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.
In our slideshow this fall of social factors that make you fat, DISCOVER mentioned research from 2007 that gathered data from the famous Framingham Heart Study, which has been tracking people in the Massachusetts town since 1948, to show that having overweight friends made people more likely to put on the pounds. Now, another study, this time published in the Journal of Personality and Social Psychology, uses the same Framingham data to suggest that loneliness is actually contagious.
But how could the feeling of social isolation be socially contagious? The federally funded analysis of data collected from more than 4,000 people over 10 years found that lonely people increase the chances that someone they know will start to feel alone, and that the solitary feeling can spread one more degree of separation, causing a friend of a friend or even the sibling of a friend to feel desolate [Washington Post]. Friends of lonely people were 52 percent more likely to develop lonely feelings, the researchers say, and a friend of that person was 25 percent more likely.