The viruses that cause the common cold are always lurking. But consider this: Even if we touch a doorknob or keyboard that's covered in cold germs from an infected person, we don't always catch the cold.

"Sometimes when we're exposed to viruses, we end up not getting sick," says Aric Prather, a psychologist at the University of California, San Francisco, who studies how our behaviors can influence our health.

Our immune systems often fend off the viruses that cause colds. But,how well our bodies mount this defense can vary.

"There's evidence that people who don't get enough sleep show higher levels of inflammation," says Sheldon Cohen, a psychologist at Carnegie Mellon University who's been studying the common cold for decades and co-authored the study.

Other factors and behaviors may increase susceptibility too, research suggests. For instance, age may play a role, and smoking, chronic stress and a lack of exercise can all make us more susceptible. - Read More at NPR

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