We identified valproate, lamotrigine, and levetiracetam drug users via verbal baseline interview and primary care prescription data, allowing us to capture drug prescriptions within a time period between 1978 to 2018. We have previously reported the details of our pipeline to extract medication data from UKB primary care data.14 (link) First, all available ever-approved formulations for valproate, lamotrigine, and levetiracetam were gathered by using international nonproprietary (INN) names, former and current trade names in the UK (via the National Health Service Dictionary of Medicines and Devices [DM+D] browser, https://services.nhsbsa.nhs.uk/dmd-browser/search), and their associated DM+D and British National Formulary (BNF) codes (Supplemental Table S1). Then, all primary care prescription data and the verbal interview data were searched for these formulations. Individuals were considered as users of a drug if they reported intake of one of the formulation names containing the drug at any verbal interview (baseline or follow-up, UKB field 20003) or if they had two or more prescriptions of a formulation containing the drug in the primary care data (gp_scripts table). The first drug prescription date for each individual was defined either as the first prescription date from primary care data or as the verbal interview date, whichever was earlier and available. To assess whether patients were on monotherapy or had other antiepileptic drugs prescribed, we extracted prescriptions for the most common antiepileptic drugs (Supplemental Table S1) between first prescription of valproate and end of follow-up.