July effect

The July effect, sometimes referred to as the July phenomenon, is a perceived but scientifically unfounded increase in the risk of medical errors and surgical complications that occurs in association with the time of year in which United States medical school graduates begin residencies. A similar period in the United Kingdom is known as the killing season or, more specifically, Black Wednesday, referring to the first Wednesday in August when postgraduate trainees commence their rotations. In reality, this phenomenon has not been proven in the scientific literature. In fact, large-scale meta analysis, which has aggregated over 110 studies on this topic, has shown no evidence of a July effect on mortality, morbidity, or readmission.