title: Introduction to observational studies: part 1.
authors.affiliation: Bern, Switzerland, and Corfu, Greece.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Pandis
mesh_terms: D003430:Cross-Sectional Studies; D003625:Data Collection; D006801:Humans; D008137:Longitudinal Studies; D064887:Observational Studies as Topic / Q000145:classification; D011446:Prospective Studies; D012107:Research Design / Q000706:statistics & numerical data; D012189:Retrospective Studies