Matt Haig's first non-fiction work, Reasons to Stay Alive, is an authentically optimistic account of his experiences with depression and anxiety, offering insight and advice on the illness that will effect one in five of us at some point in our lives. He spoke to Rowena McIntosh about his story, and writing the book …

The end of your novel The Humans was the first time you ‘came out’, to use your phrase, about your depression. How did how decide to write a book about it?

I've known I'd really talk openly and as honestly as I could about depression ever since I came out of the worst bit of it about ten years ago but I had no idea what form that would take or how I would do it. I don't think I would have written this particular book on depression if I hadn't blogged about it. The response I had was really amazing. I think that anyone who talks totally honestly about their experience of depression gets a generally positive response and this fear we have about coming out is often unfounded because it’s such a common thing. One in five people will have a major depressive episode in their life so it’s really time for the stigma to totally be erased and that’s hopefully what my book will contribute to.

Reasons To Stay Alive is about your personal experience but it isn’t a straight memoir. How would you describe the book?

I never thought I'd write a book that resembles a memoir because I always thought to write a memoir you'd have to betray people. I was looking for the way to tell the story and found one which isn’t really a factual overview of depression; it's not really a self-help book, it's not really a memoir, it just contains bits of all those things.

In the book, you try to explain what depression is. What do you think are the most common misconceptions?

There are still lots of educated and intelligent people still doubting depression as an illness. I think compared to any other physical illness, depression comes with a judgement. It’s seen as a personality failing. When you have experienced it, there is absolutely no question; you know you are broken in some way. The main misconception is you can pull yourself out of it. You can't snap out of it any more than you can out of asthma or arthritis.

You’ve done a lot of research into depression. Were there any facts you learned along the way that particularly shocked you?

For me what was incredibly shocking was the way suicide rates vary from country to country. One in five people in Greenland attempt suicide in their life, and no one knows why. Depression is universal. People might call it different things but it's not as Western as people used to believe. We're more open and able to call it depression but it’s there in every community. Although depression is this universal thing, suicide rates change, so there is no reason why it has to often end in that tragic way.

You personally didn’t take medication for depression. What role can it play in helping?

I was on anti-anxiety medication diazepam but I wasn't ever on something officially for depression, and the reason for that is I was scared. One of my symptoms was to be very phobic about things that changed my state of mind. I didn't drink for a decade, I shunned everything, even Nurofen. I know people that medication has worked for and it could have worked for me. My main advice is you are your own laboratory. Depression is complicated, more than one thing causes it and it’s usually more than one thing that cures it. It is about trial and error and trying to be alert to yourself and what makes you feel better.

Your family feature in the book: you move back in with your parents and are cared for by your girlfriend (now wife) Angela. Did you ask them what they remember of their experiences of being with you at the time?

I didn't. Angela was closely involved when I was writing it and I kind of know how she felt because we've talked about it so often. It’s more nerve racking with my parents. Me talking candidly about depression might make them sad or uncomfortable and I didn't want to do that so I was nervous when my mum read it, but both of them have been very supportive. I wanted to portray myself rather than other people. I wanted to focus on the depression even though, talking about that time, those people are inevitably brought in.

What would be your advice for being there for someone with depression?

Listen, understand, and don't judge. The problem with depression is it is invisible. It’s hard because outwardly you look so normal and if you’re sitting on the sofa for days, scared to go outside it can be incredibly hard to understand. It is the hardest thing in the world I think to be there for someone with depression.

When you were writing the book you asked people to tweet their #reasonstostayalive. How was the response?

It was about halfway through writing it and that was the first time that I thought this is going to be well received. We're at a point now where there’s still a lot to learn but our confidence is up about talking about this without the stigma. The internet has played a part in that. Social media, for all its many faults, gives a voice to more people and it’s easier sometimes to type something than it is to go out into the world and speak about it.

The book has been endorsed by lots of famous people including Joanna Lumley and Stephen Fry, and you’ve included a list of famous people who had/have depression. What role do you think people in the public eye can play in the discussion about mental health?

It’s already happening. People like Stephen Fry and Ruby Wax have been very public about talking about it. It's so important to talk because when you are depressed you feel so alone and to know other people have felt similar things is therapy in itself. There is serious charity work to be done, serious research to be done but I think the single most important thing is talking about it.

Reasons To Stay Alive is out Thu 5 Mar, published by Canongate.

Matt Haig launching his book at Head on Fire: Closing the Divide Between Physical and Mental Health, St George’s Tron Church, Glasgow, Tuesday 10 March.