Dr. Robert Ader, an experimental psychologist who was among the first scientists to show how mental processes influence the body's immune system, a finding that changed modern medicine, died on Tuesday in Pittsford, N.Y. He was 79.
His death followed a long illness and complications of a fracture suffered in a fall, his daughter Deborah Ader said.
Dr. Ader, who spent his entire career as a professor of psychiatry and psychology at the University of Rochester School of Medicine and Dentistry, conducted some of the original experiments in a field he named himself, psychoneuroimmunology.
His initial research, in the 1970s, became a touchstone for studies that have since mapped the vast communications network among immune cells, hormones and neurotransmitters. It introduced a field of research that nailed down the science behind notions once considered magical thinking: that meditation helps reduce arterial plaque; that social bonds improve cancer survival; that people under stress catch more colds; and that placebos work not only on the human mind but also on supposedly insentient cells.
At the core of Dr. Ader's breakthrough research was an insight already obvious to any grandmother who ever said, "Stop worrying or you'll make yourself sick." He demonstrated scientifically that stress worsens illness — sometimes even triggering it — and that reducing stress is essential to health care.
That idea, now widely accepted among medical researchers, contradicted a previous principle of biochemistry, which said that the immune system was autonomous. As late as 1985, the idea of a connection between the brain and the immune system was dismissed in an editorial in The New England Journal of Medicine as "folklore."
"Today there is not a physician in the country who does not accept the science Bob Ader set in motion," said Dr. Bruce Rabin, founder of the Brain, Behavior and Immunity Center at the University of Pittsburgh Medical Center, who considered Dr. Ader a mentor. "He attracted interest in the field and made it possible to prove that 'mind-body' is real."
Dr. Ader said his breakthrough began in 1975 with what he called "scientific serendipity."
He and a fellow researcher, Dr. Nicholas Cohen, were conducting an unrelated experiment about taste aversion involving rats and saccharine-sweetened water when they stumbled on a mysterious phenomenon.
In the experiment, one group of rats was given sweetened water accompanied by an injection that caused stomach aches. (A control group got only the sweetened water.) When the injections stopped, and the rats that had experienced stomach aches refused to drink the water, researchers force-fed them with eye-droppers in order to complete the experiment's protocols.
Dr. Ader and Dr. Cohen had expected the conditioned rats to refuse the drink. They had not anticipated that forcing them to drink would eventually kill them, however, which it did, some time afterward.
The two reviewed their protocols and guessed that the drugs used in the injections might have had some bearing on the deaths. They could have used any drug that caused stomach pain without doing serious harm. But the researchers discovered that they had unwittingly picked Cytoxan, which besides causing stomach aches suppresses the immune system. At first they suspected that the rats had died from an overdose of Cytoxan. Then they determined that the dosage the rats received had been too low to support that explanation.
So they developed a theory, which became a landmark of medical science as further experiments proved it correct: The rats died because the mere taste of saccharine-laced water was enough to trigger neurological signals that did indeed suppress their immune systems — exactly as if they had been overdosed with Cytoxan. The rats succumbed to bacterial and viral infections they were unable to fight off. It was an example of the so-called placebo effect, only in this case it did not fool the brain into thinking it had been given something beneficial but rather the opposite.
The findings were "incontrovertible," Anne Harrington, a Harvard professor of the history of science, wrote in the 1997 book "The Placebo Effect."
"The fact that he had achieved this in rats rather than humans was a further blockbuster," she continued, "because it undermined the frequent assumption that placebo effects were a product of peculiarly human interpersonal processes."
Robert Ader was born on Feb. 20, 1932, in the Bronx, the older of two sons of Mae and Nathan Ader. His father, who owned a liquor wholesale company, died in a car accident in 1945 when Robert was a teenager. After graduating from the private Horace Mann School in the Riverdale section of the Bronx, he received his bachelor's degree from Tulane University and, in 1957, his Ph.D. in psychology from Cornell.
Soon after, he became an assistant professor in the department of psychology at the University of Rochester, where he went on to hold many teaching and research posts. He retired in July as a professor emeritus of psychosocial medicine.
Besides his daughter Deborah, he is survived by his wife, Gayle; three other daughters, Janet, Rini and Leslie Ader; and a grandson.
Since he inaugurated the study of psychoneuroimmunology (usually referred to as PNI), Dr. Ader had to defend its premise against doubters in the medical establishment and later to disassociate it from New Age therapies that he called "flaky" because they had not been grounded in solid scientific experimentation.
Deborah Ader, a psychology researcher, said a sense of modesty had been at the core of her father's curiosity as a scientist.
"My father used to say, 'I just didn't know any better,' " she said, recounting how he had described his pioneering research.
He told her, she recalled, "I didn't know the immune system wasn't supposed to be connected to the brain."
