A snapshot survey of school-going teen-agers has found that a large number of them have admitted using cannabis.
Although the survey was confined to Cork it serves as a wake-up call for schools and parents in other parts of the country also.
More than a third of the 500 secondary school students who were surveyed admitted they had used cannabis.
The teenagers, from both fee-paying and state schools, viewed cannabis as low risk compared to other drugs, the findings from the School of Medicine in UCC showed.
While they had a good overall level of knowledge of the effects of cannabis they had a notable lack of awareness about its link to increasing the risk of schizophrenia.
The great majority of teenagers believe they are not given enough information about the drug, the meeting at the Royal College of Physicians was told.
The authors said cannabis is "extremely widespread among teenagers in Cork but there are relatively low levels of perceived risk of mental and physical health problems with its use".
The European Monitoring Centre for Drugs and Drug Addiction estimates that there are at least four million Europeans (one per cent of all adults) using cannabis on a daily or almost daily basis.
Most of these are males, reaching up to five to seven per cent of young men (15-34 years) in some countries.
A survey by the National Advisory Committee on Drugs in Ireland here in 2006-2007 reported that 6.3pc of the general population had used cannabis in the previous year.
The number of cannabis users attending treatment increased from 991 in 2003 to 1,191 in 2008, when it represented nearly one in five of those seeking help for addiction.
Independent TD Luke 'Ming' Flanagan, who has campaigned for the legalisation of cannabis, recently said he was kicking the habit after gardai called for him to be prosecuted for breaking the law.
He said he took the decision to quit smoking the drug to protect his wife and children from further media scrutiny, as he did not want them to see gardai coming to his house.
The problem is that too many people still believe cannabis is harmless yet it has been linked to a increased risk in users developing psychotic illness where they lose touch with reality.
Just like tobacco it can contain a lot of chemicals which with long-term or heavy use can lead to lung disease and possibly cancer.
Experts warn that the risk is higher because cannabis is often mixed with tobacco and smoked without a filter so this affects asthmatics and can lead to wheezing.
Other risks include damaging the ability to concentrate, decreasing motivation, while teenagers who use it regularly can have their psychological development affected.
People who abuse skunk, a stronger and increasingly more available form of cannabis, are seven times more likely to develop a psychotic illness.