Don't worry, be happy and, according to new research, you will also be healthy.

It is estimated that over the course of one year, Americans suffer 1 billion colds. But new research shows that all it may take to avoid this common affliction（苦恼） is a positive and upbeat attitude. 

People who are energetic, happy and relaxed are less likely to catch a cold than those who are depressed, nervous or angry, finds a new study published in the journal Psychosomatic Medicine.

Healthy volunteers first underwent an emotional assessment in which they were asked to rate their tendency to experience positive and negative emotions--how often they felt pleased, relaxed, happy, or anxious, depressed and hostile. The subjects were next given a squirt（喷射） up the nose of a rhinovirus（鼻病毒）, the nasty little germ that causes colds.

Researchers then watched the volunteers to see who came down with a cold and waited to see how the unlucky ill manifested their cold symptoms.

"We found that people who regularly experience positive emotions, when exposed to rhinovirus, are relatively protected from developing illness," said Dr. Sheldon Cohen, lead author of the study and a psychology professor at Carnegie Mellon University.

Although positive people showed a greater resistance to colds, negative people did not necessarily get sick more often.

"Increases in positive emotional styles were linked with decreases in the rate of clinical colds, but a negative emotional style had no effect on whether or not people got sick," Cohen said.

So how can your emotions influence your health? In simple terms, when the brain is "happy" it sends messages to our organs that help keep the body healthy and sound.

"It's like a drug that is released by your state of mind and simply changing the state of mind can produce effects on the rest of the body through the nervous system and hormones," said Dr. Neil Shulman, associate professor of medicine at Emory University School of Medicine and author of Doc Hollywood. "Your chance of developing the common cold, pneumonia（肺炎）, or even cancer may very well be decreased by keeping your brain in a healthy state."

In addition, happy and relaxed people are prone to better health practices than their negative and stressed counterparts. They are more likely to get plenty of sleep and to engage in regular exercise, and have been shown to have lower levels of certain stress hormones.

Shulman says the study shows there are some simple things you can do to improve your chances of staying healthy.

"The take-home message is that we have very healthy ways that we can improve our overall well-being that don't cost money and that don't require a wait in the doctor's office," he said.