Joni Mitchell was in intensive care last night after being found unconscious in her home.

The legendary folk singer, 71, has struggled with poor health for years and has battled polio, scarlet fever and dengue fever.

In a recent interview, the River singer described the past eight years of her life as a 'survival blur.'

Her latest health scare came on Tuesday. Los Angeles fire officials said paramedics answered a 911 call in Bel Air, where Miss Mitchell lives, and rushed her to hospital.

She only regained consciousness in the back of the ambulance and is now said to be 'in good spirits.'

After the news of her illness broke, a spokesman for Miss Mitchell asked fans to: 'Light a candle and sing a song. Let's all send good wishes her way.' This struck a chord with her supporters and she became the top trending topic in the world on Twitter yesterday, with thousands of goodwill messages flooding the site.

Tributes were led by stars including Boy George and Billy Idol.

The Culture Club frontman wrote: 'A prayer for Joni Mitchell,' while the White Wedding singer posted: 'Sorry to hear today's news about Joni Mitchell. I sang on her Dancin' Clown single many moons ago, all the best for her recovery...'

Kirkcaldy-born crime writer Val McDermid added: 'Distraught to hear Joni Mitchell in intensive care. Her music inhabits my heart, my very soul.'

Canadian Miss Mitchell, an eight-time Grammy Award winner, has released 19 albums and was one of the biggest musical stars of the 1970s. Her album Blue has been ranked by Rolling Stone magazine as the 30th greatest album of all time. Pop star Taylor Swift, 25, is rumoured to be lined up to play her in a film of her life.

Miss Mitchell was forced to stop performing by Morgellons disease, a mysterious and controversial skin disease. She has described it as 'a weird incurable disease that seems as if it is from outer space,' but many doctors label it a psychological rather than physical problem.

Sufferers say the condition makes them feel painful crawling and stinging sensations under their skin, as if there were insects crawling beneath the surface.

Miss Mitchell said recently: 'I can't sing any more -- don't miss it. I can't play any more -- don't miss it. I've got all these instruments laying around and hopefully one day I'll pick them up.'

She has had a famously turbulent love life. As well as marriages to Chuck Mitchell and Larry Klein, she also had well-publicised flings with stars including Graham Nash, Jackson Brown, James Taylor and Warren Beatty.

A statement posted on the singer's website reads: 'Joni was found unconscious in her home this afternoon.

'She regained consciousness on the ambulance ride to an LA area hospital. She is currently in intensive care undergoing tests and is awake and in good spirits.'

s.creighton@dailymail.co.uk