The July effect, sometimes referred to as the July phenomenon, is a perceived but scientifically unfounded increase in the risk of
medical error
A medical error is a preventable adverse effect of care ("iatrogenesis"), whether or not it is evident or harmful to the patient. This might include an inaccurate or incomplete diagnosis or treatment of a disease, injury, syndrome, behavior, i ...
s and
surgical complication
A complication in medicine, or medical complication, is an unfavorable result of a disease, health condition, or treatment. Complications may adversely affect the prognosis, or outcome, of a disease. Complications generally involve a worsening i ...
s that occurs in association with the time of year in which United States
medical school
A medical school is a tertiary educational institution, or part of such an institution, that teaches medicine, and awards a professional degree for physicians. Such medical degrees include the Bachelor of Medicine, Bachelor of Surgery (MBBS, MB ...
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.
United States
A ''
Journal of General Internal Medicine
The ''Journal of General Internal Medicine'' is a monthly peer-reviewed medical journal established in 1986 and covering internal medicine. It is published by Springer Nature and is the official journal of the Society of General Internal Medici ...
'' study, published in 2010, investigated medical errors from 1979 to 2006 in United States hospitals and found that medication errors increased 10% during the month of July at
teaching hospital
A teaching hospital is a hospital or medical centre that provides medical education and training to future and current health professionals. Teaching hospitals are almost always affiliated with one or more universities and are often co-locate ...
s, but not in neighboring hospitals.
["New residents linked to July medication errors"]
''amednews'', 21 June 2010, American Medical Association
The American Medical Association (AMA) is a professional association and lobbying group of physicians and medical students. Founded in 1847, it is headquartered in Chicago, Illinois. Membership was approximately 240,000 in 2016.
The AMA's stat ...
Surgical errors did not increase, leading to the hypothesis that medication errors are easier for new personnel to make because they are