A bizarre syndrome that makes heavy cannabis users violently ill and leads them to take frequent hot baths to ease the pain has been reported by doctors.
Symptoms of the illness include severe stomach pain, nausea and vomiting - and bathing in very hot water up to five times a day for relief.
At least two cases of the syndrome which involve multiple visits to accident and emergency have been reported in the UK and worldwide the conditions is 'increasing acutely'.
But doctors in the UK warn that the failure to recognise CHS is likely to be draining hospital resources as it is being wrongly diagnosed.
Dr Sauid Ishaq, professor of gastroenterology at Birmingham City University, who was one of the first to observe the syndrome in the UK said: 'This is a highly unrecognised condition, resulting in numerous unnecessary admission.
'There is an urgent need to highlight this.'
In the US, doctors in Colorado report an 'acute' rise in cases of the syndrome there since marijuana laws became relaxed.
CHS, which stands for cannabinoid hyperemesis syndrome, was first reported in medical literature in 10 patients in Adelaide, Australia in 2004.
Recognition of the condition is increasing and doctors are now recognising the condition in patients regularly visiting hospital with severe nausea.
Dr Ishaq reported a 42-year-old man presented on eight occasions with vomiting, abdominal pain, fever and dehydration last year in the east Midlands.
Dr Ishaq of Russells Hall Hospital, Dudley and colleagues found the man had been a chronic cannabis smoker since the age of 14.
After a series of investigations, they found the symptoms ceased when the patient stopped smoking the drug.
Dr Sauid Ishaq, who was one of the first to observe the syndrome in the UK said: 'This is a highly unrecognised condition, resulting in numerous unnecessary admission' (File image posed by a model)
In the medical journal GHFBB the authors write better awareness of the condition 'would result in fewer hospital admissions and needless investigations, and may provide patients with real motivation to abstain from cannabis'.
At Macclesfield General Hospital, a 21-year-old chef had been admitted on seven occasions over a two year period with profuse vomiting - but his symptoms ended after he stopped smoking the drug.
Cannabinoid hypermesis syndrome is characterised by heavy use of the drug, triggering nausea and vomiting as well as frequent hot baths or showers.
Despite studies promoting the use of marijuana's anti-emetic (anti-sickness) qualities, there is increasing evidence of its negative affect on the gastrointestinal tract, triggering CHS.
Sufferers have reported frequent hot bathing helps to provide temporary relief from the nausea, vomiting and abdominal pain typical of the illness.
Lead author Dr Enrico Roche wrote in the journal Gut: 'The observation that the patient wanted to take regular baths because he had found that bathing eased the sickness was documented in the nursing notes but its significance was not appreciated.'
In one case reported in the Journal of American Family Medicine a man 'spent three days in a hot shower while awake' to alleviate his symptoms.
His case was not the most extreme however, as researchers reported that one sufferer reported spending '300 out of 365 days' in the bath.
The findings that cannabis can cause severe nausea runs counter to a widespread view that the drug has a powerful anti-nausea effect.
Doctors in Colorado - where cannabis has been legalised - suspected that some of the cases of extreme nausea they had been seeing may have been caused by chronic cannabis use.
They reviewed admission data to hospitals and found an acute rise in the condition since marijuana became legalised and widely available for medical use.
The research, in Academic Emergency Medicine, compared the numbers of people suffering from the condition from November 1, 2008 to October 31, 2009, after which cannabis use became liberalised in the state and between June 1, 2010 to May 31, 2011.
They found 41 cases of suspected CHS - where patients had been admitted three or more times for nausea - before legalisation rose to 87 cases after legalisation at two hospitals, Denver Health and the University of Colorado.
The sufferers were predominantly female (71 per cent) and white (72 per cent) with an average age of 31, the authors note.
The authors, led by Dr Kim Howard, wrote they think that the most likely explanation for the marijuana use contributed to an increased rate of cyclic vomiting presentations.
Marijuana is the most commonly used illicit substance in the United States, the authors note, with 18.9 million users in 2012.
But they add: 'Unfortunately, there is little information on the deleterious effects of chronic use and its implications for public health.
'As the number of new and chronic marijuana users grows annually, it is important to measure its effect on public health...the rate of cyclic vomiting seems to have increased acutely.'
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