Not really. It's really only a threat that parents use to make their kids do something different. It does depend what you watch. I mean, Tellytubbies could rot the brain of anyone, but things like the news and documentaries are very healthy and informative. It keeps your brain busy, if anything, but I don't believe it rots your brain.
It's possible to be geriatric with senile dementia at 24 years old for all those couch potatoes. From leaving school with no ambition or self hope, then died at 25 yr old. Why be addicted to soap operas? we've got our own lives to lead.