As the singer-songwriter languishes in hospital, confusion grows. Is she in a coma, as court papers suggest, or are supporters right to say she is alert and well?

EVER since she was found unconscious in her Los Angeles home at the end of March, Joni Mitchell's publicity machine has sought to reassure her fans. The musical icon who wrote one of the most poignant lyrics of the 1970s - "They paved paradise / And put up a parking lot" - was said to be "resting comfortably" in hospital.

Fans were told she was simply under observation and enjoying the flood of Twitter and Facebook messages flowing through a specially created website, We Love You, Joni!. More than 13,000 people have contributed to it, a testament to Mitchell's enduring appeal.

Leslie Morris, one of her oldest friends, posted that "contrary to rumours . . . Joni is not in a coma. Joni is still in hospital - but she comprehends, she's alert and she has her full senses. A full recovery is expected." Quite a different story, however, was heard last week by a Los Angeles court as Morris was given control of the 71-year-old singer-songwriter's affairs.

Morris's legal petition claimed that Mitchell "remains unconscious and unable to make any responses, and is therefore unable to provide for any of her personal needs". Paul Vespa, a professor of neurology and neurosurgery who is in charge of Mitchell's case, provided evidence that her mental faculties - including being able to communicate, to recognise objects and people and to have any sense of her surroundings - are so impaired that she is unable to consent to medical treatment.

Morris was granted the role of "conservator", which gives control of a person's day-to-day life - but not their finances - if they have no relative to care for them. Morris reiterated her hope of a full recovery. Seeking to allay the fears of fans, a statement said the role simply gave her "the authority - in the absence of 24-hour doctor care - to take decisions for Joni once she leaves the hospital. As we all know, Joni is a strong-willed woman and is nowhere near giving up the fight."

Strong-willed is barely the half of it. Mitchell has been doing things her own way since her musical talent emerged when she was a child in western Canada. Her distinctive guitar tuning came about because she contracted polio at eight years old and the disease affected her fingers. When she taught herself to play using a Pete Seeger songbook, she devised alternative tunings that became "a tool to break free of standard approaches to harmony and structure".

Her distinctive singing voice developed without vocal training. "I used to be a breathy little soprano. Then one day I found that I could sing low," she once said. "At first I thought I had lost my voice for ever. I could sing either a breathy high part or a raspy low part. Then the two came together by themselves. It was uncomfortable for a while but I worked on it, and now I've got this voice."

Mitchell, the daughter of a Canadian air force instructor turned grocer, started smoking when she was nine and would "get on my bike, looking for a beautiful place, a grove of trees or a field, and go among the bushes and smoke, and that always gave me a sense of wellbeing".

Artistically gifted but temperamentally unsuited to formal schooling, she never read a book unless she had to but was able to let her imagination run free. She dropped out of school, but then went back into education and on to study art. By that time she was already playing at local clubs, though "music was firstly a hobby to make money to smoke at art school".

The claim made in the LA court last week that she has no relatives is incorrect. In 1964, trying to make a living as a folk singer in Toronto, Mitchell learnt she was pregnant by a former boyfriend. She was living in an attic room with no money and was terrified of her family finding out: she gave her baby girl up for adoption.

In 1997 they met again after her daughter, Kilauren Gibb, tracked her down. Mitchell was overjoyed to find she was a grandmother but the reunion did not last. She complained of Gibb's behaviour and in 2000 the police were called to Mitchell's house when Gibb claimed her mother had slapped her during an argument.

According to Mitchell, the experience of giving up her baby had been her initial inspiration as a songwriter. Unable to talk to the person she wanted to talk to, her daughter, she had become "attuned to the whole world". It had also prompted the chain of events that took her to the United States after she met an American singer in Toronto and was briefly married to him.

By 1967 she was immersed in hippie culture in Los Angeles and signed up to a record label. Her self-titled first album - also known as Song to a Seagull - was released the following year. The second, Clouds, was recorded while she was living with the singer Graham Nash in the Laurel Canyon area of LA (having left David Crosby, another member of the supergroup Crosby, Stills, Nash and Young). She would later have affairs with her fellow singer-songwriters James Taylor and Jackson Browne and the actors Sam Shepard and Warren Beatty.

From the start Mitchell was wary of record company executives. She produced her own songs and designed her record sleeves. She won her first Grammy in 1970 and sold millions of records. But shortly afterwards, aged 27, she felt burnt out and left the music business for two years. "I lost my daughter. I made a bad marriage. I made a couple of bad relationships after that. And then I got this illness - crying all the time. That was the year I burst into tears. They walked on the moon, I cried. Something was biochemically off then. I couldn't be around people because everything made me weep."

She diversified into jazz and other genres, and built up her formidable reputation. Songs such as Chelsea Morning and Big Yellow Taxi led Rolling Stone magazine to call her "one of the greatest songwriters ever". She was inducted into the Rock and Roll Hall of Fame in 1997 and received a Grammy Lifetime Achievement award in 2002 with a citation describing her as "one of the most important female recording artists of the rock era".

Bouts of depression may have prompted her wish for solitude in recent years. She has lived as a virtual recluse, creating her artworks (she once said she was "a painter derailed by circumstance") and occasionally surfacing to make critical comments about other artists - notably Bob Dylan and Taylor Swift - and to berate the music industry.

In 2010 she revealed she was suffering from Morgellons, a rare disorder usually diagnosed by medical professionals as delusional parasitosis. Those afflicted believe, among other things, that they can feel insects crawling over their skin and into their eyes. It is sometimes thought to be linked to previous drug use. Sufferers can also report fibres protruding from their skin. Mitchell once described it as a "weird, incurable disease that seems like it's from outer space" and said she sometimes felt as if she were being "eaten alive" and could not bear to wear clothes. The condition has stopped her performing and travelling.

What produced her current illness isn't known. Whatever ails her, the likelihood is she will not sing again. As recently as six months ago, when she was interviewed for The Sunday Times by Bryan Appleyard, she told him: "Music is over for me, pretty much . . . You have to know when to give up." Appleyard visited Mitchell at her terracotta-coloured mansion in Bel Air, gaining a rare insight into her private world. Although she was sharp and lively-minded, it was, he said, "strange, like something out of Sunset Boulevard, this woman living alone in this huge house".

"It's a sad end to a career that's never obeyed any of the rules of the pop industry," said Dan Cairns, chief pop critic of The Sunday Times. "I bet if you stopped music fans in the street, at least half of them wouldn't know Mitchell is Canadian - she's so associated with California. Yet even there in the 1970s she was seen as a kind of mystical outsider with her diarising, candid yet icy songs. She has a sense of otherness that has gradually hardened around her like a shell.

"She's a vocal feminist who has made many serious and important points about the music industry. My fear about this hospitalisation is that it will play into the new narrative of the lonely woman whose life revolves around her cigarettes and her paintings - and probably her cats. It feels disrespectful to someone whose influence has been so huge and whose significance as a musician is up there with the greatest."