The investigators will define service use as the number of visits to GP and hospitals in the 3, 6, 9, 12, 24 and 48 months after first prescription. The investigators will define the GP appointments using the clinical data file of the CPRD. This includes all the diagnoses and symptoms that GPs record about all of their patients. As with the other outcomes, the vast majority of diagnoses and symptoms include the date on which the data were added to the database. The investigators will use these dates to define visits to primary care. The investigators will define the hospital visits outcome using the linked Hospital Episodes Statistics data. This is available for approximately half of the sample. Again these data contain the date on which the event occurred, which the investigators will use to define attendance to secondary care within 3, 6, 9, 12, 24 and 48 months after first prescription.