That’s a good question, @gio777. It’s also one that I have never thought of before.
I suppose the answer is yes. Confidence has a clear, positive effect on sports performance and you would expect that someone who had been taking performance enhancing drugs would have a greater belief that they would be successful than if they had not taken them – or they wouldn’t have taken them.
There are of course many negative psychological affects of drugs as well. The increased aggression may well have a negative effect on an athlete’s ability to relax, which is typically related to a good performance.