An experimental drug which can help beat cannabis withdrawal symptoms that make it hard for heavy users to quit could be in increasing demand as the legalisation movement gains pace, scientists have said.

Yale University researchers have found the treatment helped reduce withdrawal symptoms, like sleep disruption, anxiety, and irritability – and reduced their cannabis use more than subjects given a placebo.

The treatment works by preventing the breakdown of a chemical called anandamide, one of the cannabis-like endocannabinoids naturally occurring in the body that act on the same brain receptors as cannabis.

A much larger clinical trial is now underway to get a better picture of its effectiveness before it can apply to be licensed, but the researchers said the initial signs show it could help users quit.

“With an increase of marijuana legalisation efforts, it is reasonable to expect an increase in demand for treatment, and right now we don’t have any medications to help individuals trying to quit,” said Professor Deepak Cyril D’Souza, one of the study's authors.

“A lot of other drugs have been tested for their ability to reduce cannabis use and withdrawal, but until now none have been consistently shown to work against both withdrawal symptoms and relapse,” he added.

There is debate about how prevalent cannabis addiction is, while it can cause psychological and physical symptoms of withdrawal much of the research is muddied by cannabis being smoked with tobacco in joints.

Current estimates are that 9 per cent of users meet the criteria for cannabis dependence disorder which the American Psychiatric Association defines as use leading to risky behaviour, functional or social impairment and withdrawal.

Worldwide this is thought to affect 13 million people, but as many as a third of US users by some assessments. More than 250,000 people were admitted for cannabis abuse treatment in 2016 but only a fraction achieve long-term recovery.

The Yale researchers’ findings, published in the journal Lancet Psychiatry, tested their treatment in 70 men, as the toxicity of the drug in women has not been assessed yet, who smoked more than three joints a day on average.

It works by inhibiting an enzyme, called fatty acid amide hydrolase (FAAH) and allowing anandamide to build up, which the Yale researchers theorised could offset the cannabis withdrawal.

To test this they measured sleep patterns as well as cannabis use, via urine test, and asked users to assess the quality of their sleep, mood and cravings.

Currently only substitution therapies have shown much success in tackling withdrawal, but they often involve drugs that can also be abused or increase the risk of relapse.

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Throughout the trial men receiving reported better sleep and less anxiety and depression.

Measurements taken during sleep showed that patients receiving the placebo began to get significantly less deep sleep at night, immediately after the abstinence period began, while the treatment group improved.

Professor D’Souza and his team suggest that this sleep disruption could be a key factor which undermines patients ability to sleep.

While further tests are needed to validate these results, and to test things like memory or functional impairment and how long lasting the effects are, the treatment holds promises and is unlikely to lead to abuse.

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“Anandamide is to cannabis as endorphins are to heroin,” Prof D'Souza said.