New research from King’s College London (KCL) and the University of Bath shows that cannabis users can be more susceptible to paranoia.
In 2022, KCL launched the largest study into causes, patterns, and effects of cannabis use – Cannabis&Me – headed by Dr Marta Di Forti and funded by the Medical Research Council.
The online survey consisted of almost 5000 participants, cross-referencing a questionnaire on childhood trauma with the Green et al. Paranoid Thoughts Scale (developed in 2007, and widely used to assess paranoid thinking in patients).
Cannabis is the most widely used drug in England and Wales, with 14% of 16- to 24-year-olds using.
The average user consumes 206 units of Tetrahydrocannabinol (THC – the psychoactive chemical in cannabis) per week. Meanwhile, those who use it to self-medicate for anxiety, depression, or because people in the household use it use an average of 248 to 287 units of THC per week.
Two papers published in August 2025 show that the Cannabis&Me study has proven that “Childhood trauma was strongly associated with paranoia” and “Cannabis use significantly predicted paranoia”.
The paper published by BMJ Mental Health concluded, “Initiating cannabis use for self-medication is associated with higher average THC consumption, and increased anxiety, depression and paranoia.”
The negative effects of self-medicating with cannabis due to physical or mental health were prevalent in the results of the study. Self-medicating users show higher weekly consumption, heightened paranoia, and increased symptoms of anxiety and depression.
One-in-five people in the UK suffer from paranoia at some point in their lives
