Scientists in Denmark used a nationwide, register-based cohort sample to research “the population-attributable risk fraction for cannabis-use disorder in schizophrenia” and found that it “increased from approximately 2% in the period to 1995 to approximately 6% to 8% since 2010.” [1]

Thus, the rate of schizophrenia tripled or quadrupled from the 1995 level in 15 years – an enormous increase. The results from the longitudinal analyses concluded the “proportion of cases of schizophrenia associated with cannabis-use disorder has increased 3- to 4-fold during the past 2 decades.” Thus, increases in both the use and potency of cannabis appears to cause higher levels of the horrible mind disease called schizophrenia.

This year (2021), the Society for the Study of Addiction found a connection between cannabis use and the development of opioid addiction. The meta-analysis (a study that combined the results of several different studies) found that “people who use cannabis are disproportionately more likely to initiate opioid use and engage in problematic patterns of use than people who do not use cannabis.”[2]

Why Would God Create a Harmful Plant?

My past employment history included work at a clinic that treated drug users: Alexandrine House in Detroit, Michigan. When working there, I had a number of discussions with persons addicted to marijuana. What surprised me was the range of responses to the drug. Some users became irrationally paranoid, others described the experience as close to smoking air which had virtually no effect.

With the recent legalization of recreational use of marijuana in many states, and the legalization of its medical use in most states, questions arise about the drug from a creation worldview. The main psychoactive component of cannabis is tetrahydrocannabinol (THC). One major question is, why did God create drugs such as tetrahydrocannabinol that are poisonous or mentally harmful?

It’s important to clarify what we mean by poison. Poisonous substances include anything that can physically harm us if we inhale, swallow, or touch it. They range from mosquito stings to arsenic poisoning.

The Greek word used in the Scriptures for drugs is “pharmakia” (Greek: φαρμακεία) which literally means mind-altering “drugs,” and is the source of the English word “pharmacy.” Pharmakia is translated in English Bibles as either “witchcraft” or “sorcery” because of the strong connection of mind-altering-drugs to witchcraft and sorcery, and casting of spells. Scripture condemns abuse of mind-altering drugs such as cannabis and alcohol. The concern is about anything that puts the user in a distorted state of mind.

Marijuana, Cannabis sativa (Wiki Commons)


Damaging a Sound Mind

Marijuana abuse can, in some cases, lead to transient psychosis, but can cause, or worsen, psychotic disorders like schizophrenia. The evidence from key research reports is “that marijuana use, especially in early adolescence, can lead to psychotic disorders in adulthood, such as schizophrenia.”[3]

The latest research supports this conclusion. A 2019 paper reports that psychosis was three times greater in those who used cannabis daily compared to people who never used the drug. The researchers extrapolated this finding, concluding “where highly potent cannabis was most available, the researchers calculated that …  eliminating its use would reduce psychosis rates in London by 30% and in Amsterdam by 50%.”[4]

In another meta-study from 2019, Clement and her colleagues analyzed the findings of 68 reviews of cannabis research, and fully 62 (91%) found that

associations between the drug and various adverse outcomes, including impaired driving, increased risk of stroke and testicular cancer, brain changes that could affect learning and memory, and a particularly consistent link between cannabis use and mental illnesses involving psychosis. Risks were highest for teenagers, pregnant women and people already at risk of mental illness.[5]

What Good Is Marijuana?

The few beneficial uses that exist for cannabis, apart from the intoxicating effects that make it controversial, are quite limited and vary according to individual factors. As a whole, marijuana has the potential for causing severe psychoses, supporting its classification as a dangerous mind-altering drug.[6] Scripture encourages us to have a sound mind. Enough evidence now exists to conclude the safest course by far is to avoid using the drug unless some clear medical use is warranted.[7]

The Scriptures declared all creation, including plants, to have been good. The Bible is clear: “God said, ‘Behold, I have given you every plant yielding seed that is on the surface of all the earth, and every tree which has fruit yielding seed; it shall be food for you.’”[8]

A major principle to keep in mind when interpreting the original goodness of creation is that any chemical, plant-derived and otherwise, can be abused. The dose level is the poison. This means every known chemical, both plant derived and obtained by other means, is not poisonous in small doses, but all chemicals are poisonous in large enough doses. The only exception I am aware of is dimethylmercury, which even in extremely small doses (less than 0.1 mL) is deadly poisonous.[9]

All chemicals are poisonous in large doses. That even includes water. Although necessary for life, water is lethal in large doses because it disturbs the body’s electrolytes. When water in the body exceeds safe levels, it becomes difficult for the kidneys to process it rapidly enough. The result is too high a level of body liquids, causing the mineral level balance to become too dilute. This is especially a problem when dangerously low levels of sodium result, producing hyponatremia. Drinking no more than four liters in four hours is a rough guideline, but the dangerous level depends on the climate and the person, their sex, weight, age, and health status.

How toxic a chemical is also depends on how easily it is absorbed and metabolized, and how rapidly it is expelled by the body. Furthermore, not everyone is equally affected by a specific toxic substance. Some animal species are more susceptible to various poisons; others far less susceptible to the same toxin. The classic example is, it requires 1,000 times more dioxin to kill a hamster than a guinea pig, thus the high level of guinea pig sensitivity makes them ideal for certain kinds of toxicity research.


In conclusion, Cannabis is a plant that displays clear evidence of good design but, although it is not a cure-all, it can in some cases help a few medical conditions, such as pain. But it also can have horrible side effects when abused.[10] Research has shown that heavy use of marijuana is associated with an increased risk of schizophrenia. Many experts believe that heavy pot use works in conjunction with other risk factors to trigger schizophrenia and other mental disorders.[11] Any plant can be misused or abused. This does not negate the fact that every plant-yielding seed that is on the surface of the earth, and every tree which has fruit-yielding seed, can be used as food, medicine or other purposes for humanity..[12]

Ed. comment: It’s been a different world since the judgment on sin at the Fall (Genesis 3). Creation is still mostly good, witnessing to the wisdom and glory of God, but there are also many dangers. We need to use the brains we were given. Careful observation and testing—experimental science—can help distinguish the healthful from the harmful.


[1] Hjorthøj, Carsten,  et al., 2012. Development Over Time of the Population-Attributable Risk Fraction for Cannabis Use Disorder in Schizophrenia in Denmark.

[2] Society for the Study of Addiction, 2021, Meta-analysis finds cannabis may be linked to development of opioid use disorders, Medical Xpress, July 15.

[3] Raby, Wilfrid Noël, 2013. Comorbid Cannabis Misuse in Psychotic Disorders: Treatment Strategies, Primary Psychiatry 6(4):29-34, May, p. 29.

[4]  di Forti, Marta, et al. 2019. Potent pot linked to Psychosis. Lancet Psychiatry. 6, 2019, pp. 427–436.

[5] Sohn, Emily, 2019. Weighing the dangers of cannabis. As interest builds in the potential health benefits from the plant, accumulating evidence confirms that taking the drug also carries risks, Nature 572(S16-S18):28, August.

[6] Berenson, Alex. 2019. Tell Your Children: The Truth About Marijuana, Mental Illness, and Violence. Free Press, New York, NY.

[7] Gogek, Ed, Marijuana Debunked: A handbook for parents, pundits and politicians who want to know the case against legalization, InnerQuest, New York, NY. This book was written by a medical doctor with extensive experience in treating persons addicted to drugs, and is much better documented by the scientific literature than Berenson’s book.

[8] Genesis 1:29, New American Standard Bible (NASB), 1977.

[9] Dimethylmercury is one of the strongest known neurotoxins. A quantity less than 0.1 mL is capable of inducing severe mercury poisoning. It is also easily absorbed through the skin, which creates problems in working with it. See

[10] Drew, Liam, Cannabis research round-up. Highlights from laboratory studies and clinical trials, Nature. 572(s21). August 2019, p. 29.

[11] Health Day, 2021. Could heavy marijuana use be driving rise in schizophrenia cases?, Medical Xpress, 27 July 2021.

[12] Genesis 1:29, New American Standard Bible (NASB), 1977.

Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,300 publications in 12 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,500 college libraries in 27 countries. So far over 80,000 copies of the 40 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.


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  • R2-U2 says:

    From the July 2020 article, “Is there a link between marijuana use and psychiatric disorders?” on the National Institute on Drug Abuse website (

    “The strongest evidence to date concerns links between marijuana use and psychiatric disorders in those with a preexisting genetic or other vulnerability.”

    “Research using longitudinal data from the National Epidemiological Survey on Alcohol and Related Conditions examined associations between marijuana use, mood and anxiety disorders, and substance use disorders. After adjusting for various confounding factors, no association between marijuana use and mood and anxiety disorders was found. The only significant associations were increased risk of alcohol use disorders, nicotine dependence, marijuana use disorder, and other drug use disorders.”

    Here are just 4 of 113 references for the article:

    Substance Abuse Center for Behavioral Health Statistics and Quality. Results from the 2018 National Survey on Drug Use and Health: Detailed Tables, SAMHSA.

    Office of National Drug Control Policy, National Drug Control Strategy Data Supplement 2020, Feb. 2020, p. 95, Table #77 

    Chelsea L. Shover, Corey S. Davis, Sanford C. Gordon, and Keith Humphreys, Association between medical cannabis laws and opioid overdose mortality has reversed over time, PNAS June 25, 2019 116 (26) 12624-12626.

    Di Forti M, Quattrone D, Freeman TP, et al. The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study. The Lancet 2019;6(5);427-436 

    • Thank you for writing a civil critique. Dr Bergman responds,
      “The strongest evidence to date concerns links between marijuana use and psychiatric disorders in those with a preexisting genetic or other vulnerability.” I agree, but how many people know they have a preexisting genetic or other vulnerability? If they have a problem with marijuana they can rationalize it in this way. I have worked with too many marijuana users, including family members, thus my conclusion is don’t start and you will not have a problem. Now that general use is legal in many states and as more data comes in, it appears we may regret legalizing it. Time will tell!

  • R2-U2 says:

    Jerry Bergman wrote: “Scripture condemns abuse of mind-altering drugs such as cannabis and alcohol. The concern is about anything that puts the user in a distorted state of mind.”

    In John 2, Jesus performs a miracle at a wedding in Cana. The hosts ran out of wine, and Jesus’ mother asks him to intervene. Throughout the passage, the Greek word translated “wine” is oinos — the common Greek word for normal wine, wine that was fermented/alcoholic.

  • R2-U2 says:

    Sept. 29, 2021:
    The Cannabis Question
    As state-legalized cannabis spreads, NOVA explores its little-known risks and benefits.

    • The rules prohibit sending readers to external sites.

    • R2-U2 says:

      If I am prohibited from sending readers to external sites, then for those who many not know, NOVA is seen on the PBS-TV network:

      Sept. 29, 2021:
      The Cannabis Question
      As state-legalized cannabis spreads, NOVA explores its little-known risks and benefits.
      Time: 9:00 p.m. ET/8C on PBS

      Excerpts from the press release:

      THE CANNABIS QUESTION follows scientists such as Daniele Piomelli at UC Irvine and Yasmin Hurd at Mount Sinai Hospital, who are leading research on the endocannabinoid system—a collection of chemicals and receptors throughout the brain and body that help the body maintain balance, or homeostasis. In fact, the cannabinoid receptor—named after cannabis—is the most abundant receptor in the brain. These receptors bind with our own cannabis-like molecules, called endocannabinoids, regulating key functions such as appetite, cognition, memory, and emotion. The disruption of this crucial biological system can be associated with psychiatric disorders such as post-traumatic stress disorder (PTSD). Cannabis contains over 100 cannabinoid compounds, chemicals that mimic those in our own bodies. One is THC, which produces the “high” associated with cannabis use. Another, called CBD, shows promise for treating epilepsy, opioid addiction, and anxiety.

      The film presents the current understanding about some of the potential medical benefits of cannabis, while raising questions that require more research. Along the way, viewers hear personal stories from individuals who use it medicinally to treat ailments that include side effects from chemotherapy, PTSD, anxiety, and chronic pain—helping patients cut back on the use of opioids and other pharmaceutical drugs. NOVA follows Stanford neuroscientist Catherine Jacobson who experimented with CBD extracts as a treatment for her son, whose chronic epilepsy was causing crippling seizures and was not controlled by pharmaceutical drugs. Her work helped pave the way for one of only a handful of FDA-approved cannabis-related drugs—Epidiolex, which can be prescribed to treat seizures. The film goes on to document several clinical trials around cannabis currently underway, including research investigating whether CBD could improve life for some children with severe autism.

  • akerdoc says:

    I have worked as an Emergency Physician for many years, and we have a Psychiatric ER as part of our regular ER. At least 95% of all the patients I take care of with psychotic symptoms in the Psych ER are using marijuana. Several years ago, I did a literature search on this topic, and there are hundreds of articles describing acute psychotic symptoms caused by the use of marijuana.

    I would say close to 100% of the patients I see for drug addiction are also on marijuana.

    We are seeing a large number of patients now with something called marijuana cyclic vomiting syndrome. These people have severe vomiting that is extremely difficult to control. It is extremely difficult to convince the patients that the only way to stop their symptoms is to stop using marijuana. The classic story is someone with severe vomiting who get relief by taking hot baths or showers. Sometimes these people can run their apartment complex out of hot water. Within a few days of stopping the marijuana their symptoms resolve.

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