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 percent 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.
Junior health minister Alex White said the survey - the third in a series of seven bulletins arising from data collected in 2010 and 2011 - was the best measure of the cannabis situation in both the Republic of Ireland and Northern Ireland.
"I would emphasise the dangers of cannabis use for physical and mental health, especially as the cannabis now available is much more potent than in the past," Mr White said.
Other findings in the report included:
Less than 1% of all adults - aged 15 to 64 - were classified as cannabis-dependent.
Around 9% of recent cannabis users were considered dependent on the drug. Dependence was higher among male and young adult recent users.
Just over 1% of all adults - aged 15 to 64 - fit the criteria for cannabis abuse.
Among recent cannabis users, 17% met criteria for abuse of the drug and again, rates were highest among male and young adult recent users.
Among those who reported ever using cannabis - classed as lifetime users - the average age of first use was 18 years.
Since the last survey in 2006/2007, the share of people using the drug frequently - 20 days or more in the month - has decreased, particularly among male and young adult current users.
The share of current cannabis users engaging in lowest frequency use (of one to three days in the month - has increased.
The majority of recent cannabis users said it would be easy for them to obtain cannabis in a given 24-hour period.
The majority of lifetime cannabis users said they had never used the drug on a regular basis. Of those who have, most said they had stopped using.
The three most common reasons given for stopping cannabis use included not wanting to take it anymore, it no longer being a part of the person's social life and health concerns.
Most respondents agreed that cannabis use should be permitted for medical reasons, most disagreed it should be allowed for recreational reasons, most disapproved of smoking cannabis occasionally, and most considered smoking it on a regular basis to be risky.
Rates for lifetime cannabis use were highest among professionals and managers, and lowest among the semi-skilled and unskilled.