“…The target population as any person who was injured in the March 11 attacks and seen at the emergency rooms of 4 large hospitals: Gregorio Marañón (HGM), 12 de Octubre (H12O), La Princesa (HP) and Príncipe de Asturias (HPA) between 8:00 a.m. and the midnight of March 11, 2004. Approximately 1400 people were injured in the terrorist attacks; 754 (54%) of these were seen in one of these 4 hospitals: 41%, 35%, 13%, and 9.5%, respectively [32,31]. We drew a proportional random sample of 132 subjects from the 754 injured persons seen at these 4 hospitals.…”