'Mummy, can you lay the table this way from now on please?'

It is natural for children to go through a 'tidy' stage, where careful routine takes over from chaos. But what if these rituals become compulsive? Catriona Wrottesley on our growing awareness of OCD in the young

Young children and anarchic mess belong together. Right? Well, not necessarily. Actually, plenty of under-fives exhibit a zeal for tidiness that puts their parents in the shade. A bossy insistence that mummy's shoes must go in their proper place and every single toy car or soft toy has to be lined up just so before settling down for the night marks a fairly unremarkable phase that many children go through.

Eventually, most will move on to the equally ordinary messiness of later childhood. Yet, there are those for whom the necessity for order and routine becomes a distressing compulsion.

Last weekend, about 500 sufferers of Obsessive Compulsive Disorder (OCD) converged at Imperial College London for the 2002 Obsessive Action Conference, where leading OCD expert, child psychiatrist Dr Isobel Heyman of the Maudsley Hospital and Institute of Psychiatry, highlighted evidence of how much early detection and treatment improves outcome. "Every attempt should be made to diagnose and treat as soon as possible," she says.

Because of the embarrassment that surrounds this distressing condition, many keep their rituals secret. But some 50 per cent of OCD sufferers begin their checking, touching, counting or washing routines in childhood. Dr Heyman estimates that around 1 per cent of all children have OCD.

And it's nobody's fault. "It doesn't respect race, class, IQ, early experiences or family style," says Dr Heyman. "OCD is due to a chemical imbalance in the brain. Sometimes an infection triggers the OCD. In most cases it's caused by a combination of genetic predisposition and either a specific event or stress."

Alison Bishop, 21, a student at Leeds University, first showed signs of OCD at 10. Her mother Lynne, 51, an accounting technician from Cleveland, links it to the stress of tests during Alison's final year of junior school.

Before writing anything, Alison had to touch the paper or squeeze her pen a certain number of times. "I always had to end on an even number. Same with opening and shutting drawers – I'd have to do it four times. If I didn't I was sure something dreadful would happen to my mum and dad."

Bedtime rituals lasted up to three hours, remembers Lynne. Alison had to lie in her bed in a certain way, always exactly the same position every night. For up to an hour, she would be engaged in a mind exercise to line up shapes symmetrically in her head.

If Lynne spoke, she would have to begin again. "I had to stay with her while she went through it. Then she would say, 'Night night, God bless, love you', anything from four to 10 times. I'd have to say it back exactly the right way or we'd have to start again. I soon learned not to get impatient. Getting cross prolonged the routine. If I let her do her rituals, I'd get downstairs quicker."

Five weeks into the first term at secondary school, Alison's anxiety grew so bad that Lynne went to her GP for help. Alison was referred to a psychiatrist, who prescribed the antidepressant Seroxat. Within days, her rituals and anxieties had subsided. "The effect was dramatic. From being near the bottom of the French class, she was coming in the top four in tests." Alison kept taking the medication until she was 16, when she decided to wean herself off after GCSEs. "She's been fine ever since," says Lynne.

Certain rituals are a part of normal childhood development. "It is quite usual for children to use ritualised behaviour as a way of keeping control over the world, particularly when they experience strong emotions such as anxiety and anger," explains Ann Horne, a child psychotherapist at the Portman Clinic in London. "You can see it in a number of children's games that include an element of superstition, like avoiding cracks in the pavement."

Equally, she says, a small child who appears to be obsessively tidying up may well be identifying with the mother in a positive way. "It is a rehearsal for being an adult," says Dr Horne. However, certain rituals can indicate distress in a child. "Tidying may also be a means of achieving order, to feel safe when the child is feeling things are on the edge of chaos."

Encouraging a child to talk about his or her anxieties can help, she says. "If he's worried by his parents arguing, for example. You can explain how sometimes people do have disagreements. Putting things into words makes feelings more manageable. Then there's less need for rituals."

But where does a normal response to stress end and OCD begin? This is a particularly difficult question given that children may be secretive about the difficulty and hide their habits. "The child is aware the rituals are unnecessary and don't make sense," says Dr Heyman. Yet early detection can be crucial: according to Dr Heyman, key indicators are whether the rituals or thoughts upset the child; whether they take more than an hour a day; and whether they interfere with the child's everyday life, at school or with friends.

Sarah, 49, a social worker from London, and her husband Peter, 48, an accountant, have spent the past eight years struggling to cope with their son Matthew's OCD. It began aged seven when he was due to give a magic show for his five-year-old sister's birthday party. As guests arrived, he stood at the front door and insisted they leave their shoes outside because they were "contaminated". The problem quickly escalated into four-hour bathing rituals and three-hour handwashing sessions at the sink after school.

Eventually he was referred for psychiatric help but things continued to deteriorate. "By 14, his contamination fears were so out of control, he couldn't manage at school any more," says Sarah. "Last November, I said to his psychiatrist we couldn't cope. The stress was making our 12-year-old daughter ill. If we didn't get help, we'd all end up in hospital."

Matthew was admitted as an in-patient at an adolescent mental health unit. When taken off medication for assessment, his washing rituals lasted 24 hours. "But with treatment, he has made enormous strides," says Sarah.

The good news is that around 70 per cent of cases of OCD are responsive to treatment. One method is cognitive behavioural therapy, which involves helping the patient and their family to learn – in manageable stages – how to resist repetitive rituals, and at the same time tolerate the temporary increase in anxiety this causes. The other is use of anti-depressants, especially SSRIs (selective serotonin reuptake inhibitors) such as Seroxat and Prozac.

Matthew returned to live at home last month. He takes Prozac and attends a special educational unit for lessons. "His confidence has grown and he copes much better socially," says Sarah. "He still has his rituals, but they're more manageable and don't involve other people."

She adds: "Part of the difficulty is that he doesn't really want to give them up. He's done them so long, they feel part of him."

Obsessive Action: 020 7226 4000 (Tues, Wed, Thurs, 10am-4pm); No Panic: Freephone 0808 8080545 (10am-10pm)