In “Eleanor Rigby,” the Beatles ask, “All the lonely people, where do they all belong?” The answer may be: in a doctor’s office, according to scientists who studied the effect of isolation on people’s immune systems.

The research, led by scientists from the University of California, Los Angeles, School of Medicine supports past findings on increased mortality from cancer, infection, and heart disease among people without family ties or close friends. It is the first to trace the emotion to the genetic level using new tools that detect small variations in DNA.

Genes linked to immune-system inflammation were more active in six people who described themselves as lonely than in eight who said they had a normal social life, the study found. At the same time, DNA involved in systems that fight infection and spur disease-fighting proteins were less active. Identifying physical changes tied to social isolation opens new opportunities for care, the researchers said.

“If we can figure out the biology that puts these people at risk for death, we can protect Eleanor Rigby until she grows to a ripe old age,” an assistant professor at the university’s medical school and the author, Steven Cole, said, referring to the protagonist of the 1966 Beatles song.

“We may not be able to make her into a social butterfly, but we can keep her out of the coffin,” he said. Mr. Cole’s report, published yesterday in the journal Genome Biology, focuses on genetic influences on the body’s immune system, which creates antibodies and spurs controlled inflammation to fight foreign bacteria and viruses. The people studied weren’t “lonely as you are if you’ve just broken up with someone,” Mr. Cole said in a telephone interview. “Their loneliness is based on a general mistrust of other people.”

Participants for the study were selected from a group of 153 who scored the highest and lowest on a test designed to assess whether they were happy or felt lonely, and whether their feelings of social isolation were short-lived, or they felt it was a lifelong condition.

The genes that regulate inflammation in the lonely patients were overworking, meaning the body was inflamed when it didn’t need to be. Chronic inflammation is a major risk factor in heart disease, the researchers wrote.

The stress hormone cortisol, for instance, works to damp inflammation in the body. Cortisol was elevated so long among the people who categorized themselves as lonely that their bodies stopped responding to it, Mr. Cole said. That meant they didn’t have the ability to tamp down inflammation, he said.

“The body says, ‘Hey, cortisol’s been crying wolf for years,”‘ Mr. Cole said. “‘So when I see a lot of cortisol, I’m not going to inhibit it.”