Prof John has worked in the field of psychological health for many years, in research, teaching and treatment delivery, developing and evaluating health related interventions. She has also delivered psychological therapies. Her main focus is applied research in psychological health, in particular promoting positive behaviour change in mental and physical health and substance misuse; and the development and evaluation of psychological interventions. She has developed assessment and screening instruments that are now recommended in NICE guidelines (e.g. FAST alcohol screening test). She has extensive expertise in a wide range of research methodologies, including quantitative, qualitative and desk based approaches. She has contributed to policy developments and the public debate on alcohol and gambling harm; and has published widely in peer reviewed journals and other relevant media.