Can smoking cannabis regularly make you dumb long term?

One of the proven true impacts of smoking dope in more then a causal recreational type use.

If you take up the habit before your brain is fully developed it can have some longterm consequences. 

"Dumb"? Not exactly a technical term, but chronic use can lead to diminished mental capacity, yes.

no and stop beliving everything you see on the media

I've seen lifelong pot smokers that are very sharp, and some seem very slow .... I can only conclude that they would be the same with or without pot