Whether or not humor actually increases brain function is still up for debate. There is little research into the subject that determines either way. However, it is known that humor stimulates the parts of the brain that release the "feel good" chemical dopamine, which has been attributed to happier lives.
Laughter has been shown to boost the immune system by decreasing stress hormones and increasing immune cells and infection-fighting antibodies. Laughter also improves the function of the human cardiovascular system, increasing blood flow, which can help protect against heart attacks and other cardiovascular problems. Additionally, laughter relieves physical tension and stress.