‘We all know somebody with an eating disorder. They are pervasive in society. A lot of people have issues around food, even if they don’t come under the technical umbrella of what we define as an eating disorder.”

Eva O'Connor has just taken the final bow for her play Overshadowed, which has featured as part of the mental-health arts festival First Fortnight, at the Project Arts Centre in Dublin. She wants us to stuff our mouths with words about food, about control and about recovery.

O'Connor wrote the drama and appears in Overshadowed as Caol, the bodysuit-wearing embodiment of anorexia, who torments lead character Imogene with her jibes and taunts. Caol means "narrow" in Irish. There is no need to spell out the reasons behind the choice of name, says O'Connor.

Some say that the first thing you lose when you are anorexic is your sense of humour. “Anorexia sucks the joy out of your life. It’s very, very bleak. I think it has been sensationalised in the media, but I think it is dark in the same way that all mental illness is dark. It can eat up your entire life,” said O’Connor.

And she should know.

“I had anorexia from when I was about 14 and I recovered when I went off to university in Edinburgh,” the Clare woman says. “It definitely defined my teenage years.

“Suddenly life isn’t loads of things. You don’t derive joy from the things other people do, so socialising becomes difficult. Eating out becomes difficult. Concentrating becomes difficult. Reading becomes difficult. Your focus becomes so narrow. There is a really strict regime of what you are going to eat, how much you are going to exercise. You put yourself through all sorts of punishment.”

A helpful departure

Leaving Ireland for Scotland helped O’Connor to forget about anorexia. It remained part of her private inner life until she was leaving drama school in Sidcup, Kent, last year and entered a competition to write a play.

O'Connor told her friends that she was going to write about someone with an eating disorder, "and then I got the money and I was, 'Oh crap, I'm going to have to do this thing now.' " That play turned out to be Overshadowed, and she found herself talking to her friends about her past.

She has beaten anorexia, she says. “I got really amazing therapy that has basically allowed me to do what I do now. I sometimes think that if you don’t hit rock bottom, you are able to coast along in a mediocre way of thinking forever, so in some ways I’m grateful that I got sick and then I got better. I feel like I did my time in my teenage years. It was a really dark time and my family really helped me to get the help I needed.”

Making a drama out of her experience has been a positive experience for O’Connor. “I made this play because I always thought about anorexia like a demon on your shoulder,” she says. “My therapist used to talk about it like wearing a heavy cloak, and one day you will take that cloak off and just walk away from it. You will be free.

“It is not you. That is why I made Caol. She is completely separate from Imogene, the lead character. She is a little entity of negativity in herself and that is kind of how I see anorexia.”

O’Connor says that “there are many ways of seeing the demon, but the important thing is to see it as separate”.

Caol is a demon all right, wrapping herself around Imogene. Separate, but sometimes uncomfortably close. You can tell that O’Connor trained in dance for a year at Inchicore College of Further Education; her physicality is impressive. Imogene is trapped.

Heading towards oblivion

Overshadowed is bleak. Imogene skips her way towards oblivion, but hope is never extinguished. And although O'Connor knows that anorexia can kill, she thinks that, as with any mental illness, belief in recovery is key. "I really believe so much that you can recover, and I recovered," she says. "I don't believe it is something you will carry with you forever. Not at all."

She is concerned, however, by the fact that boys and men are being sucked into the eating-disorder abyss. “I don’t think you can underestimate how hard it is for guys too. Whether or not they develop an eating disorder.”

O’Connor is also concerned that a trend for “clean” eating might be being used to distract.

“People with eating disorders can hide it for a long time by being ‘I’m gluten-free’, ‘I’m dairy-free’, ‘I’m everything-free’. The craze around super-healthy eating can definitely lead to eating disorders,” she says.

According to O’Connor, like with any mental illness there’s no road map for anorexia. The main duty of friends is to be a friend, she says.

“It is to accept and love and always include. To invite someone, even if they stop turning up. Be there for them unconditionally. Encourage the person to get professional help. Professional help and help from friends and family should be completely separate things.”

The media shouldn’t take all the blame either, she says. “It is up to us to find a way to live out our lives as we want. We need a whole paradigm shift, instead of saying it was ‘really bad how that bikini body was pushed’.”

She advises taking control. “You only have one life and if you are going to put all your effort into being a certain weight, your horizons are just going to shrink.”

Personal journey

This is not O'Connor's first time making a drama out of her personal journey. Last year her play My Name Is Saoirse, for Sunday's Child, the theatre company she runs with fellow Irish woman Hildegard Ryan, won a First Fortnight award. The play is about a girl from Limerick who gets pregnant and has to go to England for an abortion.

O’Connor makes no bones about the fact that she had an abortion in Scotland. “Ironically, the majority of the medical staff were Irish, so that was what made me want to write the play,” she says. “I wanted to write a compassionate story which focused on a personal journey and made people focus on the realities of a teenager getting pregnant.”

She thinks women in Ireland should have access to safe, legal abortion. She says that it "is the number-one thing on the Irish agenda right now. We are lagging right behind and there's a massive appetite for change. Everyone's bored waiting at this stage. We are so bored. If men like Enda Kenny could just cop on and talk to their wives and daughters and sisters, then surely they would realise we don't live in a bubble."

She says she is ashamed of Ireland’s laws, “but I’m not ashamed that I had an abortion. I think shame is like old news now. We need to close the door on the days of Catholic shame. It’s a new era. It is very, very bad publicity for Ireland.”

O’Connor intends to move away from drawing on personal stories, she says. She is writing a new play and will tour her current offerings. Meanwhile she is throwing supportive metaphorical arms around the Waking the Feminists movement from her home in London.

“There is a long way to go for equality in our industry, but there’s a real appetite for change and I feel like I’m really lucky to be coming up in this generation,” she says. “You don’t sit at home thinking, ‘I’m a female playwright; life is so hard for me.’ You just forge your way and hope it will happen. But it is amazing to be part of a generation where there are so many hungry, supportive women who want to change things, and I think we will.”

She would love to get one of her plays on to the Abbey stage. "They need more women, so count me in there."

Meanwhile she is using the lessons she has learned from writing about anorexia. “As soon as you channel all that energy into something else, your possibilities are so much greater than when you are just eating a few apples a day.”

OVERSHADOWED: AN EXTRACT

Caol: So now she's referencing nursery rhymes / making light of her disgusting crimes.

Imogene: Or or . . . having been stupid enough, weak enough, to let it cross my lips, I should have legged it to the bathroom, rammed my fingers down my throat and retched, until I regurgitated every last morsel, along with the entire acidic contents of my empty stomach. That's what I should have done. I know. Sure, isn't hindsight a great thing?

Caol: How dare you address me with that sarcastic tone / you'll pay for this now we're alone.

(Caol begins to forcefully undress Imogene, ripping the buttons on her school shirt and poking at her flesh.)

Imogene (pleading): It's Friday! It's the weekend. It's when people let their hair down. They straighten it, they curl it, they go to parties, they get drunk, they shift each other. They have fun. And on Monday they come in with stories and secrets and scandals. That used to be me. I used to have a life, I used to live for the weekend like everything else. But I don't get that Friday feeling any more. Friday means nothing to me now. It doesn't mean freedom, or fun – it means more time to exercise, it means 48 hours of no school while we hole up in here, and control and calculate, monitor and minimise, and hit targets. Or, in my case, fail to. And today I just snapped.

Caol: Snapped? Are you some kind of elastic band / you did not snap, you exploded, expanded / outwards by miles I can see it clear / in your arms, your face, your thighs, your ears / in your all-over body, in your biscuit flesh / you're a failed anna girl, you're a pitiful mess / You're a pile of crumbly lippidy mush / there's nothing more to be discussed.

• Overshadowed by Eva O'Connor is published by Bloomsbury