Have you tried googling? The surveys and studies are out there.
I've seen more than a few, but none of them demonstrate that becoming a theist reduces your IQ. None have proven that becoming an atheist increases your IQ. There's no substantial correlation that can be drawn here, other than that most atheists are single white males and that IQ tests are slanted in their favor. Please, if you have a definitive study I've managed to overlook, trot it out. It's not my duty to present your evidence for you. If you say the evidence exists, then the onus is on you to produce it.
The only evidence presented by
@psychoslice is purely anecdotal. The "I'm smarter now that I'm an atheist" argument is laughable due to it's absurdity and irony. If one were truly 'smart', then they should be able to see the fallacy in using their own personal experience as proof. There were no IQ measurements before or after, just a vague feeling of superiority for breaking from what appears to be an abusive situation.
I get the need to validate your beliefs with arguments that make you feel superior. That's neither logic or proof, but rather an insidious bias that leads to full blown bigotry. I find it more than distressing that you succumb to these baser human desires at the expense of truth and kindness.
In fact, using cold data and your biased logic, we could say compared to Hong Kong, being an American makes you dumber. There's a 10 point difference right there. But is the difference causal or coincidental? Is ti due to genetics or environment? The question of IQ is not as simple as you or
@psychoslice would have us believe.
https://iq-research.info/en/page/average-iq-by-country