Healthcare (Commonwealth Union) – Fresh research from King’s College London’s Institute of Psychiatry, Psychology & Neuroscience (IoPPN), in collaboration with the University of Bath, has revealed that the motivation behind someone’s decision to use cannabis can play a major role in raising their likelihood of experiencing paranoia.
Globally, both the strength and use of cannabis are on the rise, with dependence and cannabis-related psychosis also climbing, particularly in North America. Drawing on data from Cannabis & Me—the largest survey of its kind—two new studies have pinpointed specific risk factors linked to more severe forms of paranoia among cannabis consumers.
The first paper, released today in BMJ Mental Health, investigated how an individual’s initial reasons for trying cannabis influenced their later patterns of use.
A total of 3,389 past and current users aged 18 and over took part in a survey that assessed their motivations for starting and continuing cannabis use, their weekly intake measured in THC units, and their overall mental health.
The findings highlighted a clear trend: people who began using cannabis to manage medical or psychological issues—such as pain, anxiety, depression, or early psychotic symptoms—showed significantly higher paranoia scores.
By contrast, those who experimented with cannabis out of curiosity, recreation, or social influence recorded the lowest average levels of paranoia and anxiety.
Dr Edoardo Spinazzola, Research Assistant at King’s IoPPN and lead author of the study, explained that their findings indicate that people who turn to cannabis as a way of coping with physical or psychological distress may experience heightened levels of paranoia, anxiety, and depression. In fact, many of these groups recorded average anxiety and depression scores that exceeded the threshold typically used to recommend counselling.
Participants were also asked about how often they used cannabis and the potency of the products they consumed. This allowed the researchers to calculate their average weekly intake of Tetrahydrocannabinol (THC) – the main psychoactive ingredient in cannabis.
On average, respondents consumed 206 THC units per week. Based on an estimated THC content of 20 per cent, which is common in the cannabis available in London, this equates to around 10–17 joints weekly.
But among those who began using cannabis specifically to ease anxiety or depression, or who first tried it because others in their household were already users, the average weekly consumption was noticeably higher at 248, 254.7, and 286.9 THC units respectively.
Professor Tom Freeman, Director of the Addiction and Mental Health Group at the University of Bath and an author of the study says “A key finding of our study is that people who first used cannabis to manage anxiety or depression, or because a family member was using it, showed higher levels of cannabis use overall.
“In future, standard THC units could be used in a similar way to alcohol units – for example, to help people to track their cannabis consumption and better manage its effects on their health.”
In a separate paper published in Psychological Medicine, scientists examined how childhood trauma, paranoia, and cannabis use are interconnected.
The team drew on the same Cannabis & Me survey data, where just over half of participants (52%) reported having experienced some type of trauma.
Their analysis showed that individuals who went through childhood trauma tended to have higher average levels of paranoia than those without such experiences, with emotional and physical abuse being the strongest predictors.
Ultimately, the researchers found that cannabis use intensifies the connection between childhood trauma and paranoia, though the effect differs depending on the type of trauma. People who reported emotional abuse or conflict within the home showed the clearest link to both increased THC use and paranoia scores. In contrast, participants who had experienced bullying, sexual abuse, physical abuse, or neglect (both physical and emotional) did not display the same pattern.
