Trends and characteristics of Opioid, Gabapentinoid and Antidepressant co-prescribing (TOGA)

Chronic pain affects millions of people in the UK and is frequently treated using combinations of medications such as opioids, gabapentinoids (gabapentin and pregabalin) and antidepressants. While these drugs can be beneficial, each carries known risks, including overdose and in some cases, death. These risks may be amplified when medications are taken together. However, despite widespread co‑prescribing, there remain substantial gaps in our understanding of which drug combinations are most harmful, which groups are most affected, and how prescribing patterns have changed over time, particularly following major regulatory interventions.

This PhD studentship will investigate the trends and characteristics of Opioid, Gabapentinoid and Antidepressant co‑prescribing. The project is designed to generate robust evidence that can directly inform safer prescribing, guide policy and ultimately improve outcomes for people living with chronic pain.

Project overview

This PhD will combine systematic review and large‑scale linked health data analysis. The successful applicant will explore:

• How often opioids, gabapentinoids and antidepressants are prescribed together across the population.
• How these prescribing patterns have changed over time, including the impact of the 2019 UK reclassification of gabapentinoids as controlled drugs.
• Social, demographic and clinical factors associated with co‑prescribing, with a particular focus on sex‑based differences.
• Associations between co‑prescribing and adverse outcomes, including hospitalisation, overdose and mortality.
• Which drug combinations pose the greatest risks, and for whom.

The student will work with high quality linked NHS datasets from across Scotland. These include prescribing data, hospital admissions, emergency department attendances and national death registrations, offering unparalleled opportunities for population‑level research.

Methods and training

The project will begin with a systematic review and meta‑analysis synthesising existing evidence on co‑prescribing. The main component is a retrospective cohort study using securely linked electronic health records. Analytical training and methods will include:

• Interrupted time‑series analysis
• Multivariable modelling
• Cox proportional hazards models
• Advanced statistical techniques using R (or other similar packages)

You will receive comprehensive training in epidemiology, health data science, biostatistics, systematic review methodology, research governance, Public and Patient Involvement and Engagement (PPIE) and interdisciplinary collaboration.

Research environment

The successful applicant will join the Chronic Pain Research Group, part of the Division of Population Health and Genomics, within the Faculty of Health at the University of Dundee. Our group is located at Ninewells Hospital and Medical School, one of Europe’s largest teaching hospitals and a major centre for clinical training, translational research and multidisciplinary collaboration. The School of Medicine offers outstanding facilities, including modern teaching spaces, world‑class clinical research infrastructure and access to rich, high quality health data through the Health Informatics Centre (HIC).

PhD students benefit from a supportive and well‑resourced training environment. The Doctoral Academy provides opportunities for skills development in statistics, academic writing, data management, open science and research impact.

New researchers in the School of Medicine are supported through the Buddy and CONNECT peer mentoring schemes, matching starters with those further along in their studies, helping them integrate into the research community.

Students can also engage with the wider early‑career researcher community through the Research Staff and Student Association (RSA), which offers seminars, development activities and social events, fostering an inclusive and collaborative research culture across the University.

Candidate requirements

Applicants must hold, or be predicted to achieve:

• At least an Upper Second Class (2:1) undergraduate degree in a relevant discipline (e.g., epidemiology, biomedical sciences, public health, statistics, psychology, pharmacology, data science, medicine),

or

• A 2:2 undergraduate degree with a relevant Master’s degree.

This PhD is ideal for candidates with an interest in health data research, pain medicine, epidemiology, or pharmacological safety who want to make a meaningful contribution to public health and clinical practice.

Impact

• The findings from this project will:
• Provide new evidence to support safer prescribing practices.
• Identify high‑risk combinations and vulnerable population groups.
• Inform national policy and future clinical guidelines.
• Contribute to efforts to reduce drug‑related harm, particularly in regions heavily affected by opioid and gabapentinoid‑related deaths.
• Lead to high quality publications and conference presentations.

Start Date: 1 September 2026

References

1. Ashworth J, Bajpai R, Muller S, Bailey J, Helliwell T, Harrisson SA, Whittle R, Mallen CD. Trends in gabapentinoid prescribing in UK primary care using the Clinical Practice Research Datalink: an observational study. Lancet Regional Health Europe 2023;27:100579. DOI: 10.1016/j.lanepe.2022.100579.
2. Fayaz A, Croft P, Langford RM, Donaldson LJ, Jones GT. Prevalence of chronic pain in the UK: a systematic review and meta-analysis of population studies. BMJ Open 2016; 6(6):e010364. DOI: 10.1136/bmjopen-2015-010364.
3. Glancy M, Palmateer N, Yeung A, Hickman M, Macleod J, Bishop J, Barnsdale L, Trayner KM, Priyadarshi S, Wallace J, Hutchinson S, McAuley A. Risk of drug-related death associated with co-prescribing of gabapentinoids and Z-drugs among people receiving opioid-agonist treatment: A national retrospective cohort study. Psychiatry Research 2024;339:116028. DOI: 10.1016/j.psychres.2024.116028.
4. Hébert HL, Morales DR, Torrance N, Smith BH, Colvin LA. Assessing the impact of a national clinical guideline for the management of chronic pain on opioid prescribing rates: a controlled interrupted time series analysis. Implementation Science 2022; 17(1):77. DOI: 10.1186/s13012-022-01251-2.
5. Hébert HL, Veluchamy A, Baskozos G, Fardo F, Van Ryckeghem D, Pearson ER, Colvin LA, Crombez G, Bennett DLH, Meng W, Palmer CNA, Smith BH. Development and external validation of multivariable risk models to predict incident and resolved neuropathic pain: a DOLORisk Dundee study. Journal of Neurology 2023;270(2):1076-1094. DOI: 10.1007/s00415-022-11478-0.
6. Muller S, Bailey J, Bajpai R, Helliwell T, Harrisson SA, Whittle R, Mallen CD, Ashworth J. Risk of adverse outcomes during gabapentinoid therapy and factors associated with increased risk in UK primary care using the clinical practice research datalink: a cohort study. Pain 2024; 165(10):2282-2290. DOI: 10.1097/j.pain.0000000000003239.
7. Soliman N, Moisset X, Ferraro MC, de Andrade DC, Baron R, Belton J, Bennett DLH, Calvo M, Dougherty P, Gilron I, Hietaharju AJ, Hosomi K, Kamerman PR, Kemp H, Enax-Krumova EK, McNicol E, Price TJ, Raja SN, Rice ASC, Smith BH, Talkington F, Truini A, Vollert J, Attal N, Finnerup NB, Haroutounian S; NeuPSIG Review Update Study Group. Pharmacotherapy and non-invasive neuromodulation for neuropathic pain: a systematic review and meta-analysis. Lancet Neurology 2025;24(5):413–28. DOI: 10.1016/S1474-4422(25)00068-7.
8. Torrance N, Mansoor R, Wang H, Gilbert S, Macfarlane GJ, Serpell M, Baldacchino A, Hales TG, Donnan P, Wyper G, Smith BH, Colvin L. Association of opioid prescribing practices with chronic pain and benzodiazepine co-prescription: a primary care data linkage study. British Journal of Anaesthesia 2018; 120(6):1345-1355. DOI: 10.1016/j.bja.2018.02.022.
9. Torrance N, Veluchamy A, Zhou Y, Fletcher EH, Moir E, Hebert HL, Donnan PT, Watson J, Colvin LA, Smith BH. Trends in gabapentinoid prescribing, co-prescribing of opioids and benzodiazepines, and associated deaths in Scotland. British Journal of Anaesthesia 2020;125(2):159-167. DOI: 10.1016/j.bja.2020.05.017.

• Three-year British Journal of Anaesthesia / Royal College of Anaesthetists Non-Clinical PhD Studentship
• Stipend: £20,780 per annum (MRC rates)
• Funding covers tuition fees (UK only) and research costs 

External supervisor

Dr Louise Marryat