Negative friends may cause cancer: Study

Washington: Choose your friends wisely, they may make or break you, says an old adage. Now, scientists have backed it after finding link between toxic relationship and a host of illnesses such as cancer, depression and heart attack.

Researchers at the University of California Los Angeles found that negative social interactions can lead to increased inflammation, which may in turn cause a host of illnesses from cancer to heart disease and high blood pressure.

"We wanted to see how mental states such as optimism, or social relationships such as competition, get under the skin," study co-author Shelley Taylor, a social neuroscientist at the UCLA School of Medicine, was quoted as saying by ScienceNews.

For their study, published in the Proceedings of the National Academy of Sciences journal, Taylor and colleagues looked at the relationship between day-to-day stress and two proteins that trigger inflammation in the body, called pro-inflammatory cytokines.

The researchers asked 122 young, healthy adults to keep a diary of all positive and negative social interactions for eight days, as well as descriptions of any incidents that involved competition.

"We picked young adults with no history of heart disease or inflammation disorders or depression because we wanted to look at the biological processes in a population that was
healthy," Taylor said.

Several days later, they swabbed the volunteers` inner cheeks for fluid samples.

Analyses revealed that the people with the most negative social interactions recorded in their diaries, and those who reported stressful competition in work or academic pursuits,
had substantially higher levels of one of the inflammatory proteins, TNF receptor 2, than did those who recorded fewer such incidents.

People reporting stressful competition for another`s attention had high concentrations of the other inflammatory protein, interleukin-6.

The volunteers then underwent a stressful 25-minute test in which they did arithmetic calculations in their heads and gave a brief speech in front of strangers.

After this test, people who had had the most negative interactions earlier in the week again showed high levels of the inflammatory proteins.

The link between short-term stress and revved-up inflammation could have an evolutionary basis, said Nicolas Rohleder, a psychologist at Brandeis University in the US who wasn`t part of the study team.

"As early humans, we had to fight for our lives – fight or flight," he said.

Inflammation has a useful short-term role in fending off pathogens, so triggering inflammation as a response to stress may have been a way the body fended off infections caused by those encounters, which often resulted in some form of injury, he said. "Humans are not really running away now."

So reduced stress -- and therefore less inflammation -- may be one of the mechanisms that links social support with health outcomes, Taylor said. "Relationships are vital to health, like your diet," she added.