Probably not the best delivery, but perhaps use of anabolic steroids in bodybuilding could have a counteracting detrimental effect to the brain (https://www.sciencedirect.com/science/article/pii/S000632231...).
I would guess this number is higher today
And in bodybuilding, unless someone is specifically a natty/natural bodybuilding competitor the answer is pretty much “all of them have been on gear at some point in time”. For other gym-goers, the answer is, nobody knows unless they tell you and since steroids are very illegal, people don’t tend to shout it from the rooftops.