Patients who cannot connect with their doctors may not get the best possible treatment.
"It is our responsibility, as treating physicians, to respect their vulnerability as much as their privacy. Our dress and demeanor must reflect this caring," said Dr. Nortin Hadler, author of "The Last Well Person."
A 2005 American Medical Journal study concluded that patients overwhelmingly preferred physicians in professional attire with a white coat.
Researchers asked roughly 400 patients and visitors in a hospital waiting room to look at pictures of doctors, all dressed differently, and to state their preferences on physician attire, as well as their trust and willingness to discuss sensitive issues.
The results were clear and still hold true one year later.
"When we deny [patients] that comfort -- because they are offended by our mode of dress or behavior -- we are not giving them our best," said Dr. Cliff Saper, chairman of the department of neurology at Beth Israel Deaconess Medical Center in Boston.
The question of whether doctors should be allowed to dress freely still isn't a straightforward one.
Doctors are typically strong-willed, independent thinkers. How else could they have gotten through med school?
Clothing restrictions in such a demanding profession may feel unjust to some, particularly because recommendations differ across genders.
"I remember [my husband] complaining how unfair it was that I could just throw on slacks and a sweater while he had to fuss with a shirt, slacks and tie," said Jeannette Byers, who attended medical school alongside her husband.
Byers is now an emergency-room physician at Hackley Hospital in Muskegon, Mich.
One doctor recalled her own experience as a budding clinician.
"I was a med student in the '70s, when students argued that professionalism and competence would trump our patients' reactions to our long hair -- women and men -- men's facial hair, and sometimes casual dress," said Dr. Paula Hillard, a professor of obstetrics and gynecology and of pediatrics at the Cincinnati Children's Hospital Medical Center.
"We bridled at any suggestions that we were any less effective as clinicians. Fast-forward to today -- students make the same arguments that their piercings, midriff-baring [outfits] and tattoos do not undermine their credibility or abilities."
But patients may argue that a doctor's ability to express himself or herself as an independent thinker does not trump a patient's comfort level.
"If I go to the ER, and the doctor walks in with a Hawaiian shirt and shorts, with long hair in a ponytail, then I feel very uncomfortable," said Jennifer Sanders, a patient from Fairfield, Mich.
Casual dress is OK in some places. But some hospitals have very strict dress codes. Many hospitals have their own dress codes that allow doctors to forego ties, for example, but that forbid open-toe shoes.
"Mayo Clinic does have a strong dress and decorum policy. Essentially it is coat and tie for men and appropriate equivalent business attire for women, both in the administrative staff and among physicians," said Lee Aase, media relations for the Mayor Clinic.
The Mayo Clinic believes attire and patient confidence are connected.
"We do not do 'Casual Fridays' or other exceptions. We see dress and decorum as a symbol of professionalism and of respect for patients and their families," Aase said.