Anti-anxiety drugs may make you drowsy and impair your cognition in the short term, but taken appropriately there is no evidence that anti-depressants or anti-anxiety drugs will lower your intelligence. Anti-depressants may actually increase your I.Q. by a few points, since people who are very depressed tend to have decreased cognitive function.

If you take antidepressants they should not directly affect 'intelligence' per se. That will come and go with age regardless. The drugs just help control or make things 'better' for the short term for most people...if they are taken in the long term, the intelligence factor may still be there, but the behavior may not reflect it.

It doesnt really lower your intelligence but it slows it down. I have a friend who is taking anti depressant, and its kinda slowing his way of thinking.