Cannabis & Psychosis: What Do We Know?

Alternaleaf Team
Written by
Alternaleaf Team
Aug 11, 2023
Last updated:
Dec 15, 2023

Medical cannabis became legal in 2016 in Australia and there are many encouraging  studies and anecdotal evidence that suggest it may help manage a wide variety of conditions. But like any medication, medical cannabis is not without risks. The link between cannabis and psychosis in particular is heavily debated, especially now that cannabis is becoming legalised and accepted in more and more parts of the world.

It can be difficult to determine the risks when there is so much conflicting information about medical cannabis and psychosis. Psychosis is a complex condition and may be a symptom of an underlying disorder or it may occur on its own. Research suggests that cannabis use can put you at risk of experiencing psychosis, but how severe is the risk, and how can you make sure you stay safe?

What is Psychosis?

Psychosis is an altered state of mind that can be a symptom of another condition such as schizophrenia, or it can occur on its own. Psychosis can be caused by illicit drug use, which is referred to as substance-induced psychotic disorder. It can also occur after administration of a prescribed medication, which is known as prescription-drug induced psychosis.

According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), someone having a psychotic episode will experience one or more of the following:

  • Delusions: when someone believes something and won’t be convinced otherwise even when there’s strong evidence that their belief is untrue.
  • Hallucinations: when a person sees, hears, smells, tastes or feels something that  doesn’t exist.
  • Disorganised thinking: if someone’s speech is very difficult to understand, if they tend to switch topics a lot, or their responses to questions aren’t logical it might be a sign of disorganised thinking.  
  • Abnormal motor behaviour: when someone acts in a very strange way, such as unpredictable agitation, excessive  “silliness,” catatonia or repeated actions such as constant grimacing.
  • Negative symptoms: this refers to several symptoms that can cause someone to appear closed off or shut down emotionally and physically, such as reduced movement, avoiding social and work activities and showing a lack of interest in positive experiences.

It’s important to note that cannabis and some other drugs can cause temporary symptoms of psychosis such as hallucinations and disorganised thinking. Usually these symptoms fade as the drug’s effects wear off, but if they are intense enough to require medical attention it may be diagnosed as a substance-induced psychotic disorder.

How Does Medical Cannabis Relate to Psychosis?

It’s difficult to pin down the exact relationship between cannabis and psychosis. The accepted thinking is that there is a connection between the two, however some research suggests the link is overblown or can be explained by other factors. The reason it’s so complicated is that there are often several confounding factors to consider when we talk about cannabis and psychosis, such as other drug use, how heavy and frequent a person’s cannabis use is, pre-existing mental health concerns and age.  

A 2019 analysis by The Lancet, while generally supporting a link between heavy cannabis use and psychosis, also cited a study that found that those who were genetically more likely to use cannabis were also more likely to experience psychosis regardless of their substance use. This raises a question – does cannabis itself cause psychosis or can it cause an inevitable psychotic episode to happen sooner?

A 2023 study on 344 people who were at clinical high risk for psychosis found no correlation between cannabis use and developing psychosis. The study states that in a high risk population, some people may stop using cannabis once they begin noticing psychotic symptoms and suggests that stopping your medical cannabis use is beneficial if you begin to notice any psychotic symptoms.

However, the researchers acknowledge that these findings are at odds with the vast majority of studies that have found links between cannabis and psychosis. So how much evidence is there for the connection?

What are the Links Between Medical Cannabis and Psychosis?

There is a significant body of research that suggests cannabis may cause or worsen psychosis. A study from 2017 followed people who had experienced cannabis-induced psychosis, and found that the rate of people who developed schizophrenia or bipolar disorder after this was 47.4%.

The study also found a connection between younger men and developing psychosis, with the highest risk group being men between 16-25 years. A different study from 2019 found daily cannabis use to be associated with a higher risk of developing a psychotic disorder compared with people who never used cannabis. They also found that the odds of developing a psychotic disorder were nearly five times higher for those who used high-potency cannabis daily.  

These studies suggest that people who experience any psychotic symptoms while using cannabis may want to reduce or avoid cannabis entirely to lower their risk of developing psychotic disorders such as schizophrenia. This is especially true of high-THC cannabis, which may put you at a higher risk of psychosis than lower potency cannabis strains or products.  

How Does Medical Cannabis Affect the Brain?

The exact method by which THC’s effect on the brain may be involved in psychosis isn’t fully understood. We do know that current research suggests that THC’s effect on the endocannabinoid system may cause a disruption to emotional processes, executive function and reward function.

This disruption can mean that the brain might release excessive dopamine or alter levels of certain neurotransmitters that are involved in mood and information processing. These brain chemistry alterations may potentially lead to psychosis in vulnerable people.

Can People at Risk of Psychosis Use Medical Cannabis Safely?

People who have a history of psychosis or are at risk of psychosis should avoid any mind-altering substances, including medical cannabis.

That being said, isolate CBD oil may be safe to use for people at risk of psychosis. Since THC is the psychoactive compound in cannabis, isolate CBD oil doesn’t pose the same risk of psychosis that THC products may.  

CBD may even have some anti-psychotic properties. A randomised controlled trial from 2017 showed that patients with schizophrenia demonstrated reduced psychotic symptoms after being administered CBD oil. But more research is required before it can be said  with certainty that isolate CBD oil is safe for people at risk of psychosis.

As it currently stands, medical cannabis clinics generally won’t prescribe to people with a family history of psychosis, including CBD isolate products. This may change with further research into CBD’s potential in helping manage psychosis.

Can You Recover From Cannabis-Induced Psychotic Disorder?

Before we discuss how likely someone is to recover from cannabis-induced psychotic disorder, it’s important to clarify the difference between cannabis intoxication and cannabis-induced psychotic disorder.

A crucial difference between cannabis-induced psychotic disorder and cannabis intoxication is that a person experiencing cannabis-induced psychotic disorder will typically forget that a drug is causing their psychotic symptoms. They may instead believe that their hallucinations or delusions are real. This is referred to as lacking “insight” into how the brain is being affected by a psychoactive substance.

Thankfully, cannabis-induced psychotic disorder can often be treated and recovered from relatively quickly. But this depends on the severity of a person’s psychotic symptoms, the amount and potency of cannabis used, and other factors such as their environment and support network.

If someone experiencing cannabis-induced psychotic disorder completely stops using cannabis and immediately seeks medical support they may make a full recovery. Of course, someone in a state of psychosis is unlikely to seek help themselves, so it’s crucial to educate people and give support to those who may be at risk of experiencing psychosis.  

The DSM-5 also explains that if someone is predisposed to a psychotic disorder such as schizophrenia and using cannabis causes the disorder to develop, a full recovery may not be possible. Schizophrenia and some other psychotic disorders are chronic conditions and often need life-long treatment.

Harm Reduction When Using Medical Cannabis

The average THC levels in cannabis worldwide have been significantly increasing over the years, which may be a factor in the possible increase in people experiencing psychosis related to cannabis use. Using lower potency cannabis, or even CBD-isolate medical cannabis products might be one way to reduce the risk of experiencing psychosis.

Another way to reduce the risk of experiencing cannabis-induced psychosis is to only consume medical cannabis according to your prescribed dosage. Some studies have shown a possible increased chance of experiencing psychosis if you consume cannabis more often. You may rely on using medical cannabis frequently to manage a chronic condition – if this is the case it’s important to speak to your doctor about how you can stay safe while using medical cannabis regularly.  

How Can I Stay Safe While Using Medical Cannabis?

Above all, it’s essential to be aware of the potential risks of medical cannabis use. If you use medical cannabis with a doctor’s guidance and aren’t already at risk of developing psychosis, it's very unlikely that you will experience it. Psychosis is a serious medical concern, so it’s important that you stay informed about whatever medication you’re taking and how it might put you at risk.

If you have a family history of psychosis, are an adolescent or have experienced psychotic symptoms in the past, medical cannabis won’t be the right fit. Be sure to discuss this with a doctor who can help you find an alternate treatment that’s safe for you.

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