Hormone levels - and hence our
moods –may be affected by the weather. Gloomy weather can cause depression,
but sunshine appears to raise the spirits. In Britain, for example, the
dull weather of winter drastically cuts down the amount of sunlight that is
experienced which strongly affects some people. They become so depressed
and lacking in energy that their work and social life are affected. This
condition has been given the name SAD (Seasonal Affective Disorder).
Sufferers can fight back by making the most of any sunlight in winter and
by spending a few hours each day under special, full-spectrum lamps. These
provide more ultraviolet and blue-green light than ordinary fluorescent and
tungsten lights. Some Russian scientists claim that children learn better
after being exposed to ultraviolet light. In warm countries, hours of work
are often arranged so that workers can take a break, or even a siesta,
during the hottest part of the day. Scientists are working to discover the
links between the weather and human beings’ moods and performance.
It is generally believed that
tempers grow shorter in hot, muggy weather. There is no doubt that ‘crimes
against the person’ rise in the summer, when the weather is hotter and fall
in the winter when the weather is colder. Research in the United States has
shown a relationship between temperature and street riots. The frequency of
riots rises dramatically as the weather gets warmer, hitting a peak around
27-30°C. But is this effect really due to a mood change caused by the heat?
Some scientists argue that trouble starts more often in hot weather merely
because there are more people in the street when the weather is good.
Psychologists have also
studied how being cold affects performance. Researchers compared divers
working in icy cold water at 5°C with others in water at 20°C (about swimming
pool temperature). The colder water made the divers worse at simple
arithmetic and other mental tasks. But significantly, their performance was
impaired as soon as they were put into the cold water – before their bodies
had time to cool down. This suggests that the low temperature did not slow
down mental functioning directly, but the feeling of cold distracted the
divers from their tasks.
Psychologists have conducted
studies showing that people become less skeptical and more optimistic when
the weather is sunny However, this apparently does not just depend on the
temperature. An American psychologist studied customers in a
temperature-controlled restaurant. They gave bigger tips when the sun was
shining and smaller tips when it wasn’t, even though the temperature in the
restaurant was the same. A link between weather and mood is made believable
by the evidence for a connection between behavior and the length of the
daylight hours. This, in turn, might involve the level of a hormone called
melatonin, produced in the pineal gland in the brain. The amount of
melatonin falls with greater exposure to daylight. Research shows that
melatonin plays an important part in the seasonal behavior of certain
animals. For example, food consumption of stags increases during the
winter, reaching a peak in February/ March. It falls again to a low point
in May, then rises to a peak in September, before dropping to another
minimum in November. These changes seem to be triggered by varying
melatonin levels.
In the laboratory, hamsters
put on more weight when the nights are getting shorter and their melatonin
levels are falling. On the other hand, if they are given injections of
melatonin, they will stop eating altogether. It seems that time cues
provided by the changing lengths of day and night trigger changes in
animals’ behavior - changes that are needed to cope with the cycle of the
seasons. People’s moods too, have been shown to react to the length of the
daylight hours. Skeptics might say that longer exposure to sunshine puts
people in a better mood because they associate it with the happy feelings
of holidays and freedom from responsibility. However, the belief that rain
and murky weather make people more unhappy is borne out by a study in
Belgium, which showed that a telephone counseling service gets more
telephone calls from people with suicidal feelings when it rains.
When there is a thunderstorm
brewing, some people complain of the air being ‘heavy’ and of feeling
irritable, moody and on edge. They may be reacting to the fact that the air
can become slightly positively charged when large thunderclouds are
generating the intense electrical fields that cause lightning flashes. The
positive charge increases the levels of serotonin (a chemical involved in
sending signals in the nervous system). High levels of serotonin in certain
areas of the nervous system make people more active and reactive and,
possibly, more aggressive. When certain winds are blowing, such as the
Mistral in southern France and the Fohn in southern Germany, mood can be
affected - and the number of traffic accidents rises. It may be significant
that the concentration of positively charged particles is greater than
normal in these winds. In the United Kingdom, 400,000 ionizers are sold
every year. These small machines raise the number of negative ions in the
air in a room. Many people claim they feel better in negatively charged
air.
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