Citation: http://www.straitstimes.com/BreakingNews/ANN/Story/STIStory_817340.html
What's the relation between his headache and watching porn videos?
In order to verify that porn videos caused his headache, the result should be compared with a result of his watching movies except porn videos.
But, this experiment hasn't already been done or isn't written on the article. So, I can't make sure that porn videos truly affect his health.
By the way, a picture on which a man watches a screen is shown on the article. On his glasses, a picture reflects. I wonder it is a screen of porn websites.
