Mary Jeanne Kreek, who studied addictive diseases at the Rockefeller University for more than 50 years, died on March 27 at the age of 84. Her work helped uncover the biology behind addiction and, most notably, led to the successful treatment of heroin addiction with methadone.

“She was a wonderful scientist who made groundbreaking contributions to the field of addiction medicine and to social equity in a way that was before her time,” Sarah Schlesinger, a cellular immunologist and physician at the Rockefeller University, tells The Scientist. Kreek championed the idea that people addicted to drugs should be treated with dignity, not stigmatized, Schlesinger adds. “[She saw] the problems of drug use as a genetic disease to which people had a predilection and needed to be treated for, long before that was a common idea. She was a real pioneer in that way.”

Born in Washington, DC, in 1937, Kreek attended Wellesley College for her bachelor’s degree and earned her MD from Columbia University College of Physicians and Surgeons in 1962, according to an obituary. After a residency at what is now Weill Cornell Medicine, she and psychiatrist Marie Nyswander joined Vincent Dole’s lab at Rockefeller in 1964 to develop addiction treatments. In a landmark 1966 paper, the researchers showed that heroin addiction could be treated with methadone, a groundbreaking treatment that is still used today.

“The most important thing that [the] three of us conceptualised was that addiction was a disease, a disease of the brain that had behavioural manifestations, and not criminal behaviour,” Kreek said in a 2006 obituary for Dole.

Throughout her career, Kreek sought to understand the biological basis of addiction. She identified genes that make some people more predisposed to addiction and was among the first to identify specific genes whose expression was altered by drug use, leading to neurochemical and behavioral changes. Her work helped develop new ways to recognize and treat drug addictions, the obituary notes.

“Mary Jeanne was a giant in bidirectional translational research, bringing the most rigorous science to improving the lives of millions of individuals who were marginalized by society, and even by much of the medical community,” says Barry Coller, the physician-in-chief of the Rockefeller University Hospital, in the obituary.

Kreek is also known for her mentorship and support of young scientists. “She was tremendously supportive of other women in science and medicine,” says Schlesinger. “She was brilliant and demanded the most of herself and demanded a lot of everybody around her, but along with that she was very generous. . . . She was a source of inspiration and direct mentorship to women in her field and outside.”

A devoted mother and grandmother, Kreek was very supportive of her colleagues’ and students’ families, says Schlesinger. “She was tremendously generous to others, both male and female, about time off to take care of their children and about bringing their children to the lab. Now that seems more normal, but at the time, that was unusual and really groundbreaking.”

Kreek maintained an active research program right up until her death. “Mary Jeanne was never going to retire. She was very clear about that,” laughs Schlesinger. “She called it the ‘R’ word and she wasn’t having it.”

According to the obituary, Kreek is survived by her son and daughter, their spouses, and four grandchildren. Her husband of 48 years, Robert Schaefer, Sr., a gastroenterologist at Weill Cornell Medicine, died in 2018.