3 Studies That Prove Cannabis Does Not Cause Psychosis

One of the biggest myths about cannabis is that it causes psychosis. 

It is regularly touted in mainstream press and by prohibitionists as one of the main reasons why weed should remain illegal. 

What these views fail to realise, however, is that the association between cannabis use and psychosis is not causative. 

In fact, there are a number of recent studies that prove conclusively that cannabis doesn’t cause psychosis. Here they are:

1. Twin study

This study from 2021 on twins found that THC use has little impact on rates of psychosis. Looking at nearly 3,000 sets of twins over their lifetime, researchers found no evidence of an effect of cannabis on psychosis rates. 

Put simply, rates of psychosis were the same no matter that one twin used cannabis and the other didn’t. 

“Although cannabis use and disorder are consistently associated with increased risk of psychosis,” the authors write, “the present results suggest this association is likely attributable to familial confounds rather than a causal effect of cannabis exposure.”

2. Schizophrenia study

Published in 2018, this study looked at the genome of nearly 200,000 people and found that those who are genetically predisposed to schizophrenia are more likely to smoke weed, possibly as a form of self-medication.

“Previous studies have often shown that cannabis use and schizophrenia are associated with each other. However, we also studied whether this association is causal,” said Jacqueline Vink, lead author of the study.

“Our study showed that people with a vulnerability to develop schizophrenia are at increased risk of using cannabis.”

3. Review study

In Cannabis and Psychosis: a Critical Overview of the Relationship, researchers looked at recent research on cannabis and psychosis, including studies done with schizophrenic patients and studies of first-episode psychosis.

They found that the evidence suggests that cannabis does not in itself cause a psychosis disorder.

“Rather, the evidence leads us to conclude that both early use and heavy use of cannabis are more likely in individuals with a vulnerability to psychosis,” the study says. 

“Future research studies that focus exclusively on the cannabis-psychosis association will therefore be of little value in our quest to better understand psychosis and how and why it occurs.”

‘Skunk’ is a media buzzword 

If you read the British tabloids, you might read about ‘Skunk’, a super-potent and highly addictive type of cannabis. In reality, however, skunk is just high-THC cannabis – you know, like the high-THC cannabis being prescribed by doctors in the UK and around the world. 

Before the word was hijacked by fear-mongering journalists, skunk (or Skunk #1) was actually the name of a certain cultivar (or strain) of cannabis – no different to hundreds of other strains that have been developed around the world. 

It was given its name due to its pungent smell, which resembles that produced by a skunk, just as Lemon Haze, another strain with high levels of THC, was named due to its citrusy stench. 

Cannabis risks

Now, just because cannabis use does not cause psychosis does not mean there aren’t risks involved with its use, especially when you’re young and your brain is still developing. 

Chronic, high doses of THC – particularly during adolescence – can affect the way the brain develops. In people already at risk of mental disorders such as psychosis, it may bring on symptoms sooner or make them worse. 

However, healthy adults have little increased risk of mental health issues. This is displayed by the fact that while cannabis use has increased in many populations, including the UK, the corresponding level of psychosis incidence has not.

Additionally, rates of cannabis addiction are low (around 10% of consumers, which is below average compared to other drugs) and can be massively reduced further with the concurrent use of CBD, safe methods of consumption, and mindful use. This book and this course can also help. 


For whatever reason, some politicians and mainstream media outlets in the UK refuse to give up the notion that cannabis causes psychosis. 

This is despite the fact that there’s evidence out there showing that this is not the case. 

The truth is, when used responsibly by an adult, cannabis is very, very safe. A lot safer than alcohol, tobacco, caffeine, aspirin, shellfish, peanuts, and even getting in or out the bathtub. 

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