There is an old saying in English, "Laughter is the best medicine". Until recently, few people took the saying very seriously. Now, however, doctors have begun to study laughter and the effects it has on the human body. They have found evidence(证据) that laughter really can improve people's health.
Tests were carried out to study the effects of laughter on the body. People watched fun films while doctors checked their heart rate, blood pressure, breathing and muscles. It's found that laughter has similar effects to physical exercise. It increases blood pressure, the heart rate and the rate of breathing.
Other tests have shown that laughter appears to ease the pain on the body. In one experiment doctors make two groups of students listen to different radio programs. The group which could bear the pain for the longest time was the group which listened to a funny program. The reason why laughter can make pain less seems to be that it helps to produce endorphins(内啡肽)in the brain.
____, some doctors in the United States now hold laughter clinics(诊所), in which they try to improve their patients' condition by encouraging them to laugh. Even if their patients do not really feel like laughing, making them smile is enough to produce good effects similar to those caused by laughter.
