25% of adults have used cannabis
A quarter of adults have used cannabis with highest usage rates among those with a further education, new figures have revealed.
A study of the use of the illegal drug on the island of Ireland found it had increased from 22% in 2007 to 25% in 2011.
Professor Catherine Comiskey, chair of the National Advisory Committee on Drugs and Alcohol, which carried out the drug prevalence survey, said cannabis continues to be the most commonly used illegal drug in the country.
"The survey indicates that in the general population, people are quite tolerant of the use of cannabis for medicinal reasons, but less so for other use," Prof Comiskey said.
She said while lifetime use of the drug has increased, it is now used less frequently than before.
The report considered people's use of cannabis over a lifetime, in the last year and in the last month of the survey. It also looked at people's age at first use, methods of taking the drug and how it is obtained.
Six per cent of those surveyed said they had used the drug in the last year, 3% in the last month, and the proportion of all adults reporting the highest frequency of use - of 20 days or more in the month - dropped from 24% to 14%.
Men aged 15 to 24 were more than twice as likely as women to use cannabis in the last year. Prevalence rates were highest among men and younger adults - aged 15 to 34. While the number of men using the drug had increased from 2007, rates among women remained fairly steady.
The results of the survey - entitled Drug Use in Ireland and Northern Ireland Drug Prevalence Survey 2010/2011: Cannabis Results - also revealed that cannabis use was more common among those with a further education.
Rates were highest among people who were still in education over the age of 20 and lowest among those who left education before the age of 15. A marked switch from cannabis resin to herbal cannabis was also identified.