We start laughing at the age of three and continue to laugh for the rest of our lives. However, the point is not in the great amount of reasons for laughing, the whole process has a deeper sense. Laughter is a serious matter, if it can be said so.
According to one of the numerous versions, laughter is a protective reaction of our body on the surplus of positive emotions. Hat is why happy people can laugh without any reason as their positive needs a constant outcome. On the contrary, those who are in a serious depression will find it hard to smile even if the circumstances are really funny.