For 10 years, Nora Volkow has been the director of the National Institute on Drug Abuse, overseeing a budget of nearly $1 billion and much of the world’s research on one of medicine’s most controversial subjects. It isn’t surprising that she has her critics.

What is more revealing is the one point that none of them dispute.

“She is a brilliant scientist,” said Mark Kleiman, a public policy professor at the University of California at Los Angeles.

Volkow’s work has shown that sustained drug use can result in lasting physical ­changes to the structure of the brain. Other researchers have praised her for helping to establish addiction as a topic worthy of rigorous scientific study, elevating drug use above the realm of emotions and moral judgments and onto the more tranquil plane of data and objectivity.

“Let’s face it: People with addictions do bad things,” said Thomas McLellan, a friend of Volkow’s and a former senior drug official in the Obama administration. “Nora’s work has shown that they’re bad because the brain structures and functions that are specifically targeted by abuse screw up motivation, reward and learning.”

Nora Volkow (Mary Noble Ours/Courtesy of the National Institute on Drug Abuse)

For her work, Volkow has been named to the National Academy of Sciences, and she has recently been nominated for a Samuel J. Heyman medal for excellence in civil service. The winners of the Heyman medal will be announced in October.

As NIDA director, Volkow has supervised funding for research into the genetic factors affecting drug use, as well as work on vaccines that researchers hope could prevent drugs from entering the brain.

Yet competition for the institute’s resources, reduced as a result of the federal sequester, is intense. Four in five applications for grants are rejected. Kleiman and others argued that while NIDA supports fascinating and groundbreaking research, Volkow’s agency neglects practical, unglamorous solutions that could help addicts more quickly.

“She’s going to find the drug that cures [cocaine] addiction and get a Nobel Prize for it,” Kleiman said, referring to Volkow. “Everything about NIDA has been distorted to that end.”

Volkow, who declined to be interviewed for this article, lives in Bethesda with her husband, National Cancer Institute physicist Stephen Adler. Colleagues described her as an energetic and tireless administrator who travels constantly for speaking engagements and runs daily.

She established her reputation as a neuroscientist at Brookhaven National Laboratory in Upton, N.Y. Before that, she studied medicine at the National Autonomous University of Mexico, not far from where she grew up.

Volkow’s childhood home in Mexico City was an unusual one. Her great-grandfather was Leon Trotsky, the Soviet military leader and prominent Marxist whom Joseph Stalin expelled from Russia in 1929. Trotsky eventually moved to a villa on the outskirts of the Mexican capital, but he was not safe there.

In 1940, a Stalin agent hoodwinked Trotsky into meeting privately with him, saying he wanted to discuss an article on French economic statistics. Alone with Trotsky in his study, the assassin cracked open the aging revolutionary’s skull with the broad edge of an ice ax.

Trotsky did not survive the attack, but his family remained in the villa, and Volkow grew up there. She told CBS News’ “60 Minutes” last year that as a child, she was afraid to go into the study at night. “Something remains there,” she said.

“Ghosts, in a way,” said the interviewer, Morley Safer.

Neuroscientists don’t believe in ghosts. She corrected him. “Ghosts in our brain,” she said.

Volkow is always talking about her brain, according to McLellan. “She will say, ‘My brain really wants chocolate now,’ ” he said. “I say, ‘Am I talking to Nora, or am I talking to her brain?’ . . . It’s how she understands the world.”

Her fascination has produced important insights into addiction. Sustained drug use alters what addicts find pleasurable and rewarding, making it less likely that addicts will resist the urge to get high. Volkow has shown that ­changes in the brain can last through many months of abstinence, forcing clinicians to think more carefully about helping recovering addicts stay clean in the long term.

Treatments for addicts generally involve therapy and counseling. Opiate and heroin addicts can take medications such as methadone, but for most addictions, effective pharmaceutical remedies are lacking.

“A cure would be fantastic, and that means you get a medication like an antibiotic, I cure you,” Volkow told “60 Minutes,” describing her hopes for the field. “We’re not there yet, but perhaps one day, we may be. In my brain,” she added, as though that organ embodied her entire worldview on scientific progress, “if you don’t dare to think very ambitious things, you’ll never be there.”

One promising area of research involves anti-drug vaccines. The idea is to train the immune system to neutralize a drug with the proteins known as antibodies, which the body uses during an infection to mark invaders for destruction. Attached to these large molecules, the drugs would be unable to slip out of the bloodstream and into the brain.

It could be a long time before such vaccines are ready for general use. They wouldn’t provide lifetime immunity, researchers said, nor would they cure addiction in the same way that an antibiotic cures conjunctivitis. Addicts would receive vaccines along with other medications and counseling.

Only 13 percent of NIDA’s research budget last year was allocated to pharmaceutical treatments such as vaccines. But for the institute’s critics, the emphasis on finding a cure reveals flaws in the approach of the institute, and of the broader medical establishment, to drug research.

NIDA officially defines drug addiction as a “chronic, relapsing brain disease.” Volkow didn’t formulate that definition, but she has been one of its most visible proponents. Although the definition is widely accepted, a small but vocal group argues that the definition is too narrow to describe such a complicated condition.

“If you’re a clinician or a policymaker, construing addiction as a brain disease is not necessarily the most useful way to understand it. It overlooks the social and psychological dimensions,” said Sally Satel, a psychiatrist affiliated with the American Enterprise Institute.

Satel and others argued that NIDA and the external reviewers who evaluate grant applications have ignored more immediately useful projects less directly connected to medical practice.

UCLA’s Kleiman has published research on a probation program in Hawaii, called Project HOPE, that has shown remarkable success in helping methamphetamine addicts quit without counseling or medication. The concept is simple: Every violation is punished immediately by a few days in jail.

NIDA has rejected applications to study the program in more detail. Those familiar with Project HOPE say the research establishment has yet to confront the implication that something as simple as a few days in jail can lead even hardened drug users to stay clean.

NIDA does support other work on therapies and treatments for criminals. “Significant advances in promoting effective, science-based drug abuse prevention and treatment within the criminal justice system is one of our proudest achievements over the past decade,” Wilson Compton, the director of NIDA’s division for epidemiology, services and prevention, said in a statement.

Angela Hawken, a professor at the Pepperdine University School of Public Policy, hopes the institute’s portfolio will soon include Project HOPE. After collaborating with Kleiman to study the Hawaii program, Hawken turned to NIDA for additional funding. Although her applications were rejected in what she called a rigorous but fair review process, the institute recently asked her to submit a new proposal.

“I think the field is changing,” she said.

Proponents of the theory of addiction as a brain disease concede that there are other important factors besides brain damage in recovery, including the decisions the addict makes. In other words, addicts can choose not to use drugs if they’re worried about going to jail for a few days, but the choice is a harder one.

That mysterious capacity for choice apparently explains why one person gets hooked in the first place and why another manages to quit. Like the presence that kept Volkow out of her great-grandfather’s study at night, it’s something in the brain that neuroscience hasn’t yet been able to account for.