Opioid dependence in Scotland remains high but largely stable, study shows

Opioid dependence in Scotland remains high but largely stable, according to a new University of Bristol-led analysis published in Addiction today [18 April] and by Public Health Scotland. The study is the first to estimate the number of people dependent on opioid drugs (such as heroin), and who are in or could benefit from drug treatment, among Scotland's population since 2015/2016 estimates were published.

Scotland has one of the highest rates of drug-related deaths in Europe, with the number of these more than doubling between 2011 and 2020. At 250-300 per million population in 2021-22, Scotland's rate of drug-related deaths was sixteen times higher than the average in the European Union and on par with rates in North America. As part of the response to the public health emergency in drug-related deaths, the Scottish Government-commissioned study sought to understand whether the number of people with opioid dependence among its general publication is also increasing.

To predict how many people aged 15 to 64 years old are opioid dependent, researchers from Bristol's National Institute for Health and Care Research Health Protection Research Unit (NIHR HPRU) in Behavioural Science and Evaluation applied a statistical modelling technique using data from Public Health Scotland's Scottish Public Health Drug Linkage Programme, including information on people in drug treatment called opioid agonist treatment (OAT – primarily methadone and buprenorphine) and data on opioid-related mortality and hospital admissions.

In these new estimates, researchers found the prevalence of opioid dependence in Scotland to have been relatively stable between 2014/15 to 2019/20, with 47,100 people estimated to be opioid-dependent in 2019/20 – which is 1.3 per cent of the adult population aged 15-64.

While there was weak evidence of a small reduction in the total number of people with opioid dependence since 2014/15, the extent of any change was estimated to be small (-0.07 per cent or -2,000 people). There was evidence that the population of people with opioid dependence were ageing, with estimates of the number of people aged 15 to 34 years old reducing by 5,100 and the number aged 50 to 64 years old increasing by 2,800 between 2014/15 and 2019/20.

The research team also estimated that over 60 per cent of the population of people who were opioid-dependent received OAT at least once during 2019/20 and nearly 75 per cent had been in drug treatment in the last five years.

Dr Hayley Jones, Associate Professor in Medical Statistics in the Bristol Medical School: Population Health Sciences (PHS), lead author and developer of the method (Multi-Parameter Estimation of Prevalence) used in Scotland, said: "This is the first time that trends in the prevalence of people with opioid dependence have been produced in Scotland, showing the value of and making the most of the high-quality linked data sets that are available there.

"The method can be used to update the estimates in future, and can be applied in other countries that create comprehensive records of people in drug treatment and link these to data on drug-related harms."

Importantly, our estimates suggest the substantial increase in drug-related deaths in Scotland is not due to increases in the underlying population of people with opioid dependence but because of increases in the risk of death experienced by people with opioid dependence in Scotland."

Professor Matt Hickman, co-first author and director of the NIHR HPRU at the University of Bristol

Professors Sharon Hutchinson and Andrew McAuley, co-authors and lead researchers at Glasgow Caledonian University, explained: "We showed that exposure to drug treatment in Scotland is high compared to many countries worldwide. The challenge in Scotland and rest of UK, however, is to retain people in drug treatment for longer and to determine what other interventions are required to effect change at the population level – and bring down the number of drug-related deaths."

The public health surveillance study, commissioned by the Scottish Government, is a collaboration between Public Health Scotland, the University of Bristol, and Glasgow Caledonian University.