My 5 year old has a laughing tick

For the past 8 months or so my son has had a verbal tick. It's just a little short chuckle like you might make after someone said a dumb pun. Initially he would do it and we would say "whats funny" and he would tell us "nothing". Eventually he told my wife that it was "like a cough" and he had to do it.My wife and I have talked to the pediatrician about it and she basically said that he will more than likely grow out of it. What scares me is that my little brother has been diagnosed as OCD and has had some seriously weird behavioral stuff in the past. He seriously only wore one shirt for like 2 years....every single day. He is pretty "normal" these days but knowing that is in my genes scares me.At this point my wife and I just pretend it doesn't happen but the frequency is weird, she is convinced that it's tied to stress, I'm not. The other day he and I were swimming and he was having a blast but he would go under, come up for air, make the noise and go back down.I'm really at a loss, any advice would be great. via /r/Parenting http://ift.tt/2au5i2D