For people who are addicted to cannabis, one treatment option may be, paradoxically, to take pills containing an extract of cannabis.
The first test of the idea has found that people taking capsules of this extract, known as cannabidiol or CBD, nearly halved the amount of cannabis they smoked, according to results presented at New Scientist Live this week.
Cannabis is usually seen as a soft drug, but some users – about 1 in 10 by one estimate – become addicted, getting withdrawal symptoms such as anxiety and insomnia when they try to stop.
The number of people seeking treatment because they can’t quit smoking cannabis has been rising in the past decade, linked with a use of the more potent form known as skunk, said Val Curran of University College London at the event.
The two main psychoactive substances in cannabis are CBD and THC, the compound responsible for the high. While THC tends to increase anxiety, CBD makes people calmer. “CBD gets rid of the toxic effects of THC,” said Curran.
Her team has been running a trial, where people undertook a four-week course of CBD to alleviate withdrawal symptoms to help them quit smoking cannabis. It involved 82 people classed as severely addicted, who were given one of three different doses of CBD or placebo capsules, as well as psychological support.
The lowest dose didn’t work. The middle dose of 400 milligrams worked best, said Curran. After six months it halved the amount of cannabis people used compared with placebo, as shown by tests for THC in their urine. And the highest dose of 800 milligrams was slightly less effective than the middle one.
The 400 milligram dose also more than doubled the number of days when people had no THC in their urine. “That’s really remarkable,” said Curran.
CBD supplements are increasingly sold in pharmacies and health food stores as remedies for a range of illnesses, but at much lower doses than were used in the trial. And most of the health claims are not based on evidence.
Curran’s team has also found preliminary evidence that CBD may help smokers quit.