Imagine being in a difficult, damaging, draining relationship. Despite your years of commitment, it is going nowhere and the strain is making you ill. When this happened to Danu Morrigan she took what seemed the healthiest option: she got "divorced". The thing is that the relationship in question was with her mother. She doubts she will ever see the woman who gave birth to her again. And as her father sided with her mother, she doesn't expect to see him either.

There is no legal mechanism that allows people to "divorce" their parents but, says Danu, 48, that is what it feels like. "To all intents and purposes, it's divorce," she says. "It may not have a basis in law, but it's just the same."

For most people, cutting off contact from their parents would be going too far, however impossible their family problems. "I explain to people how difficult it all was. I think they are listening, but then when I get to the part where I say, 'so I don't see her any more', they suddenly shriek: 'What! You don't see your own mother?' And I think, weren't you listening? It was a nightmare. There was nothing else I could do …"

So what did Danu's mother do that was so terrible? She classifies it as emotional abuse. "She's a narcissist. She is convinced she's perfect – and since she's perfect she can't do anything wrong. It's subtle, but everything in our family life was all about her – I simply didn't exist, except as a reflection of her or to bolster her overinflated idea of herself."

Danu is one of four adult children and two of her siblings have also cut off parental contact. "There was no alcohol abuse, no physical violence and from the outside, you might have thought our family was idyllic. But everything was about her – never about me or my siblings," she says.

"On my 10th birthday, she decided I needed a handbag, bought it for me and was devastated when I wouldn't use it. But I was a tomboy – a handbag was the last thing I wanted. She had no sense of who I was or what I wanted. That was typical."

When Danu didn't want the gifts or lifestyle her mother tried to foist on her, the message she got was that she wasn't good enough. "Because I wasn't the person she wanted me to be, I was unacceptable: she used to say: 'Nothing's right for you, you're always complaining.'"

When Danu married and had a child, her mother's jealousy was tangible, she recalls. "She resented every bit of attention I got – when I miscarried, she turned it round to be about her. Then when I had my son she was completely uninterested in him."

Meanwhile, says Danu, her father, was an "enabler" who allowed, and sanctioned, his wife's self-centred approach to life. "On my wedding day, my father said in his speech that he wanted to toast the most beautiful woman in the room … my mother," recalls Danu. "The irony is that she wasn't even in the room – unable to bear an event that wouldn't focus on her, she'd absented herself and was in another part of the building."

Things might have carried on had it not been for a family meal to which Danu brought a friend. "I always kept friends away from my mother because she was so embarrassing, but on this day there was no way out of it. The funny thing was, my mother wasn't especially bad – just her normal self. She didn't ask anyone how they were, or what they were doing, but went on and on about herself, barely spoke to my son." Danu's friend was appalled. "She said, 'Do you realise how truly dreadful she is?'

It was an epiphany: I thought, it's not just me – it really is my mother. She exhausted me, drained me. I got nothing from her because she gave nothing. I was depressed, ill, ground down. I had to get out."

She waited till her parents next telephoned and told them there would be no more family meals, no more phone calls or Christmas get-togethers – no further communication, in fact. That was four years ago.

Dr Pat Frankish, a consultant clinical psychologist, says she has nothing but admiration for people like Danu. "Someone in her situation has had her identity, her vitality and her energy sapped – and if she stays in touch with the person who is taking all that from her, she'll be unable to maintain a sense of herself. It's a question of whether you succumb or survive – and she has chosen survival."

Danu now runs a website for other women who also feel that they are victims of what she claims is adult child abuse. She says between 50 and 100 people post messages on a regular basis. "I don't encourage others to do as I've done and go for no contact with their parents. But if you've got a narcissistic mother, there's no way you'll ever have a real relationship with her."

Pat Frankish's advice, for people who experience extreme difficulties in an adult parent-child relationship, is to seek psychological help from a trained therapist. "You need to work out whether the problem is yours or your parent's, and then decide what to do about it," she says.

The question Danu is most often asked when she reveals she has severed contact with her parents is about what will happen when they die. Will she go to their funerals? Will she mourn? "I can't know how I'll feel, but I don't expect I'd want to go to their funerals," she says. "I couldn't go and accept condolences, but nor could I go and risk people telling me they never liked my parents."

There won't be a dilemma over any money her parents might leave her – she is sure they have written her out of their wills. "In our family, there isn't a lot of money anyway. But for some of the people who post on the website it's a big issue. Some feel they've been through so much, put up with so much, that money would be some recompense. Then again, you hear of people who put up with terrible situations for years – then the mother leaves it all to the cat home."

Since the break, she has felt "transformed … I can't overstate the difference it has made. My depression has lifted, I've lost weight, I carry myself more confidently and I've made changes that have put my life on a much better track. I'm so much happier – I'm not always dreading the next phone call or visit. Most importantly, I know I'm not that fatally flawed, bad person my parents used to make me think I was.

"They made out that I was the person with the problem; but that wasn't true. They are the people with the problems – I'm actually fine. And without them, I'm a whole lot happier."

You're Not Crazy – It's Your Mother by Danu Morrigan is published by Darton Longman and Todd, price £9.99. To order a copy for £7.99 with free UK p&p, go to theguardian.com/bookshop or call 0330 333 6846. Danu Morrigan is a pseudonym. More information:

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