A new study from King’s College London and the University of Bath has found that people who use cannabis to cope with problems like anxiety, depression, or pain are more likely to experience paranoia.
The research highlights how the reasons behind someone’s first cannabis use can strongly affect their mental health in the long run.
Cannabis use is becoming more common around the world, and the amount of THC—the main chemical that affects the brain—is also increasing. As a result, more people are becoming dependent on it or developing serious mental health issues like psychosis.
Two new studies based on data from a large survey called “Cannabis & Me” looked into why people start using cannabis and how it relates to mental health, especially paranoia.
The first study, published in BMJ Mental Health, asked over 3,300 adults about their cannabis use and mental health. The people who said they first used cannabis to deal with physical or mental problems—such as pain, anxiety, or even early signs of psychosis—had the highest levels of paranoia.
On the other hand, people who first tried cannabis out of curiosity or with friends had the lowest paranoia and anxiety levels.
The researchers also looked at how much cannabis people were using. On average, people in the study consumed 206 units of THC per week.
This is about the same as 10 to 17 joints if the cannabis has a THC level of around 20%, which is typical in London. But people who started using cannabis to manage anxiety or depression used even more—up to 254 units or more per week.
The study suggests that using cannabis to self-treat mental or physical pain may lead to worse mental health outcomes. The researchers say this is important because many people with anxiety or depression might turn to cannabis hoping it will help—but it could actually make things worse.
Professor Tom Freeman, one of the study’s authors, suggested that measuring cannabis in “THC units,” like how we measure alcohol, could help users keep track of their intake and avoid harmful effects.
In the second study, published in Psychological Medicine, the same researchers looked at the connection between childhood trauma, paranoia, and cannabis use. More than half of the people in the survey had experienced some type of trauma when they were young. Those who had been through emotional or physical abuse showed higher levels of paranoia.
People who had suffered emotional abuse or lived in homes with lots of conflict were also more likely to use more cannabis and report more paranoia. Interestingly, the type of trauma mattered.
For example, those who reported bullying, neglect, or physical abuse didn’t show the same connection between cannabis use and paranoia as those who had experienced emotional abuse.
The researchers believe that early trauma can lead to paranoia later in life, and that cannabis can make this worse—especially if people use it to cope with emotional pain. They say doctors should ask about past trauma when treating people with paranoia and cannabis use.
Professor Marta Di Forti, who led both studies, explained that many people use cannabis to deal with emotional and physical pain. But this coping method could be risky and might make mental health worse over time. She also warned that as more countries legalize cannabis, it’s important to have public health education and mental health support in place.
These findings show that cannabis use is not always safe, especially for people with past trauma or mental health challenges. Understanding the reasons behind cannabis use—and the risks that come with it—can help people make safer choices.
The study is published in BMJ Mental Health.
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