It does the same thing it does to the others afflicted by it: it makes you strong, dumb, and slow, with the effects growing the longer you have it. This is represented in the game by causing physical base stats (str, end) to go up, and mental & agility stats to drop.

... but, crucially, when you cure it, the bonuses remain, while the penalties go away. So you can use it to pretty much max out your strength and endurance.