Warning over cannabis use as self-medication

The drug is used by some to treat mental health problems

Those who use cannabis to self-medicate are at greater risk of paranoia than recreational users, the largest survey into the drug has found.

The three-year study, published under two reports, was the first to investigate why users decided to start using cannabis and how this reason affected the length of time they took it.

Those who took the drug to treat anxiety, depression or pain reported higher paranoia scores and used the drug for longer than those who tried it for fun.

Senior study author Dr Tom Freeman, from the University of Bath, said: "If somebody's using to self-medicate, this can then lead to a longer-term chronic pattern of use."

A total of 3,389 former and current cannabis users aged 18 and over completed the Cannabis and Me survey as part of the study.

The first study report revealed that, on average, users consumed 10 to 17 joints per week or 206 units of tetrahydrocannabinol (THC), the main psychoactive compound in cannabis.

It found that those who began using the drug to cope with anxiety, depression, or because others in their household were already using it, consumed significantly higher weekly amounts.

The second study report focused on the relationship between childhood trauma, paranoia and cannabis use.

More than half of the respondents reported experiencing some form of trauma, the research found.

Dr Tom Freeman said self-medicating cannabis users were likely to use for longer

Dr Freeman said: "It is the first UK study to look at specific cannabis use, with very detailed measures of cannabis use, and also its health effects on people who use.

"Those people who use cannabis for more social, recreational purposes tended to have fewer problems and use less cannabis in the long term.

"What we found was that people who use cannabis to manage mental health problems, such as anxiety and depression, or because family members were using it, they had a higher level of cannabis use and greater risk."

The Cannabis and Me study was funded by the Medical Research Council and jointly led by the University of Bath and King's College London.