David is a happy, healthy and affectionate eleven-year-old boy. But he’s also autistic: unable to speak more than a few words; barely capable of expressing his most basic needs; oblivious to danger; blind to other people’s emotions.

There are 535,000 autistic people in Britain, about 1% of the population, and a further 2 million people either live with an autistic person or help to care for one. The condition is a thousand times more common than it was in the 1950s, yet it is still largely ignored and misunderstood.

A Real Boy: How Autism Shattered Our Lives – And Made A Family From The Pieces by Christopher Stevens with Nicola Stevens is David’s story, and that of his parents. They say that loving an autistic child is easy, but living with one is harder than could ever be imagined. We spoke to Christopher Stevens to find out why.

How did you discover your son was autistic?

David was an exceptionally difficult baby — he never slept for more than 40 minutes and screamed day and night. We didn't allow ourselves to think that anything could be wrong, until he was about 20 months and still couldn't learn to say a word. At first we thought he might have a hearing blockage — he'd suffered a lot of ear infections. Then we thought it might be a specific learning disability with language. He was assessed at the children's clinic here in Bristol when he was two years and three months, and that's when we were told he was profoundly autistic.

How did you feel? Did you know then what to expect?

We were devastated. There's no way at the beginning to put it in perspective, because it's too huge. All we could do was cope a day, or an hour, or usually a minute, at a time. Few people tried hard to explain what the future would hold — we asked about school prospects, life prospects, other health issues but the professionals always hedged their answers with 'possibly' and 'maybe'.

What surprised you most about autism?

The sheer prevalence of it. The professionals were telling us, in 1998, that only one child in 10,000 was autistic, but we met so many families in the same position as us. The family across the road, the family in the house behind ours, the family down the street... They are all involved with caring for autistic people. Everybody seems to know someone close to them who is affected by it. Yet in the mid Sixties, the National Autistic Society only knew of about 2,000 children in the whole country with the condition. Something must be causing this to spread.

What are some unexpected practicalities of caring for an autistic person?

David becomes very distressed if his mother leaves the house. He can't bear to think that she isn't there with him, or waiting for him. That puts an incredible strain on Nicky.

How much is David aware of what’s going on? What about your other son?

David's completely aware of everything... he just interprets the world differently. He can't understand a spoken explanation, and his autism prevents him from using imagination to see the probable outcomes of his actions. So he'll run into the road, and assume that all the cars will stop, because that's what has always happened in the past. He doesn't realise the traffic obeys rules, about traffic lights etc — he thinks it's all about him: the cars have to stop, because that's what he wants and expects. Our older son is, luckily, a very kind and empathetic child who accepts his brother's differences.

Have you ever had any negative experiences with people who don’t understand autism?

It's the positive ones that matter much more — the people who come across to make a friendly comment, and the ones who simply show tolerance. We find it intensely frustrating when professionals display their ignorance, especially when we're having to sit through meetings to discuss David's health and care. Some people, particularly in the health service, are highly paid but the nonsense they talk can be shocking. "Your son is like a garden full of weeds," one psychologist decided, at the end of six hour-long sessions. "You must uproot the weeds and replace them with flowers." A tabloid horoscope column wouldn't get away with spouting rubbish like that.

What do you think is the biggest misconception about autism?

Autism isn't about geekiness or ability with computers. The word is losing its impact, because it's being used in a derogatory way about people who, for instance, might not be gregarious. Society has made it unacceptable to use racist and sexist language — now we need to address the use of 'disablist' language.

That's an indication of how little importance is attached to disability rights — there isn't even a word to describe the bigots who use words like "autistic" as sneers. Mind you, people who use language like that in front of me usually find out that I can think of a few words to describe them.

What would people be surprised to know about autism?

David is very affectionate and loving. He loves to be cuddled and held. All people with autism are different, of course, but it certainly isn't a condition which automatically imposes loneliness.

How has writing the book impacted on your lives?

David's a celeb now. Of course, he always assumed that everyone did know everything about him. Now they can!

A Real Boy: How Autism Shattered Our Lives - and Made a Family from the Pieces by Christopher Stevens with Nicola Stevens; £6.99; out 28th February 2008. Visit www.amazon.co.uk