There are three types of nightmare: those that apparently threaten one's survival, which usually means dreaming that somebody is trying to kill you; those that threaten your security, which could be your house being burnt down; and those that attack self-esteem, such as nightmares about failing exams, or being made fun of at work.
Most sufferers consider them too trivial a problem to take to a GP, and for those who do ask their doctor for help, the answer is usually unsatisfactory.
Fiona Holloway, 35, cannot remember a time when she did not have nightmares. She finally mentioned them to her doctor last year, when her husband said he could no longer stand being woken up by her screams.
'Of course, I didn't go to the doctor just about the nightmares, but since I was there anyhow, I asked if there was any solution. My GP said I could try sleeping tablets, but then there would be side effects. I didn't want to take drugs, so he said well, it's usually psychological and there's nothing one can do,' Mrs Holloway said.
Her mother, brother and sister all suffer from nightmares, although none of her three children has them. 'What annoys me,' said Mrs Holloway, 'is I wouldn't say I'm highly strung - you know, you look at some women, and you can say, she's neurotic, but that's not me. And lots of times, things are really hunky dory, but I'll get a bad spell of nightmares. Then other times, when I feel I'm under a great deal of stress, I'll sleep beautifully. I can't make any sense of it, and it's the same for the rest of the family.'
In Mrs Holloway's case, she will have been asleep for about an hour, when she suddenly wakes, convinced she is choking to death.
'I can laugh about it now in the daytime because I know it's stupid, but when it happens, even once I've woken up, and realise I'm awake, I still feel the life being squeezed out of me. It takes me about 15 minutes to recover.'
Mrs Holloway's brother, a strong man, has smashed windows and ripped bedding during nightmares. He had to pay a hotel for torn sheets when he stayed in Greece last summer.
Sharon Campbell, 28, has been having nightmares since she was six. Her first was about roses that turned into spiders around her. At 14, she started to dream about a man stabbing her from behind as she hid in a cupboard.
Last year Sharon tried taking milky drinks to stop her nightmares. That was when the dreams about the peeling skulls began.
In her nightmare, Mrs Campbell is in a villa she and her husband sometimes rent in the United States. Looking around the house, she sees it is lined with pipes lagged in sticky white bandages. Poking out of each pipe is a grapefruit shape covered with more white bandages. The bandages start to unfold, and out come peeled, rotting skulls. Mrs Campbell can smell the stench in her sleep. The couple barricade themselves into a room, but they can hear the skulls bashing around against the walls in the next room.
The day after a nightmare, Mrs Campbell is breathless and disorientated. She has managed to function despite her nightmares for most of her life, but she cannot deal with the rotting heads in the pipes. She has put on four stone in weight in the past two years, and has had to give up her job as personal assistant to a West End solicitor. She became too anxious to go on the London Underground. She also feels unable to have sexual intercourse. 'It's an impossibility for me right now, it's too close a thing to be doing.'
The definition of a nightmare is a frightening dream that wakes up the sleeper, and which the sleeper can remember. Nightmares are distinct from night terrors, which may cause sleepers to thrash about or scream, but which they don't remember on waking.
Mrs Campbell has never considered going to her GP for help. 'You know local GPs; it's all bunions and piles. I thought there would be no treatment, or else I'd have to see a psychoanalyst. I say to my husband, do you think I'm mad, and he says, don't worry, go back to sleep.'
Until this month, he was the only person to whom Mrs Campbell had described her nightmares. Then she and Mrs Holloway responded to an advertisement placed by Mary Burgess, a clinical nurse specialist at Bethlem Royal Hospital, Beckenham, Kent, who is challenging some of the accepted medical views on the problem of nightmares.
Ms Burgess has set up the Nightmare Research Group to locate sufferers and find out whether they can be treated at home using self-help techniques aimed at helping them to confront their fears and reduce anxiety.
Ms Burgess has had five hundred responses to her request for volunteers, from a wide range of people, including barristers and doctors. She is looking for people who have nightmares for no obvious reason - they are not taking medication, suffering from asthma or enduring major stress.
Ms Burgess says she is not operating a sleep laboratory and has no way of telling whether her respondents are describing their nightmares truthfully - though she questions whether anyone would bother to make them up.
But is it a good idea to 'cure' people's nightmares? Accepted wisdom is that nightmares are a form of release for emotions people cannot deal with during the day. Ms Burgess believes that there are people whose primary problem is having nightmares and their bad dreams are not a symptom of any other distress.
Arthur Crisp, professor of psychiatry at Atkinson Morley's Hospital, Wimbledon, which runs a sleep disorders clinic, disagrees. 'Nightmares relate to anxiety and conflict, or specific traumatic experiences. I would regard behavioural manipulation of nightmares as running the risk of displacing that anxiety into the daytime. When you dispel one symptom, that's when new ones appear,' says Professor Crisp.
Ms Burgess says her treatments may not help people who have other problems as well as nightmares. 'However, I'm a behavioural therapist, and behavioural methods have been shown to work with nightmare sufferers - and clearly people would prefer to treat their nightmares at home, rather than go to see a psychiatrist.'
Mrs Holloway said she wrote off to the Nightmare Research Group as soon as she read about it. So did Mrs Campbell.
Just having some recognition of their problem seems to be helping already. Mrs Holloway has had to fill out a chart for two weeks, giving her nightmares scores out of 10. 'Perhaps it's working already. I've had fewer nightmares since I started marking them.'
Mrs Campbell said she found it helpful just discussing her nightmares. 'Talking about this has made me think. We change house every eight months or so, because of my husband's job. And we go abroad six or eight times a year. As a child, we moved an awful lot, too. I must remember to tell Miss Burgess.'
Readers wishing to contact the Nightmare Research Group should send a large SAE with a 28p stamp to: Nightmare Research Group, Tyson West 2, Bethlem Royal Hospital, Monks Orchard Road, Beckenham, Kent BR3 3BX.Reuse content