How can I get my parents to treat me like an adult when I am already 18?

The thing is that although you have done nothing to show that you are irresponsible, they might have when they were your age. Also, the world is full of people who ruin their life at that age. We all make mistakes and mistakes are good if you learn from them but some mistakes scar you for the rest of your life. Just feel special because you Parents care and try to show them your responsibility no matter how much they doubt. Be patient with them as they are just scared. Try to express to them that you know that they are scared and show them that they dont have to be. Any rebellion will hurt them emotionally but it may hurt you for the rest of your life so just be careful with your decisions. Some parents kick their children out at 18 and leave them to rot in their own trials by themselves. No matter how bad you think you have it, there will be someone who wishes they were in your place. Remember that! Good luck, its not easy but one day they will turn to you and say, I’m soo proud of you.

Get a job, support yourself, move out. You will then be an adult and they will have no choice but to treat you as an adult. In the mean while, good luck… If you are not earning money, it isn’t really your bank account. Seriously, there’s really not much you can do to make people treat you differently. Especially when they hold all the cards. If moving out is not an option right now, well suck it up. That’s part of being an adult, dealing with situations you dont like.