Drug prevalence: New research

A Capture-Recapture Study to Estimate the Prevalence of Problem-Opioid Use in Ireland (2020 – 2022)

A research project by the School of Public Health at University College Cork, commissioned by the Health Research Board



Opioid use is a major problem in Ireland. It is therefore important for government and support agencies to know how many people are impacted by the negative effects of opioids on a regular basis. The most recent figures from 2019 estimate that there are between 19,522 – 21,608 problematic opioid users in Ireland.

The Health Research Board (HRB) has commissioned a team from the School of Public Health in University College Cork (UCC) to estimate how many people used opioids in Ireland between 2020 – 2022. To calculate the numbers, we’ll use information from methadone prescribers and the Irish Probation Service.

Why is this Research Important?

This research will provide information to services who support people who use drugs. It will also help inform policy development in Ireland. This project is a continuation of work conducted over the last 20 years and will allow us to examine changes in opioid use in Ireland over time. This will help government and support agencies predict where services will be needed in the future.


The overall aim of this project is to provide an up-to-date estimate of how many people use opioids in Ireland between 2020 – 2022.


We will be using a type of indirect statistics to conduct this research as we know it will not be possible to count all people who use opioids. This method is known as the “capture-recapture method”. To do this, we will access information from the National Drug Treatment Centre and the Irish Probation Service.

Personal data such as name, date of birth, gender and address will be collected from various agencies (listed above). This is to make sure the same person is not counted twice. No other information about a person’s drug use will be collected. Once the data are received and checked they will be fully anonymised and not shared with any third parties.

Ethical Approval, Consent Declaration and Data Protection

For this research it is very important that we can count everybody that links with the National Drug Treatment Centre and Probation Service. We will check personal details to make sure that we are not counting the same person twice and anonymise the data immediately after that. Withdrawal of personal data from the study is limited. This is because only by accurately counting every person that accesses support for their opioid use can we inform services who can then develop policies to respond to their needs.

This research has received ethical approval from the Clinical Research Ethics Committee of the Cork Teaching Hospitals and a consent declaration approved by the Health Research Consent Declaration Committee (HRCDC). This approval means that we don’t have to contact every single person included in the study for individual consent.

For More Information

For further information on personal data processing rights, please contact UCC’s Data Protection Officer by email at gdpr@ucc.ie.

To learn more about this study please contact the Research Support Officer for this project - Dr Michael Hanrahan, michael.hanrahan@ucc.ie


This project is funded by the Health Research Board.