A new study from the Department of Health has shown almost 25% of people who have used cannabis in the past year are classified as 'cannabis dependent'.
The 'Drug Use in Ireland and Northern Ireland' survey reveals a slight increase in illegal drug use overall.
It shows levels are up by 1.9% between 2010/11 and 2014/15.
The data was collected in the fourth Drug Prevalence Survey.
Results indicate cannabis continues to be the most commonly used illegal drug.
While the use of new psychoactive substances (NPS) has dropped significantly.
Key findings of the cannabis results show that 26.4% of Irish adults aged 15+ report using an illegal drug in their lifetime - with 7.5% using an illegal drug in the past 12 months.
Among people who used cannabis in the last year, 24.3% are classified as 'cannabis dependent'.
The report notes that cannabis dependence is higher in men who used in the last year than women (26.8% vs. 16.7%).
Among people who used cannabis in the last year, 32.1% meet the criteria for 'cannabis abuse'.
Rates of cannabis abuse are also higher in men (33.9%) than women (26.4%).
Most respondents (74.5%) agree that people should be permitted to take cannabis for medical reasons.
Older adults are more likely to agree than young adults (78.4% vs. 73.9%) and over-65s (64.2%).
Prescription drugs
The study also showed that the prevalence of prescription drugs was highest in Ireland among women and the elderly - with 8% of women and 8% of those aged 35-64 reporting use of sedatives or tranquillisers.
Anti-depressants prevalence is also highest for both groups, at 7%.
The report says: "Most people obtain these medications from their GP.
"There are indications that some people could be taking them in a way that is counter to recommended practice guidelines and thereby putting their health and well-being at risk."
A doctor holds blister packs with different drugs | Image: Klaus Ohlenschläger/DPA/PA Images
While almost one-fifth (19.9%) of Irish adults have used other opiates in the past month, with 43.4% doing so in the past 12 months and 61.5% having done so at some stage during their life.
The use of other opiate is significantly higher among women across all the timeframes.
Minister for Health Promotion, Catherine Byrne, says: "I welcome the publication of the findings of these three surveys, which serve to inform us of trends in drug use and inform policy formulation and future planning and action."
"A number of actions in 'Reducing Harm Supporting Recovery' address the survey findings, especially the continuing need for preventative measures that focus on young people.
"The strategy commits to developing targeted, appropriate and effective services for young people at risk of substance misuse, focused on socially and economically disadvantaged communities."
