Amanda Bynes -- Parents File for Conservatorship

Amanda Bynes’ parents have just filed court documents asking a California judge to impose a conservatorship on their daughter due to her apparent mental illness, TMZ has learned.

The conservatorship would empower Amanda's parents to have decision-making authority over certain aspects of Amanda's life ... though it's unclear, at this point, what specific aspects Amanda's parents are looking to control.

Amanda is currently being held by authorities on a 5150 psychiatric hold ... which was put into place earlier this week after she lit a fire on the driveway of a random elderly woman in Thousand Oaks, Ca.

TMZ broke the story ... doctors at the psychiatric hospital say Amanda is showing signs of schizophrenia.

TMZ has learned the documents outline Amanda's bizarre behavior and highlight the troubling string of incidents -- including the driveway fire -- leading up to the 5150.

There will be a court hearing Friday.

It's worth noting ... it's VERY difficult to get a conservatorship in California.

Story developing ...