Singer/songwriter Joni Mitchell has opened up about the skin condition that forced her to scrap a rare performance at the 2010 Vancouver Olympics, insisting she was confined to her house and couldn't wear clothes.

The Both Sides Now singer suffers from the condition known as Morgellons, which some top medics believe is a mental illness linked to "false beliefs about infestations by parasites".

Mitchell tells New York Magazine her complaint is for real, adding that "fibres in a variety of colours protrude out of my skin like mushrooms after a rainstorm... They cannot be forensically identified as animal, vegetable or mineral."