, I have 7 brothers and 4 of us have it now one has had for about 20 years I had it for 16 months another one got it about 4 months ago and the other 1 month ago , don't know what is causing it, don't know if parents had it they both have pass on already , do you think genetic , my t I believe was self induce listening to music on my tablet , they say it could go away don't know.