My 27 yrs old son is working 17-18 hrs, six days a week. do you think it is really effecting his health in a harm way?

Hard to say...: Without an examination, no one can say how healthy he is or isn't. He's not getting much sleep, his social life is non-existent, and i'm sure he's tired. I admire his dedication.. Very few people work that much, so he must be making a good living. Family? Expenses? Don't know the reason for the long hours or the type of work, which would factor into any comment.

unlikely: You are lucky , your son is motivated hard working 27 old young man , will slow down when he reaches his goal , don't worry help him reach it and let him grow.