Priya Joshi isn't sure when exactly the shift happened, when the thrill of graduating from medical school was replaced with the anticipation and anxiety of starting her residency.

 "I am absolutely very nervous right now," she says, describing herself as "easily a twenty" on a scale of one to ten.

Nervous, but excited. Sure, Joshi has been on hospital rotations before, but the focus then was on learning, on getting a good grade. Now she'll be Doctor Joshi.

"Tomorrow I will be directly doing everything I can for the patient," she says. "And if I impress the residents, that's great, but hopefully the biggest part for me tomorrow is to get through the day and actually help people well on my own."

It's a big moment for Joshi and the some 30,000 other first year residents who are starting their first jobs as doctors this summer, but it's also a big moment for hospital staff, who've been bracing for the onset.

"It is stressful and overwhelming because, you know, we're receiving a whole bunch of new folks at once," says Dr. John Q. Young, a psychiatrist and residency training director at Hofstra North Shore-LIJ School of Medicine in New York. "We're having to orient and train them, and make sure they're adequately prepared to assume their new roles."

Is it a bad time to go to the hospital?

What unites both Young and Joshi is their deep concern for patients' well-being, but given this disruption and drop in experience in July, how does that impact care at teaching hospitals? Does patient safety decrease?

Young likens this kind of turnover to what might happen if a quarter of a sports teams' members were subbed out for rookies during an important game. And as new residents like Joshi come in, others move up and assume more responsibility. Senior residents move on. The 'quarterback' so to speak, or attending physician, remains the same.

The notion that care worsens during this time has long been referred to as "the July effect."

"I've been working now in medicine for well over 30 years, and I've heard about it every year since I first started," says James B.Young, head of one of the largest internal residency programs in the country at the Cleveland Clinic in Ohio.

In Great Britain, the time when residents traditionally join the ranks each August has been notoriously nicknamed "the August killing season."

Many in health care have been pondering whether this phenomenon is urban myth or reality for years. The answer, as found in hundreds of studies, paints a complicated picture.

Some large studies point to a 'July Effect'

One of the most comprehensive looks at the July effect comes from Dr. John Q. Young, the psychiatrist at Hofstra, who identified some elements of an impact on patient death rates and length of hospital stays.

In 2011, Young led a systemic review of all the research done over the last two decades on the so called July Effect. Some studies found an effect for certain measures, some didn't. Studies analyzing medical errors were especially weak.

But when he focused on the better studies, the ones with larger sample sizes, the ones that compared similar types of patients in the same month, "overall in total, there seemed to be a signal where patient mortality goes up in July and the efficiency of care goes down."

The relative risk of death was anywhere from 4 to 12 percent higher at teaching hospitals during that time. It's important to note that mortality rates in July are lower across the board, compared to winter months.

Safeguards challenge notion of a big effect

Meanwhile, Dr. James B. Young over at the Cleveland Clinic doesn't buy that the July Effect exists, at least anymore.

"It's probably more myth than reality," he says, pointing to a 2013 study that found no differences in outcomes among back surgery patients in July. And he says teaching hospitals have undergone major changes in recent years to include more safeguards for residents.

"They're not working in a vacuum," he says. "They're supervised."

Residents' responsibilities increase in stages, based on experience and performance. They get very little autonomy at first and also must go through orientation, practice scenarios and role plays.

"This isn't like you get a group of people and tell them, 'Ok, go out and take care of ten patients, and do these 200 tasks, and I'll talk to you tomorrow,'" says Dr. Lisa Bellini, who oversees the University of Pennsylvania's residency program for internal medicine.

Tazo Inui just completed his surgical residency at University of California San Diego. He says if anything, doctors and staff are even more careful, more watchful in July.

"From my own experience, I was probably as safe then or safer than any other time because I was afraid to do things like prescribe Tylenol, and so I'd ask permission for everything," he recalls.

Theresa Brown, a Pittsburgh-based nurse of seven years who writes about health care, says mistakes are bound to happen, even if robust evidence doesn't back it. Residents must undergo a huge learning curve.

"Just because the data is inconclusive doesn't mean that it's not a problem," she says. "It's not like you've got an intern [who] will say order a killing dose of [an] inappropriate drug, sort of complete incompetence and malpractice, I haven't seen that, but it's these little things that can accumulate, and for nurses it's very stressful."

It can be a challenge for everyone, finding that right balance of working as a new team. Brown, who until recently worked on an oncology unit, recalls one time when a patient was nearing death and in a lot of pain. The new resident wouldn't up the medicine.

"You know, it's not that that's a bad impulse necessarily, but it was the wrong choice absolutely in this situation," she says. "I ended up going over his head and calling in a palliative care doctor because they had been consulted earlier."

Patient safety an increasing priority

15 years ago a report from the Institute of Medicine shook health care, highlighting there may be as many as 100,000 patient deaths annually in hospitals of all kinds due to medical errors. It spurred a major push to improve patient safety, says Dr. Thomas Nasca, head of the main accrediting agency for residency programs and a former dean at Thomas Jefferson University's medical school.

"Hospitals in the learning environment have made progressive improvement in safety and quality, but it is not where we want it to be yet," he says.

Nasca says those in medicine now recognizes that injuries due to errors in hospitals - teaching and non-teaching - are a big problem, but residency education can have a major role in shaping physicians' attitudes and behaviors about safety and quality.

This increasing recognition has led to new evaluation standards, more attention to fatigue and rules to cap work hours. It's too soon to know the most effective approach, but Nasca says one continuing challenge is how to create smoother patient transitions as residents assume shorter shifts.

And beyond learning to take on a greater role in treating patients, residents are also having to acclimate to each hospital units' systems of care, including everything from medical records to discharge procedures.  

But as for whether patients might want to think twice about going to the hospital this month, Dr. John Q. Young at Hofstra, who found evidence of some aspect of a July Effect in his 2011 research review, gives no pause.

"You should not delay the care you need," he says.

He does have this advice for those who might be worried. Bring a family member or friend who can help advocate. And remember, even though newer doctors may be on staff, they're working under senior staff members.

"You can always ask to talk with the more experienced physician or the attending who's directing the care," he says.

Debrief after day one

After finishing her first day as a resident in Philadelphia , Priya Joshi is upbeat.

"I thought this was going to be in some fashion embarrassing, flustering or traumatic," she says. "And it was for the most part very, very nice and supportive."

Joshi, who's on a primary care track, says she had two levels of supervision. Senior residents walked her through everything.

The significance of her new role, though, really hit home mid-day.

"There was this one moment in the day where this one patient was talking on his phone and he paused and said, 'hold on a minute, I'm talking to my doctor.' I'm looking at him and wondering, who are you talking about? And realized it was me!" she recalls. "It felt really humbling. Maybe that's the moment I'm going to look back on and think, 'Yeah I'm a doctor, and I'm here to take care of someone.' And it's nice to take on the responsibility and the weight of what that means to that person."

When asked if she worries she'll ever make a mistake or harm a patient, Joshi says the fear is there.

"There's a level of, 'now it's on me.'"

She's a perfectionist and wants to be prepared for any scenario.

But she knows that's impossible.

That's why she says she vows to recognize when she is unsure to ask for help, and then use those experiences to learn and become even better at caring for her patients now and in the future.