Joni Mitchell has opened up about why she doesn't want Taylor Swift to portray her in a biopic.

Swift was mentioned as early as 2012 in connection with a big-screen adaptation of 'Girls Like Us,' a book that focuses on the impact of autobiographical female singer-songwriters like Mitchell, Carly Simon and Carole King. But Mitchell revealed last fall that she'd "squelched that," complaining that all Swift represented was "a girl with high cheekbones."

The 71-year-old singer-songwriter now admits that she's "never heard Taylor's music" in an interview with New York magazine. "I've seen her," said Mitchell. "Physically, she looks similarly small-hipped and high cheekbones. I can see why they cast her. I don't know what her music sounds like, but I do know this -- that if she's going to sing and play me, good luck."

Mitchell also discussed her battle with a rare and controversial skin condition called Morgellons that kept her from performing her early hit 'Both Sides Now' at the 2010 Olympics in Vancouver. Mitchell revealed back then that she'd been confined to her home, unable to even wear clothing because of the ailment, which many doctors claim is psychological.

Mitchell said the illness is incurable, adding that "fibers in a variety of colors protrude out of my skin like mushrooms after a rainstorm ... They cannot be forensically identified as animal, vegetable or mineral."

News reports have criticized the condition as delusional, and the Mayo Clinic is likewise circumspect. Describing it as "an unexplained skin disorder characterized by crawling sensations on and under the skin," the Mayo report notes that "symptoms of Morgellons disease are very similar to those of a mental illness ... involving false beliefs about infestations by parasites."

Mitchell has given up singing but released a personally curated four-disc box set of her work last year titled 'Love Has Many Faces: A Quartet, a Ballet, Waiting to Be Danced.'

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