How Does the Age of Majority Affect Runaways

My question involves juvenile law in the State of: Mississippi
I am 19 years old and planning to move out of state next fall when I am 20. I am planning to whether my parents agree or not. Only today have I found out that Mississippi's age of majority is 21. Will this affect me if I leave without their permission? Will the police pursue a runaway who is over 18? Thanks for the help.

Relax, it's 18 other than a few things relating to inheritance and trusts (and of course drinking).