Does High Potency Cannabis Increase the Risk of Psychosis? [Latest Research]

We take a look at the latest evidence


The relationship between cannabis and psychosis has been well-publicized and is often used by anti-marijuana campaigners to highlight the dangers of the herb. Some sources estimate marijuana to be involved in around 50% of all cases of psychosis, schizophrenia, and related mental illnesses.

A recent study has found that the risk of developing psychosis is especially high when users opt for the THC-rich strains which are now becoming more widespread. However, for people using marijuana to deal with conditions such as chronic pain, a generous dose of THC may be the only way to keep their symptoms under control and live a relatively normal life. So, is it possible to enjoy the benefits of cannabis without the risk?

In this article, we look at the complex relationship between marijuana and psychosis, explore the latest research on the subject, and ask what can be done to reduce the risk of developing this serious problem.

The Link Between Cannabis and Psychosis

In recent years, marijuana has received a great deal of attention for its medicinal properties, but historically it was best known for its intoxicating effects. These effects are primarily due to the cannabinoid known as THC, or ∆9-tetrahydrocannabinol to give the compound its full name.

THC has several dramatic physical and psychological effects. It is capable of interacting with our bodies’ endocannabinoid systems, specifically CB1 receptors in the brain. This interaction is what gives cannabis its characteristic high, and is also responsible for many of the herb’s medicinal benefits.

However, too much THC can have a negative impact on the chemistry of the brain. It is thought to cause changes in the prefrontal cortex, the area associated with memory, perception, and cognitive function. THC is also believed to affect the brain’s dopamine system. This is related to the reward response and is involved in phenomena such as cravings and addiction.

Experienced cannabis users will know that high doses of THC can cause unwanted side effects such as anxiety and paranoia. These effects are usually short-lived, but in some cases, they can lead to more serious problems.

The risk of developing cannabis-induced psychosis or schizophrenia is thought to be greatest in younger people whose brains are still developing. In addition to this, a new study has found that using high-THC strains may increase the risk significantly.

The Latest Research on Marijuana and Psychosis

The study in question was published in The Lancet in March 2019. The research was inspired by differences in the incidence of schizophrenia around the world, especially in areas such as South London where the prevalence increased significantly between 1965 and 1999. This led the study authors Marta Di Forti et al. to question whether these differences were due to increased marijuana use and potency.

The researchers gathered data over five years, between 2010 and 2015. The information was collected from 11 different centers located in the UK, France, Italy, Spain, the Netherlands, and Brazil. The participants were aged between 18 and 64 years and had presented to psychiatric services with first-episode psychosis. In addition to the 901 patients involved in the study, a further 1237 healthy people were recruited to act as controls.

The participants were asked to answer questions relating to their lifetime marijuana use and frequency. Marijuana potency was estimated using data for each country provided by the European Monitoring Centre for Drugs and Drug Addiction report conducted in 2016. Cannabis with a THC content below 10% was classed as low-potency, while that with a THC content of 10% or above was classed as high-potency.

What Did the Researchers Find?

The results of the study indicate that there is a clear link between cannabis use, higher THC content, and the risk of developing psychosis. The key findings are as follows:

  • Those who used cannabis were more at risk of psychosis than those who had never tried the herb
  • The odds increased slightly for those who used cannabis daily
  • The odds doubled for those who started using cannabis before the age of 15
  • The odds were almost five times higher for those using high-potency marijuana (>10% THC)
  • If there was no access to high-potency marijuana, an estimated 12% of cases of psychosis could potentially be prevented
  • This figure rose to 30% in London and a stunning 50% in Amsterdam

The study found that almost 65% of the patients in the study had tried cannabis in their lifetime, compared with just 46% of the control subjects. Daily use was reported by 29% of patients compared with just under 7% of the controls, and exposure to high-THC marijuana was 35% and 19% respectively.

Interestingly, exposure to high-THC strains rose dramatically to 51% and 26% in London, where the majority of cannabis is estimated to have a THC content of at least 14%. These figures were even higher in Amsterdam (69% and 54%) where marijuana is famously decriminalized and has been for many years. Perhaps unsurprisingly, these two cities had the highest prevalence of psychosis of all the centers included in the study.

So, it seems that there is a direct correlation between cannabis use, THC content, and psychosis. However, with more and more places now legalizing the herb, it seems that it will only grow in popularity over the coming years.

Therefore, the most important question may not be “does cannabis cause psychosis?” but rather “what can we do to prevent it?”

Reducing the Risk of Cannabis-Induced Psychosis

Like any drug, marijuana carries certain risks, with psychosis being just one of them. However, it also has many potential benefits, and for some people, these far outweigh the hazards. For patients who are suffering from debilitating conditions such as multiple sclerosis or the side effects of chemotherapy, medical cannabis may be the only way to get relief from their symptoms. So, how can these people enjoy the respite provided by weed while reducing their risk of psychosis?

The answer may lie in another cannabis-compound known as CBD (cannabidiol). Unlike THC, CBD does not have intoxicating properties, and it is commonly used in to treat a wide range of medical conditions. CBD is also thought to counteract some of the adverse effects of THC, including psychotic symptoms.

Research has shown that while THC may increase anxiety and psychotic symptoms, CBD appears to have the opposite effect. Furthermore, according to a 2006 study, it seems to be both safe and well-tolerated by people suffering from these conditions.

It is possible to find high CBD/low THC cannabis strains, or purchase CBD in various forms such as oil, capsules, or edibles. By choosing a marijuana strain with a higher CBD to THC ratio, or using CBD alongside your regular weed, you could reduce your chances of developing unwanted side effects.

Although CBD may be helpful, one of the best ways to keep the hazards of cannabis use to a minimum is with better education. In countries such as the UK where the herb is illegal, there is a real lack of information regarding how to use marijuana safely. Perhaps it is time for these governments to accept that people are going to find a way to get high regardless of the law and put policies in place to protect vulnerable people such as teenagers.

Could Legalization Reduce the Risk of Cannabis-Induced Psychosis?

One compelling argument for cannabis legalization is that changes in the law would make it easier for people to educate themselves without the fear of prosecution.

Legalization would also provide more control over the THC content of weed, allowing access to less potent strains for those who want it. As an example, you only need to look at London, one of the areas most severely affected by psychosis. Here cannabis is still illegal and only available on the black market. Therefore, buyers usually have no idea how much THC is in their stash, let alone any choice in the matter.

While legalization will not completely eradicate the problem, it does seem like a step in the right direction. Accepting that people will always find a way to get high and helping them to do so safely seems like the most sensible solution.

Does High Potency Marijuana Increase Psychosis Risk? Final Thoughts

The latest research has highlighted the link between high potency cannabis strains and psychosis. This finding is now more important than ever as marijuana appears to be getting stronger all the time.

It is now not unusual to find strains containing well over 20% THC. This means it is crucial that people wanting to use weed for recreational or medicinal purposes educate themselves about the potential dangers. While using cannabis could lead to psychosis or schizophrenia for some people, it may be possible to minimize the risk as long as you know how.

If you, a friend, or family member is being affected by the issues addressed in this article, we urge you to seek medical attention as soon as possible. Remember, the sooner you ask for help, the sooner you can begin the road to recovery.

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