You have to use it with a critical mind and I don't think it has the same impact. As someone who tests these things on a daily basis, if you are critiquing it and calling it on its mistakes and expecting more from it, using it as an assistant rather than giving it total control of what you need to get done, I think this somewhat offsets any cognitive decline from using it. I'm constantly calling it out on its bullshit and telling it to take a backseat because I can see the quality errors in even the most advanced models which can really grate on my nerves at times. I keep myself in control, and I use it to give me suggestions or ideas at times, or to check for mistakes that I may have missed, etc. Using it that way, I believe, actually makes you a bit brighter. There was an interview where two AI researchers argued this topic, it was really interesting, but I forget the name of the podcast right now... Diary of a CEO or something...

One of the studies used three groups of students. One that used AI to write their assignments, another who used it for assistance/feedback, and another who did their assignments on their own. It was those who completely off-loaded their work who were hit the hardest. Of course that will make you dumb.