Why does it always rain on me?

Nick Morrison finds out why we feel under the weather.

ACCORDING to Pat Thomas, at least one in three of us is "weather sensitive". That's a pretty high proportion in anyone's book, but she says there is evidence to suggest the real figure is around seven in ten. Seven out of ten of us, that is, whose health is closely linked to the weather.

Of course, there are the obvious ailments: colds in winter; hay fever in summer. There are also those which are less well-understood but just as debilitating - Seasonal Affective Disorder (SAD) springs to mind. But Pat believes it goes much deeper than this. She says anything from schizophrenia to strokes, cancer to vertigo, fertility to heart attacks, can be directly related to the climate. Not to mention road rage.

"I read about some scientists in Canada looking at weather as one of the causes of migraine, and it struck me that there must be other things that weather interacts with," says Pat, an author and the editor of an alternative health newsletter.

"The more I read, the more I thought that this was big stuff, but it seemed to me that as modern science evolved, it has tended to exclude anything that we can't control and that is unpredictable."

Pat, who has set out her theories in a new book, says her research uncovered studies stretching back a century and more into the links between health and environment. One of the most widely-known, but frequently dismissed by doctors, is that some people can predict the weather with their joints. Pat says there are good reasons why this is true.

"When the barometer drops, our body tissues expand and put pressure on our joints. It is like the atmosphere bearing down on us like a giant elastic body stocking," she says. This squeezing, associated with low pressure and therefore colder weather, also causes insomnia, headaches and problems with concentration. But cold weather can bring on illness in other ways.

'IF it is very cold, the reason you might get a headache is because your blood vessels are contracting. Your body is withdrawing blood from the surface of your skin in order to keep you warm, that is why very cold temperatures can bring on a migraine.

"If you think of your body as a system that likes to stay stable, then if it is expanding very quickly or contracting very quickly, then you can experience headaches," Pat says.

Cold weather, particularly when accompanied by sharp drops in temperature, can also increase the risks of heart attacks and strokes, she says, as blood becomes thicker as the temperature drops, putting more pressure on the heart. "There is good evidence to show that winter does gel the blood to keep us warm, but for people who are prone to strokes or who have heart problems, that may not be a good thing. When the cold weather first hits, there are more people in hospital with heart attacks and strokes."

But the heat brings its own problems, leading the body to produce chemicals that impair judgement and reduce concentration, which is why the incidence of road rage rises during the summer, as does that of car accidents and of street crime. Hot, dry winds are said to increase anxiety and aggression.

"Some people seem to have a very low tolerance for winds, and after a while they become very stressful. One of the reasons is the friction of the wind against the skin. But also, when the winds are blowing there is a high level of positive ions - electrically charged particles - in the environment.

"They stimulate higher levels of serotonin, which is a feel-good chemical. The problem is, it needs to be finely balanced in our bodies, so when positive ions stimulate too much serotonin, you can end up with nausea or breathing problems. That is why wind can be wonderful on a hot day, but you can end up thinking you have got to get out of this wind."

The rise in temperatures also brings a summer version of SAD, where sufferers experience insomnia, anxiety, poor appetite and weight loss.

But if some of these ailments seem like natural reactions to extreme weather conditions, or sudden changes in climate, there are some more unusual ways in which our environment is said to affect our health. Babies born in February and March are ten per cent more likely to develop schizophrenia than babies born at other times of the year, and there is a theory that the condition is caused by a lack of sunlight during pregnancy.

Also, a higher incidence of prostate, breast and colon cancers across the more temperate regions of the United States - two to three times greater than in sunnier climes - has led some researchers to suggest that people living in cloudy or wintry conditions may be at greater risk of contracting the disease. Sunlight encourages the production of Vitamin D, which regulates the development of cells, and experiments have shown that it can block the spread of some cancer cells.

THERE has even been a study which suggests the season you are born can affect you long you live, finding that those born at the end of a year can live up to two-and-a-half years longer than people born between April and July.

Perhaps one of the most ancient links between health and climate is that between the weather and scar tissue. More than a thousand years ago, some cultures imposed an additional fine if a wound resulted in a weather sensitive scar.

"Scar tissue is different from normal skin tissue and it reacts differently to the environment," Pat says. "When the temperature rises, scar tissue can begin to tingle and itch, because it expands at a different rate to the skin around it. That is why people with scars can often predict the weather, because of the way the atmosphere changes."

But just because the weather is beyond our control, does not mean that we are completely at its mercy, and there are things we can do to minimise its effect on our health. "If we see ourselves as part of this natural environment, and we can predict when there might be extra stresses on our body, then we can take care. If you know how your body is going to react, then you can take your medicine early, so if you know you are more likely to get a migraine, you can do something about it," Pat says.

As many health problems are caused as much by changes in temperature as by the temperatures themselves, guarding against sudden drops or rises may be one solution, whether it is heating our homes less or donning more layers to protect against the cold. But however we decide to look at it, at least we know that if somebody says there are under the weather, they may really mean it.

* Under the Weather - How the Weather and Climate Affect Our Health, by Pat Thomas is published by Fusion Press, (£10.99).