There are some things about your health that you just can’t control: when your appendix bursts, or you accidentally step on a rusty nail or a stealth sea urchin pierces your foot on your summer vacation.

Trips to the hospital in the middle of summer are never fun. But are they perilous?

The July Effect is a well-known phenomenon in the medical world. Recent medical school graduates step foot in teaching hospitals as residents for the first time, as the class above them takes on new duties. “If you talk to anyone who works in a hospital … unequivocally they will tell you care is worse in July,” says Anupam Jena, an internist and assistant professor of health care policy at Harvard Medical School. “The interns know less than the physicians who were there two to three months before.”

Jena recalls his own days as a resident, when an intern gave a diabetic patient five times the amount of insulin the patient needed, and the next day, the patient’s blood sugar level fell to a dangerously low level. “The nurses picked up on it. Here’s a case of something that was potentially deadly, but there were safeguards in the hospital,” Jena says. “The patient only had diabetes and no other problems. Even with a potentially fatal medical error, this person was able to make it through.”

But even small mistakes could result in fatal errors in severely ill patients, Jena continues, so it’s those patients whom the July Effect could potentially affect. To that end, Jena conducted a study of heart attack patients in hospitals throughout the country, and found no mortality difference between patients at teaching and nonteaching hospitals in July. But in May, mortality was lower in teaching hospitals. “For every 100 people hospitalized with a severe heart attack, five more people will die in July than in May,” Jena says. While it’s hard to pinpoint the precise errors that make mortality rise, procedural delays may account for some: For example, even a half-hour delay in stenting – to open up clogged arteries – may be too late.

No July Effect on Less Sick Patients

But for “the everyday patient,” Jena continues, “There’s no July Effect.”

That was true for Robert West, professor emeritus of biochemistry and molecular biology at SUNY Upstate Medical University in Syracuse, New York. One morning at the beginning of July six years ago, West had chest pain. “I work at the medical school, so I walked down to the ER. They put me in a room, and they gave me morphine for pain. I started getting really hot,” West says. It turns out he was allergic to morphine – which neither he nor the interns could have known. He was given a medication to block the allergic reaction.

West also spent eight hours in the ER without being given anything to eat or drink. “It turned out to be a busy day. You could tell that a lot of students were really hesitant,” he says, adding that his wife eventually got him something to eat and drink at the vending machines.

Another thing West noted was the general chaos in the ER in July, as opposed to other months. “We have an underserved minority population that is constantly flowing into the ER,” he says. “This creates confusion, but you wouldn’t have as much confusion in April or May.”

Because of this experience, West says that he would try to avoid going to another teaching hospital in July. “If it was something that wasn’t really critical, you could postpone it until later,” he says.

Boot Camp for Newbie Residents

When the Annals of Internal Medicine ​came out with a paper in 2011 saying the July Effect was real, Diane Wayne​, the vice dean of education at Northwestern University Feinberg School of Medicine, decided to design a program to help incoming residents overcome their jitters and help prevent the July Effect.

The three-day course, which started in 2011 and won an innovation award from the Association of American Medical Colleges, gives students hands-on experience in basic medical procedures they're likely to encounter in the ER. The students actually have to perform the procedures on models before they can go into the hospital as residents. They also have to show they can read and interpret X-rays and electrocardiograms, and that they're armed with communication skills like talking to end-of-life patients about treatment options, Wayne says.

“You cannot practice your skills on patients,” she adds. “If you don’t think you know how to do it, then don’t do it. We are very interested in patient safety.”

The program also ensures that medical school graduates are starting their clinical experience on the same page, Wayne explains, since they’ve all come from different places and have varying levels of clinical experience.

Too Much Hype?

Still, some experts say the July Effect is all hype. “The overriding evidence is that the degree of problems that arise from [the July Effect] is relatively small,” says Kenneth Ludmerer , a professor of medicine and the history of medicine at Washington University in St. Louis. “The actual problem as opposed to the hype and anticipation is a reflection of one of the strengths [of the medical school system]: the supervision provided.”