How to stop all together. But you should also see a counselor or get professional help, because you can't just up and decide I'm not gonna drink anymore, it is hard. The professional help will guide you, and give you substitutes, and help you through your problems.
I believe u mean PEER pressure Yes it has an affect on the brain, it manipulates/pushes it to do something even if it doesn't want to. it can affect the body by harming urself from peer pressure.
if u DO mean pure pressure, as in pain, yes it has a physical affect and idk if it affects the brain.
I HOPE I HELP (ノ・ω・)ノ