Problem drug use (PDU) is defined as “recurrent drug use that is causing harm to an individual or is placing them at a high probability or risk of suffering harms”. This type of use often causes behavioural and physiological changes that may lead to the inability of an individual to control use of the drug. Substances associated with PDU include opioids, cocaine (powder and crack), amphetamines, benzodiazepines, Z-drugs and gabapentinoids. PDU can lead to many harms for populations and individuals, such as increased criminal activity, drug-related litter, increased risk of infectious diseases passed on from shared syringes and needles, substance use disorders, overdoses and death.

One of the five strategic goals within the Irish national drugs strategy is to “develop sound and comprehensive evidence-informed policies and actions”. However, to date, studies on PDU in Ireland have largely been conducted at a national level or have concentrated on Dublin city. A proper assessment of PDU in Cork city is therefore needed. Thus, the objectives of this research were to provide estimates on the scale of PDU in Cork city using the most recent available data, and to compare trends over time.

Findings from a four-source capture-recapture analysis estimated that there were 859 (95% confidence interval [CI]: 774–1,079) problematic opioid users in Cork city in 2022, which equates to a prevalence rate of 5.59 (95% CI: 5.04–7.02) opioid users per 1,000 population. In 2022 almost one-third of opioid users in Cork city were unknown to services. Between 2019 and 2022 the prevalence of opioid use remained relatively stable, with a majority of users being male and between 35 to 64 years of age. However, the needle exchange programme in Cork city has shown a general increase in the number of syringes exchanged since 2019, with an average of 6,685 syringes being provided each month from pharmacy-based sites in 2023. Data from household surveys demonstrate an increase in recent use of cocaine (including crack) and amphetamines, with these increases being noticeably pronounced among young adults. The number of individuals entering treatment in Cork city for PDU declined between 2019 and 2023, and the main problem drug for cases entering treatment has shifted; since 2019, trends indicate a gradual reduction in the number of people entering treatment for opioids, with an increase in the number of individuals accessing treatment services for cocaine use.

For the years 2019–2023, benzodiazepines were the main drug implicated in non-fatal overdose cases in Cork city, followed by opioids, with an average of one opioid overdose occurring each week. Between 2018 and 2021 there was a total of 487 self-harm presentations related to PDU by Cork city residents; benzodiazepines were the main drug implicated in self-harm presentations (63.2%), followed by opioids (30.6%) and gabapentinoids (11.9%). During this period there was a total of 140 poisoning deaths due to PDU recorded, with an average of 35 deaths each year. Opioids were the main drug implicated in poisoning deaths, followed by benzodiazepines and gabapentinoids.

The results from this study demonstrate that PDU is taking place in Cork city, with a number of associated harms. Although Cork city has a variety of harm reduction services that deal with education, assessment, treatment and post-treatment support, the disconnect between problem drug users and these programmes may benefit from additional services. Ongoing research in this area will be crucial for effective service planning and to allow policymakers to evaluate the impact of strategies aimed at reducing drug-related harms.