Stan Mould always knew he had problems, he just couldn't figure out why. He was extremely disorganised, unable to prioritise or plan ahead. As a senior business analyst at a building society, he found it impossible to concentrate for more than 10 minutes at a time. His speech was loud, fast and often slurred.

He was also intolerant and impatient - unable to keep his thoughts in check. Managers were not happy with his progress or his attitude. During one business meeting he shouted at the company solicitor. 'I called him a dickhead,' recalls Stan. 'It went down like a lead balloon.' His bosses perceived him as a lazy employee with a vicious temper.

Stan, whose marriage ended in 1990, admits he regularly used to 'rub people up the wrong way' with his outspoken views. 'I used to be furiously angry,' he concedes, 'and always shouting.'

Sounds like most of us on a bad day. But Stan, 45, felt that his symptoms added up to something more. And in 1992, while looking through a book about allergies, he came across a condition diagnosed in the United States and called Attention Deficit Disorder (ADD). Although the syndrome is similar to an adult version of childhood hyperactivity, he discovered, only two-thirds of sufferers are actually overactive. What seem to be universal traits in sufferers, though, are extreme distractibility and impulsivity, in behaviour as well as speech. Stan says: 'I read the explanation and thought, 'Crikey, it's me.' '

So Stan left his job, went to the US and was officially diagnosed as an ADD sufferer. 'As soon as I realised I had it, my whole stance changed,' he says. 'It made me realise I wasn't an idiot.' On the contrary, Stan was informed that he had an IQ of 154, and he is now a member of Mensa.

He became calmer and more tactful. Four months ago he moved in with Linda Brewer, 42, and her 13-year-old son Simon, who is an ADD sufferer. Stan and Linda met through Ladder (the National Learning Attention Deficit Disorder Association), a self- help group that Stan set up about 18 months ago while living in Wolverhampton and which he now manages from Linda's home in Morden, south-west London.

The house does not seem designed with the average ADD sufferer in mind: a ringing telephone and the sound of children playing downstairs in Linda's private nursery conspire to distract Stan from conversation. He begins to explain the difference between male and female ADD symptoms, but his attention is immediately disrupted by a car alarm outside.

A characteristic of Stan's conversation is continual digression. Simple questions are answered with complex stream-of-consciousness replies. 'I digress,' he says, after giving a lengthy description of a personnel manager at his last company, in response to a question about the marriage that ended. 'This is typical of an ADD-er.' Then he is up again, this time to turn off his computer, which is emitting a barely audible hum.

Stan's small office and sitting- room is upstairs, near Simon's bedroom. Through the walls we can hear the a cappella chorus of Queen's 'Bohemian Rhapsody'. 'He plays that song over and over again, but usually much louder. He kept us up till 2am last night - we're both pretty knackered.'

Stan is on Prozac; and if Simon stops taking the stimulant Ritalin, he starts to display what Linda describes as 'extraordinarily puzzling behaviour'. Often his mind fixes obsessively on one thought and he will repeat himself endlessly. 'He doesn't know why he's doing it,' she says. 'But he can't control himself.'

When Linda first met other Ladder members last year - at a talk given by Stan in Crawley, West Sussex - she was surprised how similar their behaviour seemed compared with her son's. 'One asked me a question. I began to reply and he just walked away,' she recalls. 'He came back five minutes later and just expected me to carry on.' Distractibility is so automatic that many sufferers have little perception of the effect their behaviour has on others. 'Their observations of people are somehow impaired.'

It comes as no surprise, perhaps, that the US, home of the three- minute culture and general technology overload, was the first country to recognise the syndrome in the early Eighties. One could be forgiven for confusing many sufferers with members of the much-publicised 'slacker' generation which, supposedly reared on an exclusive diet of MTV, Sega games and sound-bites, is permanently bored, listless and unable to defer gratification.

Yet many psychiatrists argue that sufferers are not simply a product of 20th-century technoculture. The cause is, they say, neurological. 'The part of the brain responsible for concentrating, focusing and restraining impulses is underactive in ADD people,' explains Stan. This particular brain imbalance can respond well to drugs such as Ritalin and some anti-depressants.

The condition is finally gaining recognition in Britain. Brian Toone, of King's College Hospital, is setting up one of the first clinics devoted to ADD sufferers. He says that the condition 'seems to be something that's constitutional. There may be some evidence that it runs in families'. A striking characteristic Dr Toone has observed is underachievement in relation to intelligence. 'People don't realise their full potential because of this handicap.'

Others close to the subject are more cynical. Craig Newnes, consultant clinical psychologist for Shropshire's Mental Health and NHS Trust, believes ADD is an example of psychiatric niche marketing. 'Most of these symptoms apply to all of us,' he says. 'It's based on people's desperate hope that just because you give something a name it has a meaning.'

Dr Newnes does not believe that ADD sufferers exist, at least not under one such convenient umbrella. 'If all these people came through my door, I would treat each of them on their individual merits. Their symptoms may not constitute a disorder but just a reaction to overwhelming distress.'

Ladder members disagree. Simon Smyth, 33, learnt about ADD through a distant relative in the US, who was told she suffered from the syndrome. 'My immediate reaction was, 'This sounds like a load of drivel - it's just another trendy syndrome.' ' But when he went to a library to read the self-diagnostic list of 21 ADD symptoms, Simon scored positive on every one.

'I still spend half my life walking into rooms and not knowing why,' he says. 'I know in my mind what I want to do, then something else crops up and I forget.' Even now he often leaves a sentence hanging in mid-air and continues at a slight tangent. 'I used to think I was a depressive, but when I discovered this I was . . .' He pauses to reflect. 'I can make allowances for myself. I know I'm getting things wrong because of ADD.'

Ladder now has 600 members and Stan has received more than 2,000 letters of inquiry. For sufferers, discovering their complaints are part of a recognised syndrome brings tremendous comfort and relief. 'I suddenly realised I wasn't a bad person,' says Stan. 'It took the responsibility away from me.'

Ben Smith, 30, agrees. 'Now I know that I have a problem, I can step back and look at myself.' Before he started taking medication, Ben's impulsiveness was uncontrollable - particularly where money was concerned. 'If I had a cheque book, I'd just spend and spend.' He has now closed his bank account and lives off cash.

According to Stan, many of these traits are shared by famous achievers in history. 'There's a lot of talk in the US about self-made men who were useless at school suffering from ADD - Thomas Edison, Leonardo da Vinci, even Mozart. We're usually very creative types.'

Linda nods encouragingly. She believes Stan will be famous one day for creating Ladder. 'I don't want to be arrogant, but I am getting there,' he says. 'At last I'm managing to turn my shortcomings into assets.'

Ladder, PO Box 700, Wolverhampton WV3 7YY.

(Photograph omitted)