The U.S. surgeon general’s office estimates that more than 20 million people have a substance use disorder. Meanwhile, the nation’s drug overdose crisis shows no sign of slowing.

Yet, by all accounts, there aren’t nearly enough physicians who specialize in treating addiction — doctors with extensive clinical training who are board-certified in addiction medicine.

The opioid epidemic has made this doctor deficit painfully apparent. And it’s spurring medical institutions around the country to create fellowships for aspiring doctors who want to treat substance use disorder with the same precision and science as other diseases.

Now numbering more than 60, these fellowship programs offer physicians a year or two of postgraduate training in clinics and hospitals where they learn evidence-based approaches for treating addiction.

Such programs are drawing a talented new generation of doctors and idealists, such as Hillary Tamar.

Tamar, now in the second year of a family medicine residency in Phoenix, wasn’t thinking about addiction medicine when she started medical school in Chicago.

“As a medical student, honestly, you do your ER rotation, people label a patient as ‘pain-seeking,’ and it’s bad,” she said. “And that’s all you do about it.”

But in her fourth year of med school, Tamar was assigned to do a rotation at a rehab facility in southern Arizona.

“I was able to connect with people in a way that I haven’t been able to connect with them in another specialty,” the 28-year-old recalled.

Working with patients there transformed Tamar’s understanding of addiction, she said, and showed her the potential for doctors to change lives.

Patients, she said, “can go from spending all their time pursuing the acquisition of a substance to being brothers, sisters, daughters [and] fathers making breakfast for their kids again.

“It’s really powerful.”

When Tamar finishes her residency, she plans to pursue a fellowship in addiction medicine. She sees addiction medicine, like primary care, as a way to build lasting relationships with patients — and a way to focus on more than a single diagnosis.

“I love when I see addiction patients on my schedule, even if they’re pregnant and on meth,” she said. “More room to do good; it’s exciting.”

Doctors with Tamar’s enthusiasm are sorely needed, said Anna Lembke, medical director of addiction medicine at Stanford University School of Medicine and a longtime researcher in the field.

“Even 10 years ago,” Lembke said, “I couldn’t find a medical student or resident interested in learning about addiction medicine if I looked under a rock. They were just not out there.”

But Lembke sees a change in the upcoming generation of doctors drawn to the field because they care about social justice.

“I now have medical students and residents knocking on my door, emailing me,” she said. “They all want to learn more about addiction.”

Historically, the path to addiction medicine was through psychiatry.

That model started to change in 2015, when the American Board of Medical Specialties — considered the gold standard in physician certification in the U.S. — recognized addiction medicine as a bona fide subspecialty and opened up the training to physicians from other medical fields.

Until then, Lembke said, there had been no way to get addiction fellowships approved through the nationally recognized Accreditation Council for Graduate Medical Education. And that made recruiting young talent — and securing funding for their fellowships — difficult.

Last year, the council began accrediting its first batch of addiction medicine fellowship programs.

“We have an enormous gap between the need and the doctors available to provide that treatment,” Lembke said.

“At least the medical community has begun to wake up,” she added, “to consider not only their role in triggering this opioid epidemic, but also the ways they need to step up to solve the problem.”

When Luke Peterson finished his residency in family medicine in Phoenix in 2016, there were no addiction medicine fellowships in Arizona.

So he moved to Seattle to complete a yearlong fellowship at Swedish Cherry Hill Family Medicine Residency. There he learned, among other things, how to treat pregnant women who were in recovery from drug use.

“I really needed to do a fellowship if I was going to make an impact and be able to teach others to make the same impact,” said Peterson, who went on to help found an addiction medicine fellowship program in Arizona. His program is based in Phoenix at the University of Arizona’s medical school and its teaching hospital.

Arizona’s two addiction medicine fellowships received council accreditation last year — a stamp of approval that made the programs desirable choices for up-and-coming physicians, Peterson said.

Not every doctor who plans to treat substance use disorder needs to do a fellowship, he said. In fact, his goal is to integrate addiction medicine into primary care settings.

But a specialist can serve as a referral center and resource hub for community doctors. For example, a specialist like Peterson can teach physicians how to provide medication-assisted treatment such as buprenorphine.

Public health leaders have been pushing to get more physicians trained in evidence-based treatment like buprenorphine, which has been shown to reduce the risk of death among people who have recovered from an opioid overdose.

“As we provide more education and more support to primary care physicians,” Peterson said, “they will feel more comfortable screening and treating for addiction.”

Peterson’s own journey into addiction medicine began during a rotation with a family doctor in rural Illinois.

“In moments that most doctors find uncomfortable — maybe a patient comes in to request pain medication and you’re seeing the negative side effects — he did not shy away from that situation,” Peterson said. “He addressed it head-on.”

It was a formative experience for Peterson — one he wants other young doctors to have. And he recognizes the urgency.

“In 20 or 30 years from now,” Peterson said, “those medical students are going to look back at my current generation of doctors, and we will be judged by how we responded to this epidemic,” in the same way he and his peers now look back at how doctors handled the HIV epidemic.

One of the first steps in stopping this epidemic, he said, is making sure there are enough doctors who know how to respond.

Many of today’s medical students, such as Michelle Peterson — who is not related to Luke — say they feel the calling, too.

She’s in her first year at the University of Arizona College of Medicine and became interested in specializing in addiction after working at an outpatient treatment center.

She said she was already learning about addiction in her classes, hearing from doctors in the field and seeing other classmates equally engaged.

“It’s definitely not just me,” she said. “There are quite a few people here really interested in addiction.”

It’s a trend she and her mentors hope will continue.

Stone writes for Kaiser Health News.