Last week DISCOVER brought you the sad and somewhat counter-intuitive study that suggested loneliness could actually be "contagious" and spread across a social network. Now more bad news for the lonely. In a study (in press) in the Proceedings of the National Academy of Sciences, another team of researchers argues that, in rats at least, loneliness can increase cancer incidence. The scientists separated their test rats at birth, keeping them either in groups of five or alone.
Those kept alone had a 135% increase in the number of mammary tumours, a 8,391% increase in the size of tumours and a 3.3-fold increase in the relative risk of malignancy [Nature News]
. They also showed higher levels of the hormone corticosterone, which is connected to stress. The researchers note that these early findings were done with just 40 rats in total. And the connection of stress and breast cancer can't yet be translated to humans, says researcher Ed Yong.
"But it's possible that stressful situations could indirectly affect the risk of cancer by making people more likely to take up unhealthy behaviours that increase their risk, such as overeating, heavy drinking, or smoking" [BBC News]
. Indeed, the stress from being alone is the main suspect in these normally social Norway rats' increased cancer risk, lead researcher Gretchen Hermes says, and scientists have seen the detrimental health effects that badly managed stress can have on people.
"The effects are equal to or greater than the effects of cigarette smoking—that includes a significantly shortened life span" [ABC News]
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