Mischa Barton has reportedly lost all her friends following her wild behaviour.

The former 'O.C' actress — who was sectioned last week at Los Angeles' Cedars-Sinai Medical Center after being placed under a 5150 hold, a piece of US legislation which means she poses a danger to herself or others — is no longer in contact with many of her pals, including Nicole Richie, as they don't approve of the way she is living her life.

A source said: "In the last few years, her dark side has really come out. Her friends, like Nicole, want to be supportive but they really can't be around her too much. She's too volatile. It makes us sad, but we're also like, 'Pull it together and get help already.' "

Nicole — who is currently pregnant with her second child — and Mischa reportedly fell out in 2007 after they went to a mutual friend's barbeque and Mischa was taken to hospital after falling ill.

The source added to People magazine: "Nicole is focused on motherhood and her family. She considers Mischa a dear friend but she's also a mother who can't be around too much negative, unsafe behaviour. Mischa is one of the reasons that Nicole is mostly with her other mom friends these days, not the party girls."

It wasn't just Nicole who distanced herself from Mischa after that incident. Another insider said: "Most of her Hollywood friends have distanced themselves from her since that party. After that happened, her friends thought it would be a wake-up call, but it wasn't."

It has been alleged the actress has been using drugs and alcohol to cope with her money problems and stuttering love life.