http://nymag.com/scienceofus/2014/12/hugs-were-the-cure-for-the-common-cold-all-along.html
“We know that people experiencing ongoing conflicts with others are less able to fight off cold viruses. We also know that people who report having social support are partly protected from the effects of stress on psychological states, such as depression and anxiety,” said Cohen in the release accompanying the new paper, which will be published in an upcoming issue of Psychological Science.