Is true tat laughing cause increase the life length????

I dont know if it scientifically proven that laughing makes you live longer or not, but in my opinion laughing can lengthen your life, because when you laugh, it means your happy, and when your happy your body is happy, and when your body is happy I believe that it doesnt stress and since it doesnt stress it helps you to live longer,because when you dont stress you dont age as fast as you do when you stress.Just like if your sad and you cry,I believe it makes your body sad,and when your body gets sad,it makes it over stress,and when you stress it makes your body age at a quick rate.So I believe that if you laugh you live longer,just like they say it takes less muscles to smile then it does to frown.