Alcohol can and does cause permanent damage. I just have not seen anything that says alcohol makes concussion damage permanent. I was told by my neuro at 16 years old to stay away from alcohol because its effect would be much worse with a concussion injury. Alcohol is a neurotoxin. It will likely delay your recovery.

I've heard it stated that getting blotto drunk has a similar effect on your brain as getting a concussion.

But, what ever you did, you cannot change it. You can only effect your future behavior. Learn from your mistakes and move forward with your life. Anxiety will only make you symptoms worse.