I can't sleep regular hours. I'm up all night, sleep in snippets. Stressed, anxious, depressed, can't work. Can't do anything. It completely ruins a person.
It wont make you dumber, but it will make one wish they were dumb enough to be optimistic about what the future holds for one with tinnitus.
All of us are different. Tinnitus has not slowed me down at all. I have had to adjust my life and my habits, but I have not lost mental clarity due to it. I am still able to read books and focus even with the demon level ringing... that I live with every second of my life. Does it take patience, practice? yes, it does, but it is very doable....
I think that the answer depends on what is meant by "making us dumber".
This noise torture (for some of us) can cause tremendous anguish, insomnia, unimaginable stress, and difficulty concentrating. These things are known to inhibit intellectual capacities while they are happening. But, does tinnitus itself actually affect your neurons etc. in such a way as to directly lower your IQ? AFAIK there is no evidence for such a thing.