What kind of medical problems can stress cause?!

I have had a person in the not so immediate family causing me stress. It all started when an email account of mine was hacked. The hacker used it to send emails for people to buy Viagra. The guy got irate because he thought I was insinuating he had a problem. I told him about the hacking. He did not believe me and insulted me. I have not been able to shake what he said and I think it is affecting my health. Is there any proof (links please) on what stress can do to you physically?