“Can Marijuana Cause Psychosis?” – (Psychology Today)

Today, I will be commenting on an article (written by Gary Wenk, Ph. D.) on a topic that had become very familiar in the past year or so. That is, the association between marijuana and psychosis. Though the source may initially lead one to assume they know the conclusion of this article (“WEED BAD! BAN NOW!”), it is actually much more nuanced than that. I was pleasantly surprised.

Let’s get right into it.


Given that so many states are now making marijuana available for medical and/or recreational use, the question of whether marijuana causes psychosis is not likely to go away soon. I am often asked by my students the following question: “If I smoke marijuana, will I become psychotic?” The answer depends on three factors: the genes of the person asking the question, the age of the person asking the question, and how much THC is being taken into the body. Let’s consider each condition.


While it’s bothersome that so many of his students seem to word the question in this way (the hysteria is obviously having an effect), I like his honesty so far.


Who are your parents?

Inheriting a genetic predisposition to psychosis makes one vulnerable to the consequences of marijuana. Unfortunately, there are no genetic tests currently available to inform someone with certainty that they are at risk of developing psychosis. Our only option is to consider your siblings: Do any of them seem psychotic to you? If so, then you should seriously reconsider using marijuana.

Despite reports from several high-profile observational studies of a dose-dependent association between cannabis use and risk of psychosis, a causal link between cannabis use and psychotic disorders remains controversial. Why? Observational results are frequently hindered by the possibility that another risk factor associated with cannabis use might be more closely associated with developing psychosis. Alternatively, people who are affected by the early symptoms of schizophrenia might be turning to marijuana to self-medicate themselves. Marijuana use by these nascent psychiatric patients might be reducing some of their symptoms long before they become part of their diagnosis.

A recent study (Molecular Psychiatry 2018, Vol 23, 1287–1292) investigated 10 different genetic variants, called single-nucleotide polymorphisms (SNPs), in almost 80,000 subjects and found an increased risk of schizophrenia if these variants were present in the marijuana users. A word of caution when considering your risk: simply having an SNP that places you at risk is not sufficient to actually induce psychosis, should you decide to use marijuana. Reality is much more complicated than one gene = one disease.


Now, this is interesting.


SNPs occur normally throughout a person’s DNA. They occur almost once in every 1,000 nucleotides on average, which means there are roughly 4 to 5 million SNPs in a pWhile I didn’t have the faintest idea that single nucleotide polymorphisms (SNP’s) existed before now (let alone their purpose). Speaking of which:erson’s genome. These variations may be unique or occur in many individuals; scientists have found more than 100 million SNPs in populations around the world. Most commonly, these variations are found in the DNA between genes. They can act as biological markers, helping scientists locate genes that are associated with disease. When SNPs occur within a gene or in a regulatory region near a gene, they may play a more direct role in disease by affecting the gene’s function.

Most SNPs have no effect on health or development. Some of these genetic differences, however, have proven to be very important in the study of human health. Researchers have found SNPs that may help predict an individual’s response to certain drugs, susceptibility to environmental factors such as toxins, and risk of developing particular diseases. SNPs can also be used to track the inheritance of disease genes within families. Future studies will work to identify SNPs associated with complex diseases such as heart disease, diabetes, and cancer.



This would seem to serve as a good way of determining whether or not marijuana may be a bad choice for a person. While I am inclined to question how THC dosages apply (not all marijuana or marijuana derivatives are equal, particularly in the legal market), that may be considered later.

Let’s read on.


The connection between marijuana and schizophrenia is also muddied by the fact that cannabis use is strongly associated with tobacco consumption. Conversely, tobacco use is strongly correlated with marijuana. Indeed, tobacco may act synergistically with marijuana to create addiction. Making matters worse, tobacco use may increase the risk of becoming schizophrenic (we do not read as much about this in the popular press). 

Taken together, current genetic evidence indicates that the association between marijuana and psychosis may be significantly influenced by tobacco use. This association complicates any direct genetic link between marijuana use and schizophrenia. Thus, marijuana users who also smoke cigarettes face a challenging dilemma: Do they feel genetically lucky?


This is certainly new to me. I have in the past, come across research indicating that substances like alcohol and nicotine act (or CAN act) as sort of magnifiers of the effects of other drugs (one of them being THC). A better word to use may be primer (as opposed to magnifier).

In my previous (linked) post, it was indicated that THC may be linked to alcohol use disorder due to a  priming effect on the brain. It makes me wonder if the connection between marijuana, nicotine and schizophrenia may have similar origins.

It’s a concerning hypothesis. From the standpoint of marijuana use in most localities before it was legal, smoking cigarettes almost always went hand in hand with cannabis use.
While I am relying mainly on the anecdotes of my personal experiences to make this claim, it fits the overall cohorts we’re dealing with. Smoking is generally the first rung on the ladder of destructive gateway substances, with alcohol and marijuana following (though it depends who you ask).

Whatever the case, it’s worth knowing your family’s psychiatric history.

How old are you? Why age matters

Still in the womb? The prenatal brain is very vulnerable to the presence of cannabis.

You’re an adolescent? The available evidence indicates that the adolescent brain is still vulnerable to exogenous cannabinoids. Essentially, cannabis alters the normal trajectory of brain maturation, although the consequences are less severe than those seen following prenatal exposure. The combined evidence from numerous human and animal studies suggests that exposure to cannabis during adolescence has the potential to produce subtle, but lasting, alterations in brain function and behavior. The severity differs according to the duration of use, age at first use, and underlying genetic vulnerabilities that are more likely to appear during adolescence, such as various psychopathologies.

If you’re beyond middle age, the use of whole plant medical cannabis does not have a negative impact on cognition in older patients. Why are the effects of cannabis age-dependent? The answer to this question remains unknown but there is one fascinating potential mechanism that involves what is happening to the stem cells in your brain. Stem cells undergo neurogenesis and give birth to new neurons every day. Neurogenesis is obviously critical for the developing brain from prenatal to adolescence. Neurogenesis begins to decline around middle age and is nearly absent by the time you are ready to retire. 


First of all, the term psychopathologies seems to be psychologist speak for various mental illness traits. It sounds kind of like psychopathy, but it’s not. If memory serves, psychopathy generally starts showing up long before adolescence.

And just so I am clear to my readers:

Note: If you are under the age of majority where you live, leave the intoxicating experiences until you are legal age!

I have to wonder how much of this research is tied up with our evolving knowledge of the endocannabinoid system. As for the rest of this, it makes sense. Prenatal brains are vulnerable to all matter of toxicology, to begin with, though use in teenagers is seemingly less drastic than most PSA material would otherwise have one believe.

Like this article that I happened across just today, for example:

States that legalize recreational marijuana use, and in some cases allow retail sales of the drug, may see more suicide attempts and other self-harm among younger men, a new Stanford Medicine study suggests.

Researchers examined whether rates of self harm injuries — which include suicide attempts and non-suicidal behaviors like cutting — correlate with changing marijuana laws and found an increase among men younger than 40 in states that allow recreational use. The study indicated no such correlation with states that allow only medical marijuana use.

. . .

In certain states, including California, he said, this allows the opening of for-profit dispensaries that sell unregulated varieties of strains and dosages of the drug. The study showed that in states that legalized recreational marijuana use and have robust retail operations, there was an associated 46% increase in self-harm injuries among 21- to 39-year-old men.

“Some states permit only small amounts of homegrown cannabis plants for medical use,” the study reads. “Others have extensive commercialization, permitting multi-billion dollar, competitive retail markets based on systems of dispensaries offering diverse, high-potency products to anyone aged 21 years or older.”

Regular and heavy use of increasingly high potency cannabis products have been linked to risk factors for self-harm and assault injury, the study said, including impaired cognitive function, associated alcohol use, psychosis, depressive disorders, and suicidal ideation and attempts.

“The medical cannabis laws showed no adverse effect on self-harm or assault in the study,” Humphreys said. “But as you move into the more recreational, commercial uses, some results were worrying.”

. . .

“This is particularly disturbing because the human brain is much more plastic in adolescence,” Humphreys said. “Heavy use during adolescent years may do significant damage.”

Pot commercialization tied to self-harm by younger men, study suggests

I like Keith Humphrey’s use of the word may in this article. A seeming acknowledgment of the lack of study in the area of marijuana and marijuana derivatives. Despite this:


Humphreys, who worked as senior policy adviser for the White House Office of National Drug Control Policy from 2009-2010 under the Obama administration, said that there is little research available on the health effects of the legalization of the recreational use of marijuana.

While I am not totally clear on what the role of a senior policy advisor is, it seems reasonable to assume that part of the job is promoting and organizing research in terms of the topic of which you are to be advising policy. Or to put it another way, if the Obama administration was to allow many states to legalize marijuana (FINALLY! Don’t get me wrong), then it might be incredibly helpful to tear down the federally mandated wall between researchers and Non-ATF grown cannabis plants.

Though Humphrey’s sins within the Obama administration’s Office of National Drug Control Policy are not as glaring as Kevin Sabet’s, it still makes me ask . . . what is the point of you?

His boss may have dropped the ball on the opioid crisis (in my opinion, anyway), but Humphreys still seemingly left marijuana users (which he now apparently cares about!) in the lurch by not attempting to break down the research barrier. Or am I wrong? 

Comment below.


Numerous PET imaging studies of humans suggest that the decline in neurogenesis is due to increased levels of brain inflammation that occurs naturally with advancing age. The decline in neurogenesis likely underlies age-related impairments in learning and memory and an increased incidence of depression. Research in my laboratory has demonstrated that a daily low dose of cannabis can significantly reduce brain inflammation. My lab’s research also demonstrated that stimulating cannabis receptors on surviving stem cells can restore neurogenesis. If you would like to read more about this topic, click here.


Here, I find myself annoyed that the CLICK HERE above has been linked to an Amazon listing of a book written by the article’s author (I was expecting a scientific paper).  Though it comes off as mildly similar to the actions of unethical Doctors I have come across in the past, we all need to put food on the table.

Given the number of schools and faculties that I see Dr. Wenk listed under, I feel comfortable that his character is clean. The amount of slime that exists in the online medical space (in particular, in the for-profit alternative medical space aimed at seniors) is ridiculous, so I always approach this stuff from a zero-trust perspective.

But I almost missed the good news of the previous paragraph . . . marijuana could help with the process of ageing. Or should I say, at least help to make the process more bearable. A definite plus in my book.


How much do you smoke every day, and what are you smoking?

The marijuana available today contains far higher concentrations of THC than ever before. Most of the available epidemiological data become moot when we try to compare data collected during the past few decades. Dose matters. How often someone uses marijuana each day also matters. Some of the original studies on the connection between marijuana and psychosis found that heavy users were more likely to develop symptoms of psychosis. Some of these “heavy users” reported smoking over one hundred marijuana cigarettes every day. This is obviously not typical of most users. The problem is that the actual dose consumed is often difficult, or impossible, to determine in epidemiological studies. This is why most epidemiological studies are inconclusive about this topic.


This is certainly a peek behind the curtain for me. Though I’ve known a few quote-heavy users of weed in my time, I don’t see any of them smoking THAT much pot in a day (100 reefers). For one thing, most people I know/knew didn’t have the time. And far more importantly, no one I know/knew would have had the money.

Heavy user . . . more like the Kurt Cobain category for Cannabis!


Today, medical science lacks sufficient data to make a definitive claim regarding whether smoking marijuana induces psychosis. If you’re young, consume a lot of high-dose marijuana products every day, and possess a genetic predisposition to psychosis, then yes, you are at risk. If you’re middle age, occasionally consume marijuana, and carry no known genetic predispositions, then no, you are not at risk. That last condition, your genetics, is the wild card in your genetic deck since science still lacks the ability to define the genetics of psychosis. In spite of the lack of certainty, it is very likely that many people will go ahead and spin the wheel of genetic roulette.


Thus concludes this informative and enlightening article. While it conveys a wise word of caution, it also conveys a hopeful sentiment I’ve yet to find in another expert anywhere near either the Medical or Social Services fields proclaim.

Will future research eventually make it possible to know if high levels of psychoactive substances (such as THC) are likely to cause mental illness in a person? Could this same research also begin to highlight other genetic predispositions? Could this be available to parents at birth?


Will it be eventually possible to tailor psychoactive in such a way that they are safeguarded from triggering these side effects in per-disposed individuals?  

Though this is a much more complex area of research than the knowledgeable prevention enabled by the previous area, I know that some teams are looking at the subject (having come across it in a previous post).

So . . .hopefully?

One thing is for sure . . . the time to legalize is NOW. While it would have been nice to have a well-rounded and explored backlog of research to base the process on, every past administration and world government since Nixon has dropped the ball on the issue (including Obama!). That we are playing catch-up on account of their past idiocy is unfortunate. But as the Zoomers like to say, it is what it is.

Let’s make this right.

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