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Britney Spears was carted off to the hospital for the second time in a month on Thursday — but an insider says her mental state has declined significantly since she lost custody of her sons Sean Preston, 2, and Jayden James, 1.

"It's really sad," the source told FOXNews.com. "Those boys mean a lot to her, and I can't think of anything worse than having your children taken from you. Ever since she lost custody she's been on a downward spiral — I think she feels like she'll never get them back and so everything else is meaningless."

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Photo Essay: Britney taken to hospital

A visitor from Miami who was staying near Spears' home described Thursday morning's mayhem — in which Spears was taken from her home to UCLA Medical Center by ambulance and escorted by a large police presence — as "dramatic."

"I am certainly glad I don't live in Los Angeles if this type of thing goes on regularly — what a joke," the guest told FOXNews.com. "If it weren't for all the big houses and sound-proofing, I doubt anyone nearby would get much sleep."

A high-profile neighbor said the Spears madness defeats the point of living in a gated community.

"One of the reasons I elected to live in a gated community is to avoid all these crazy celebrity goings on," the Summit Circle resident told FOXNews.com. "These paparazzi that set up camp here should be fined for trespassing — it is a ridiculous thing to have to drive through every time I want to get in and out."

That said, the scene early Thursday was more controlled than the one earlier this month when Spears also was taken away from her home in an ambulance.

On Jan. 3, police were called to her home when she refused to return her two young sons to ex-husband Kevin Federline, who has custody.

Officers had paramedics haul Spears to a hospital for undisclosed reasons. She was released after a day and a half in Cedars-Sinai Medical Center.

Spears has been in a highly public downward spiral since filing for divorce from Federline in November 2006.

Her bizarre antics include shaving her head bald, attacking a car with an umbrella and bringing along a paparazzo pal on trips to a courthouse in her child custody case.

Spears' child custody case has become a public spectacle, with her skipping depositions and twice this month arriving at the courthouse but not attending the hearing.

FOXNews.com's Hollie McKay and The Associated Press contributed to this report.