Paul's research focuses on behavioural medicine. This is the integration of biological, psychological and sociological knowledge to prevent and treat disease and to aid rehabilitation.

His work focuses on helping people change their behaviour, either to prevent serious disease, or as a treatment for that disease.  

A lot of his work has examined interventions to help people stop or reduce their smoking and lately he has worked in helping people manage their weight if they have become obese. 

People often use several drugs to help them stop smoking but our research suggested that combining these drugs does not help more than taking only one of them. Their research has shown that people who stop smoking put on a considerable amount of weight and we are investigating the best ways to prevent this weight gain but without harming the chance of stopping smoking.