Lindsay Lohan will be jailed if she leaves the Betty Ford Centre early.

The 26-year-old actress - who began 90 days of court-ordered treatment nine days ago after pleading ''no contest'' to lying to police about being behind the wheel during a car crash last June - is reportedly ''freaking out'' and threatening to quit the rehab facility in Rancho Mirage, California because doctors have cut off her supply of Adderall but has been warned she will be hauled before Judge James Dabney and sent to jail if she quits.

A source told gossip website ''The judge overseeing Lindsay's case has made it crystal clear that if she defies the agreement, it's jail time.

''Judge Dabney signed off on Betty Ford and he expects her to remain there for 90 days. If she does, that will be a violation of her probation and the judge will send her to jail.''

Betty Ford's doctors rarely prescribe adults Adderall because they believe there are plenty of alternative treatments and also think that many people misuse the drug to control their weight.

Lindsay, who claims she suffers from attention deficit hyperactivity disorder (ADHD), has allegedly told friends that she cannot continue to stay there and wants to move to another rehab facility, which will allow her to continue taking the psycho-stimulant medication because she is terrified of putting on weight.

The insider said: ''Lindsay is absolutely freaking out about the prospect of gaining weight now that Adderall has been taken away.

''Lindsay has been able to eat whatever she has wanted and not gain weight for years and she attributes this to Adderall.''

Unlike other patients, Lindsay is not allowed to leave the facility at any point during her stay.

The troubled starlet was previously said to have freaked out and ditched her original plan to enter the Seafield Centre in New York for treatment because it doesn't allow its patients to smoke.