Jamie Lynn Spears, Britney Spears Was 'Erratic, Paranoid, Spiraling' During Interview

Jamie Lynn Spears says she's in no position to evaluate Britney Spears' mental state, but that's exactly what she did in her book, clearly suggesting her big sister had mental issues.

In an interview that aired Wednesday night on "Nightline," Jamie acknowledged she wrote in her memoir that over the years Britney's conduct was "erratic," "paranoid" and "spiraling."

She described an incident in the book where she says Britney took a knife, and locked herself and Jamie Lynn in a room, saying she was scared. As for why she included the story ... Jamie Lynn essentially said the book was a memoir and she was recounting stories that had an impact on her life ... namely, she says she suffers panic attacks from past trauma.

Up to now, it seemed Jamie Lynn was trying to extend an olive branch to Britney, but based on what we now know she's saying in the book, she's clearly trying to make a case that Britney has serious mental issues.

She also says her relationship with Britney fell apart during the pandemic, recounting a story where she says Britney was holding her toddler, Ivey and got in Jamie Lynn's face, cursing at her. Jamie Lynn says her 12-year-old daughter tried to mediate the situation. As for their parents' reaction ... Jamie Lynn says it was simple ... Don't Upset Britney -- and that angered Jamie Lynn.