The unidentified medical “problem” that landed Mischa Barton in a Los Angeles hospital is that she “tried to kill herself”, a source tells a US website.

The actress was taken from her home by police on July 16 and reportedly placed on involuntary psychiatric hold at Cedars Sinai Medical Centre.

She was released earlier this week, and made her first public appearance on Tuesday.

The absence of a proper explanation for her hospitalisation has only served to fuel speculation about the cause, with most theories involving her alledged 'party' lifestyle.

But a source claims to E!Online that the truth is even darker.

"She tried to kill herself," a source close to Mischa says.

"She was being crazy that day [when she went to Cedars Sinai Medical Center]," says another insider.

Mischa's rep - who says his client is preparing to start work on her new TV show later this month - brands the claims "absolutely false."

Mischa at Paris Fashion Week in February