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

Many of these people also report symptoms of depression and anxiety to a degree that would normally lead to them being referred for psychological help, according to the study published in the journal BMJ Mental Health.

The findings show that "the reason a person starts using cannabis can have a dramatic impact on their long-term health," said Dr. Edoardo Spinazzola, one of the study's authors and a researcher studying the link between cannabis and psychosis at King's College London.

Spinazzola's team tracked the average weekly consumption of delta-9-tetrahydrocannabinol (THC) among nearly 3,400 adults in the UK. THC is the main psychoactive substance in cannabis that makes people feel "high." 

The average respondent consumed 206 units of THC per week, which is equivalent to about 10 to 17 joints, the researchers say. But that level was much higher among people who started using cannabis to cope with anxiety or depression—about 248 and 255 units, respectively.

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

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

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

There is a "clear link between trauma and future paranoia," said Dr. Julia Trotta, a psychiatrist and researcher at King's College London who worked on the study.

The results show that "cannabis use may amplify the effects of this, depending on the form the trauma takes," Trotta added.

Earlier this week, a separate study in the US found that using potent cannabis products — such as edibles or vape concentrates — increases the risk of serious mental illnesses such as psychosis, schizophrenia, and addiction. 

The researchers behind the latest study said doctors should ask their patients why they started using cannabis to determine whether they could benefit from additional support. This could help prevent people from developing "potentially debilitating" paranoia or mental health problems, they said.

Dr. Emily Finch, chair of the Addiction Faculty at the Royal College of Psychiatrists in the United Kingdom, said the findings underscore that "cannabis can have significant adverse effects on the mental health of users."

"The public needs to be more aware of the substantial evidence of the harms of cannabis and to correct the widespread misconception that cannabis is not an addictive substance," Finch added. | BGNES