The PEPs project was a multicentre, naturalistic, two-year longitudinal study that investigated the clinical, neuropsychological, neuroimaging, biochemical, environmental, and pharmacogenetic risk factors associated with first-episode psychosis. The study involved a sample of 335 first-episode psychosis patients and 253 healthy controls. Between 2009 and 2011, patients aged 7 to 35 years old who presented with first lifetime psychotic symptoms for at least one week in the last 12 months were recruited from 16 participating centres throughout Spain. A sample of healthy controls matched for age, sex, ethnicity, and handedness was also recruited from the same geographic areas as the patients. Patients were assessed on five occasions: at recruitment (baseline), and after two months, six months, one year, and two years. Controls were only assessed at baseline and two years.