MANY health practitioners suggest that the figure is much higher and most published research has found that the lifetime occurrence is closer to 50pc. So what exactly does it mean to be normal?What about that recurring back injury or the vomiting bug you had last year? Do they disqualify you from being normal? It is 'normal' to suffer from a physical illness now and again and for most people to expect to recover or at least to maintain their condition well enough to lead a normal life? We tend not to stigmatise people for seeking treatment for a broken leg or a sinus infection and yet, if their illness is mental rather than physical, they are seen to be fair game.
A study carried out last year by St Patrick's University Hospital in Dublin found that 20pc of people believe those suffering from mental health problems are of below average intelligence and 42pc consider seeking help for a mental health problem to be a sign of weakness.
A frightening two-thirds of respondents said they would discriminate against hiring someone with a history of mental illness and almost a third said that they would not willingly accept someone with a mental health problem as a close friend.
If that was not bad enough, a 2010 Amnesty International study undertaken at DCU found that 96pc of people with a mental health problem said they had been treated unfairly because of their illness.
The sociologist Erving Goffman defined stigma as, "the process by which the actions of others spoil normal identity". So it seems that if you have ever had a mental illness in Ireland, you can expect to have your normal identity spoiled when you are applying for a job, a mortgage, health insurance, or even just talking to a friend.
Even the casual language used to describe mental illness is overwhelmingly negative. People are described as "crazy", "mental"or "psycho". The media loves to analyse the mental health of criminals, while soap operas and films often portray the mentally ill as murderers and child abductors.
As a result, in Ireland, mental illness is seen as more of a social problem than a health problem. It scares us because we don't really understand what it is. If we feel we might have it, it scares us even more and we can suffer for years before seeking help.
In the film What Stigma? by James Keating, Boards.ie director Tom Murphy talks about his own experience of depression. "It takes a great deal of courage for somebody to stand up and say, 'I'm not well, I'm not feeling great', and you shouldn't feel like you're doing something hugely momentous, you should be able to talk about it freely." Murphy points out that, when people try to improve their physical strength, nobody thinks of them as physically weak.
Similarly, when he hears how someone is overcoming depression, he thinks of them as mentally strong.
In 2011, 525 people took their own lives in Ireland. This was up from 486 in 2010. It is estimated that, for every person who takes his or her own life, 20 may attempt to kill themselves.
And yet, €35m that was to be invested in modernising mental health services during 2012 was used instead to subsidise cost overruns in other parts of the health service. At the same time, policymakers prefer to blame social media for several recent high-profile suicides.
Paul Gilligan, CEO of St Patrick's University Hospital, says that we need to acknowledge our own experiences and fears about mental health, confront our biases and educate ourselves on the true nature of mental health and well-being.
He says that we need to start this education in the classroom by making mental health awareness a core part of the school curriculum. Gilligan also feels the negative perception of mental health issues among doctors, policymakers and health managers needs to be tackled in order to improve services and encourage people to seek help.
See Change (www.seechange.ie) is an alliance of organisations working to change public attitudes towards those with mental health problems. The First Fortnight arts festival (www.firstfortnight.ie), on until Saturday, aims to challenge mental health prejudices by creating a different space in which people can discuss issues. All involved agree that we need to bring the issue out of the closet.
"If you think you don't know someone who has been affected, it's just that you haven't had that conversation," says Jane Arigho, of Headline. "These subjects affect absolutely everybody in this country."