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Schizophrenia and Marijuana: Does Cannabis Use Cause Teen Schizophrenia?

Cannabis use has been shown to increase the likelihood that adolescents will develop schizophrenia or bipolar disorder, particularly if they have other risk factors. Research suggests that THC, the active ingredient in marijuana, can cause temporary psychotic symptoms, which may increase the risk of developing a mental health disorder.

About a third of teens who use cannabis report experiencing hallucinations or paranoia—which significantly increases their risk of developing schizophrenia or bipolar disorder. Explore the latest research from Newport Healthcare.

Is There a Link Between Teen Marijuana Use and Schizophrenia?

Given the widespread legalization of marijuana in the United States, and the increased acceptance of the drug as a result, experts are continuing to examine the connection. And the research suggests a clear association, particularly when adolescents are already at risk for the disorder.

Specifically, studies show that people who use marijuana are more likely to develop temporary cannabis-induced psychosis, with symptoms like hallucinations, paranoia, and detachment from reality. In addition, teens who use marijuana appear to be at increased risk for serious mental illnesses, including schizophrenia and bipolar disorder. Let’s take a closer look at the research.

How Many Teens Use Marijuana?

This issue of cannabis and psychosis is garnering attention due to the high number of teenagers who use weed. According to the CDC’s most recent research on teen marijuana use, 16% of high school students use marijuana regularly. In addition to vaping or smoking marijuana, teens and young adults also consume marijuana edibles, which are easier to get than ever before due to widespread marijuana legalization.

Increased use and higher potency of marijuana is leading to higher rates of cannabis-induced psychosis in adolescents. About a third of teens (ages 14–18) who use cannabis report experiencing hallucinations or paranoia. In general, the overall increase in cannabis use is leading to more psychotic disorders and other cannabis-induced mental health disorders. A new study conducted by the healthcare-analytics company Truveta shows that diagnoses for cannabis-induced disorders were more than 50% higher in 2023 than in 2019.

Does Smoking Weed Cause Schizophrenia? 

Researchers are looking at a number of questions related to the cannabis-schizophrenia link. Firstly, does cannabis use cause an increased risk of this mental illness? Second, can teen cannabis use trigger schizophrenia symptoms in an apparently healthy adolescent? Let’s look at some of the studies on the link between THC and schizophrenia, and whether cannabis can cause a psychotic disorder.

A large body of research suggests that THC, the active ingredient in marijuana, can cause temporary psychotic symptoms. (CBD, which is not psychoactive, and THC, are two of the primary chemicals in marijuana.) As far as the link between marijuana and schizophrenia, many researchers believe that cannabis use may be what’s known as a “component cause.”

In other words, marijuana use can cause teen schizophrenia if the adolescent is already at risk for the disorder. Moreover, the likelihood of marijuana causing schizophrenia or psychosis seems to depend on various criteria. These include the strength of the drug, how often a teen uses marijuana, and how long they use it over time.

In addition, experiencing symptoms of psychosis after using marijuana increases the risk of developing a mental health disorder. According to a study in the American Journal of Psychiatry, individuals who have even one psychotic episode following cannabis use have a 47% higher chance of developing schizophrenia or bipolar disorder. And adolescents and young adults are at the highest risk.

Additional Marijuana and Schizophrenia Research Findings

Additional research strengthens the body of evidence supporting the weed-schizophrenia link. According to a 2021 study in Denmark, the proportion of people who develop schizophrenia associated with cannabis use disorder has increased by 3-4 times during the past two decades. In 1995, 2% of schizophrenia diagnoses in the country were associated with cannabis use disorder. In 2000, it increased to around 4%. Since 2010, that figure has increased to 8%. The researchers attribute this increase to the rise in the use and potency of marijuana.

2018 study published in the Journal of Molecular Psychiatry also examined the association between marijuana and schizophrenia. This study clearly found that the cannabis-schizophrenia relationship is causal and suggested that this evidence should inform policies and public health messaging about weed use, especially in reference to its potential mental health consequences.

In fact, another study on cannabis and schizophrenia found that cannabis use doubles the risk of developing psychosis in vulnerable people. Moreover, it showed a relationship between the onset of schizophrenia and the age when a person first starts using marijuana—the younger the smoker, the higher the risk.

"Our research demonstrates that cannabis has a differential risk on susceptible versus non-susceptible individuals. In other words, young people with a genetic susceptibility to schizophrenia - those who have psychiatric disorders in their families - should bear in mind that they're playing with fire if they smoke pot during adolescence."

- Dr. Ron Barzilary, Tel Aviv University's Sackler School of Medicine.

Smoking Weed with Schizophrenia 

The question, “Does smoking weed cause schizophrenia?” is a nuanced one. However, the statistics are clear on another correlation between schizophrenia and marijuana: People with schizophrenia or with a genetic predisposition to schizophrenia are more likely to start using marijuana, use it more regularly, and consume more of it over their lifetime.

Published in the journal Nature Neuroscience, a recent marijuana and schizophrenia research study used genetic data from the DNA ancestry database 23andMe. Researchers found a significant genetic correlation that indicates a higher probability of cannabis use by people with schizophrenia or emerging schizophrenia symptoms.

What Are the Symptoms of Schizophrenia?

It’s important to be familiar with the mental health disorder called schizophrenia and the psychotic symptoms that accompany this mental illness. The word schizophrenia has its roots in German and roughly translates as “a splitting of the mind.” People with schizophrenia have trouble processing emotions. They may have delusions, hallucinations, or disorganized speech. At times they may be completely detached from reality. Cannabis-induced psychosis can produce many of these symptoms.

Furthermore, schizophrenia behaviors usually begin to develop in adolescence or young adulthood. According to the National Institute of Mental Health, symptoms of schizophrenia often start when people are under age 30. Learning more about the disease, and how it can be detected, may help parents provide needed care to their teens with schizophrenia.

Early Signs of Schizophrenia 

If an adolescent does not have a genetic susceptibility to the disorder, teen cannabis use is not likely to lead to the onset of schizophrenia symptoms. However, there is no test for such a genetic susceptibility, and schizophrenia does not necessarily run in families. Therefore, it’s difficult to know whether or not a teenager is susceptible to psychiatric disorders involving psychosis.

However, parents can watch for warning signs. Most people with schizophrenia receive their schizophrenia diagnosis in adolescence or young adulthood. Moreover, onset is usually earlier in men than in women. Early symptoms may include the following:

  • Depression

  • Withdrawing from relationships and social activities

  • Trouble expressing emotion appropriately

  • Insomnia or sleeping too much

  • Talking in strange or irrational ways

  • Forgetfulness and inability to concentrate

  • Acting suspicious or hostile

  • Decline in personal hygiene.

These warning signs indicate that a teen or young adult should have a professional mental health assessment. A mental health professional can determine whether a teen meets the criteria for a schizophrenia diagnosis. Treating schizophrenia is typically a multifaceted process involving therapy, medication, and supportive changes in lifestyle and habits.

Consequences of Legalizing Marijuana

While marijuana has been found to have beneficial physical and mental health effects in some cases, for some adults, marijuana and teenagers do not make a healthy mix. Doctors and psychiatrists generally agree that medical marijuana use is not appropriate for teens. As a result, the American Academy of Pediatrics (AAP) warned both doctors and parents that children need protection from the effects of marijuana legalization in the United States.

As the AAP points out, human brain development is ongoing until the mid-20s, and cannabis use is associated with changes in the neurochemical systems in the brain. While these changes reverse in adults when they stop using marijuana, it’s not clear whether that’s also the case for adolescents. Hence, marijuana use by adolescents can result in abnormal brain development and function even if they stop using the drug later on.

The American Academy of Child and Adolescent Psychiatry also made a policy statement on marijuana legalization in 2017, noting that adolescents are especially vulnerable to marijuana’s many known adverse effects. The report stated, “One in six adolescent marijuana users develops cannabis use disorder, a well-characterized syndrome involving tolerance, withdrawal, and continued use despite significant associated impairments.” According to the National Institute on Drug Abuse ("NIDA"), students who use marijuana before age 18 are four to seven times as likely to develop a marijuana use disorder than adults.

Furthermore, NIDA reports that marijuana potency has steadily increased over the past 30 years, further increasing the risk of marijuana addiction. In the early 1990s, the average THC content in confiscated marijuana samples was roughly 3.8%. By 2020, the THC content had risen dramatically, to an average of more than 15% and, in some vaping products, as high as 80%. One of the notable effects of marijuana legalization is a change in teens’ perception of the drug. In the age of legalization, teenagers are growing more tolerant and accepting of marijuana use.

The perceived risk of marijuana use among teens has steeply declined since the mid-2010s. Among 8th graders, less than half of teens perceived any great risk in using marijuana regularly. Only about a third of 10th and 12th graders perceived any great risk in regular marijuana use. In addition, the survey tracked teens’ disapproval of marijuana use, and found that these numbers had also dropped over the last decade, with about two-thirds of high schoolers disapproving of teenage marijuana use.

Moreover, parents’ use of recreational marijuana colors their children’s attitudes. Hence, how parents react to the consequences of marijuana legalization matters. Teenagers and adolescents experience the impact of parental choices profoundly.

"Parents who use marijuana themselves may not fully realize the effect this can have on their children. Seeing parents use marijuana makes kids more likely to use it themselves, whether or not their parents tell them not to, because actions speak louder than words."
- Sheryl A. Ryan, MD, American Academy of Pediatrics Committee on Substance Use and Prevention

Sackler School of Medicine

Education on Schizophrenia and Marijuana Is Essential 

To summarize, marijuana does not in itself cause a teen to develop schizophrenia. But research on THC and schizophrenia strongly suggests that cannabis can trigger psychotic symptoms when an individual is already predisposed to the disorder.

Therefore, parents should protect their children by educating them thoroughly about the link between schizophrenia and marijuana and becoming educated themselves. Both parents and teens should understand the schizophrenia-weed link and the potential for experiencing drug-induced psychosis.

Moreover, it’s not just the THC and schizophrenia association that is concerning. The American Psychiatric Association states that cannabis may also exacerbate or trigger the start of other mental health issues, particularly in young people. And for teens with depression, cannabis use can create an increased risk of suicidal ideation and attempts. 

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