Amanda Bynes was allegedly taking powerful medication to control her weight before her public meltdown.

The 27-year-old actress, who was placed under an involuntary psychiatric hold in hospital in Los Angeles on Monday (22.07.13) after lighting a fire outside an elderly woman's home, was reportedly using Adderall to suppress her appetite, which may have affected her mental health.

A source told gossip website RadarOnline.com that since she was admitted to hospital after being arrested for starting the small fire in a stranger's driveway, the 'Easy A' star, who previously admitted she had an eating disorder, ''has been demanding that doctors give her Adderall, which they are refusing to do. Amanda has been on Adderall for years for Attention Deficit Disorder. Like many other young women in Hollywood, Amanda took the drug to stay thin.

''The problem with someone like Amanda dealing with serious mental health issues, is that Adderall can make their condition worse. For Amanda, this has meant increased paranoia.''

It was previously reported that Amanda's medical team is seeking an extension on the 5150 order to keep her in hospital for more than 72-hours, so they can properly diagnose her.

Doctors treating the star, who has reportedly been displaying signs of schizophrenia at a psychiatric facility in Ventura County, California, ''have formally petitioned to keep her for further treatment and assessment for the next fourteen days.''

An insider said: ''Amanda will likely attend the proceedings, which will be closed to the public.''

The actress's parents Lynn and Rick plan to appear in court on Friday (26.07.13) to try to secure a conservatorship, that would see them gain legal control of Amanda's welfare and finances until she gets her life back on track.