Area level deprivation will be assigned to each patient using their home address postcode and to each GP practice using the practice postcode. Deprivation levels will be based on the Indices of Multiple Deprivation (IMD) which are available from the Office of National Statistics. IMD statistics are updated every two years. The investigators will use the most recent IMD statistics preceding the date of entry into the study for each patient. Although area level deprivation statistics will only be a proxy for individual level deprivation, these demonstrate the expected associations with smoking prevalence. By using both individual and GP level IMD codes, the investigators will investigate whether the effects of smoking cessation therapies differ by IMD at both the level of GP practice and at the individual level. For each patient, the investigators will investigate treatment compliance by reporting the total number of prescriptions issued after the initial prescription.