PS at 800mg (active PS only - NO PS COMPLEX) can reduce cortisol levels by appx 30% when they are abnormally high. If they aren't abnormally high it does nothing. In most cases cortisol blocking is overrated unless you are under a lot of stress and/or get too little sleep.
IF you match the above criteria than 800mg of active PS will do the trick - pricey though. Supposedly Keto-7 DHEA does this as well at a lower cost but I've seen no studies to back claims. And of course blocking the effects of cortisol vs reducing cortisol itself works - Supposedly Methoxy/4AD does this and with little doubt a good cycle of AAS shuts down the effects of cortisol (if there are any to worry about).
I took prosource's brand of Phosphatidylserine a year ago, and i think it worked pretty well...coulda been all mental. i'd buy more to try now i'm a poor college student