Using cannabis to cope with anxiety or depression? You may be at higher risk of paranoia, study says

People who start using cannabis to cope with physical or mental health problems are more likely to experience severe paranoia, a new study has found.

Many of these people also report depression and anxiety symptoms at levels that would normally see them referred to counselling, according to the study, which was published in the BMJ Mental Health journal.

The findings indicate “the reason someone first starts using cannabis can dramatically impact their long-term health,” Dr Edoardo Spinazzola, one of the study’s authors and a researcher studying the link between cannabis and psychosis at King’s College London, said in a statement.

Spinazzola’s team tracked nearly 3,400 UK adults’ average weekly consumption of delta-9-tetrahydrocannabinol (THC), which is the main psychoactive compound in cannabis that makes people feel “high”.

The average respondent consumed 206 units of THC per week, equivalent to roughly 10 to 17 “joints,” the researchers said. But that level was much higher among people who started using cannabis to help manage anxiety or depression, to about 248 and 255 units, respectively.

People who used cannabis to self-medicate also reported more paranoia symptoms than people who tried the drug for fun, curiosity, or with their friends.

The findings are the latest to connect cannabis use to poor mental health.

In another recent study using the same dataset, researchers found that people who had experienced physical or emotional abuse as children were more likely to be paranoid as adults – and that cannabis use made that link stronger.

There is “a clear association between trauma and future paranoia,” Dr Giulia Trotta, a psychiatrist and researcher at King’s College London who worked on the study, said in a statement.

The findings indicate “cannabis use can further exacerbate the effects of this, depending on what form the trauma takes,” Trotta added.

Earlier this week, a separate study in the United States found that using highly potent cannabis products – such as edibles or concentrates for vapes – raises the risk of serious mental health conditions such as psychosis, schizophrenia, and addiction.

The researchers behind the latest study said that doctors should ask their patients why they started using cannabis as a way to identify whether they could benefit from additional support. That could help prevent people from sliding into “potentially disabling” paranoia or mental health problems, they said.

Dr Emily Finch, chair of the UK’s Royal College of Psychiatrists’ Addiction Faculty, said the findings underscore that “cannabis can have significant adverse effects on users’ mental health”. 

“Society must be more aware of the substantial evidence on cannabis harms, and correct the widespread misapprehension that cannabis is not an addictive substance,” Finch, who was not involved with the study, said in a statement.