Felix is a registered Health Psychologist, Professor of Health Psychology and co-lead of the UEA Addictions Research Group. He is a world leader in the development and evaluation of digital interventions to promote and support health behaviour change. His particular interest is in innovative technology-mediated approaches, such as Just-In-Time Adaptive Interventions and more recently chatbots for behaviour change. He leads a research programme focused on developing innovative digital stop smoking interventions. This includes an ongoing 6-year NIHR-funded research programme converting specialist stop smoking support in pregnancy into a comprehensive digital support package (eSupport). He also currently leads the Enhancing QUALitative health psychology with AI (EQUAL) network, funded by an Innovative Initiatives grant from the European Health Psychology Society (EHPS).

Felix has collaboratively developed and evaluated multiple mHealth interventions including individually tailored SMS text messaging systems for smoking cessation (MiQuit and iQuit in Practice systems) and the world’s first context aware smoking cessation smartphone app (Quit Sense). He also oversaw the development of a blended face-to-face and digital Nicotine Replacement Therapy (NRT) adherence intervention for pregnant smokers in collaboration with researchers from UEA and the University of Nottingham (Baby, Me and NRT; being evaluated in the SNAP 2 trial). He is also involved in multiple mHealth and digital health projects with national and international collaborators (including Europe, USA, India and Australia) as well as projects exploring the potential of vaping for smoking cessation and vaping cessation. He also specialises in N-of-1 (single case) experimental and observational methods to better understand individual differences in health behaviour change.

Felix is a past President and current Honorary Secretary of the Society for Research on Nicotine and Tobacco Europe (SRNT-E), a Fellow of the Society for Research on Nicotine and Tobacco (global) and a Fellow of the European Health Psychology Society (EHPS). He has served as a topic expert for the National Institute for Health and Care Excellent (NICE) 'Behaviour change: digital and mobile health interventions' (NG183) and the 'Tobacco: preventing uptake, promoting quitting and treating dependence' (NG209) advisory committees and has been appointed as an expert advisor for the NICE Centre of Guidelines. He is a Senior Editor at the journal Addiction and was awarded an academic fellowship from the Society for the Study of Addiction (2014-2016). He is also a chartered member of the British Psychological Society (BPS), a full member of the Division of Health Psychology (DHP) and a Senior Fellow of the Higher Education Academy (SFHEA). He has served on multiple scientific committees, including the DHP, the EHPS (co-chair 2022), SRNT-E and the Centre for Behaviour Change (co-chair 2019, 2020, 2026). He also served as a standing member of Cancer Research UK’s Expert Review Panel for the Prevention and Population Research Committee (PPRC) panel.