Researchers at Bern University hospital have released a study that shows prolonged and regular use of cannabis can severely damage a smoker's lungs.
The results come just after a Lausanne team revealed that an occasional puff was unlikely to harm a student's grades.
The Bern researchers took an interest in young adults who were admitted for treatment of collapsed lungs or emphysema. These patients' lung tissue was severely damaged and the type of emphysema found is unusual in younger people.
Ralph Schmid, head of thoracic surgery at the hospital, spent two-and-a-half years with his team finding what might be the cause of these diseased lungs.
Seventeen patients – 16 men and one woman – were the focus of the study. Their average age was 27 and all admitted to being regular cannabis users.
The research included x-rays, scans, a complete medical history and a check of lung function and tissue. A control group of 85 cannabis abstainers aged around 24 underwent the same tests, and the results were compared with an earlier study.
The focus group had smoked on average six joints a day over a period of more than eight years and also consumed cigarettes on a daily basis for nearly 12 years.
The tests were unable to show which substances had caused the lung damage, but cannabis fibres were found in the tissue samples and can constitute the starting point for inflammation. Another study from New Zealand researchers warned earlier this year that the effect on a person's lungs of smoking one joint was equal to up to five cigarettes.
There were also no cases of emphysema in the control group, even though it included 74 regular smokers.
In an article to be published in the European Journal of Cardio-thoracic Surgery this week, Schmid and his co-authors warn that regular daily use of cannabis can lead to severe lung damage and breathing problems.
While patients can undergo surgery to alleviate their breathing problems, the researchers said that in some cases a lung transplant is the only long-term solution.
Their report comes a few days after Lausanne researchers published a study stating that occasional cannabis use by youngsters is unlikely to cause psychosocial problems.
Based on a survey of more than 5,000 teenagers from all over Switzerland, the study showed that those who smoke the drug just once or twice a month and nothing else are no worse off than their peers who abstain altogether.
The results seem to show that they also have better relationships with their friends and do more sport – but their relationships with their parents are more problematic.
But the researchers, who did not explain the reason for these findings, warn that cannabis use should not be trivialised since it could lead to harder drugs or nicotine addiction.
But they also said parents should not over-react when their children occasionally use marijuana.
swissinfo with agencies
Cannabis in Switzerland
A United Nations report issued earlier this year found Swiss cannabis consumption and production were on the rise. Almost 10% of 15 to 64-year-olds use the drug, it said.
But a Swiss Institute for the Prevention of Drug and Alcohol Problems survey in February showed the first fall in cannabis consumption for 15-year-olds in 20 years.
A 2002 Swiss health questionnaire found that 28% of people surveyed aged 15-39 had smoked cannabis at least once in their life.
A group of politicians and drug experts launched an attempt to decriminalise cannabis last year. They want to force a nationwide ballot on making the purchase, possession and consumption of the drug legal under controlled conditions. A vote is not expected until at least next year.
Cannabis and health
On the mental health front, a recent Zurich University study claiming a link between cannabis use and schizophrenia stirred debate in Switzerland.
The researchers said their results showed a direct link between the disease and smoking marijuana.
But the Federal Health Office was not convinced, stating that there was a lack of data concerning the patients' medical histories or whether they consumed psychotic substances to back up the research.
Another study from New Zealand researchers also warned earlier this year that the effect of smoking one joint on a person's lungs was equal to up to five cigarettes.