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Spring Fever Disease?
Our biological clocks are closely associated with our perception of the
seasons, and our survival mechanisms within controlled by the pineal
gland and hypothalamus control center.
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Fact or Fiction?: 'Spring Fever' Is a Real Phenomenon
22 March 2007 - By Christie Nicholson - sciam.com
Is it salvation from winter that puts us in the mood for
love or is there a biological basis for this flurry of psychological
renewal and physical energy?
There's an illness that has been documented by poets for centuries.
Its symptoms include a flushed face, increased heart rate, appetite
loss, restlessness and daydreaming. It's spring fever, that
wonderfully amorphous disease we all recognize come April and May.
"Spring fever is not a definitive diagnostic category," says Michael
Terman, director of the Center for Light Treatment and Biological
Rhythms at Columbia University Medical Center. "But I would say it
begins as a rapid and yet unpredictable fluctuating mood and energy
state that contrasts with the relative low [of the] winter months that
precede it."
Such spring fever remains a fuzzy medical category, but there has been
a great deal of research on how seasonal changes affect our mood and
behavior. Matthew Keller, postdoctoral fellow at the Virginia
Institute for Psychiatric and Behavioral Genetics in Richmond, studied
500 people in the U.S. and Canada and found that the more time people
spent outside on a sunny spring day the better their mood. Such good
moods decreased during the hotter summer months and there is an
optimal temperature for them, Keller claims: 72 degrees Fahrenheit,
otherwise known as room temperature.
Of course, spring doesn't just lighten our mood; as Alfred Lord
Tennyson described, "In the spring a young man's fancy lightly turns
to thoughts of love." Studies show that sexual behavior in mammals
follows a seasonal pattern, one that promotes survival. In fact,
researchers discovered that birth spikes in field mice are more
significant the farther the mice are from the equator, as seasons
become more pronounced. The same trend was also seen in hares and
deer, according to Mammalian Reproductive Biology by biologist Frank
Bronson of the University of Texas. It is well documented that animals
and humans track seasons by measuring the length of days through an
internal biological clock, and this is what controls their breeding.
The biological clock, called the suprachiasmatic nucleus (SCN), sits
in mammals' hypothalamus. It monitors light through a pathway to the
retina and conveys information about day length to the pineal gland.
This pea-size gland, tucked at the base of the cerebrum, controls the
secretion of melatonin, dubbed the sleep hormone because it is only
released in the dark or in dim light. The duration of melatonin
release changes with nocturnal length, which is longest during winter.
And it has been thought that our increased energy in the spring months
is somehow linked to the decreased duration of melatonin production,
due to shorter nights.
"From a biological perspective, most types of animals, and maybe even
plants, have seasonal variation in behavior and physiology; there are
seasonal cycles in human rates of conception," says Thomas Wehr of the
National Institute of Mental Health, who reviewed the effect of
biological rhythms on reproduction in 2001 for the Journal of
Biological Rhythms. Historically there have been more births in the
spring. In the late 16th century birth rates typically spiked to 20
percent above the average in March—meaning the babies were conceived
in June—but over the past 400 years rates have flattened to about 10
percent above the average, according to research done by David Lam at
the University of Michigan's Population Studies Center in Ann Arbor.
Cultural and social factors influence conception patterns but biology
plays a strong role, as shown by peaks that are 20 percent above
average during June—technically the tail end of spring—in the
production of reproductive fuel: luteinizing hormone, which produces
testosterone in men and triggers ovulation in women. Research also
shows that successful in vitro fertilization follows the same seasonal
peaks as natural birth. "In humans we don't know for sure what the
causal connection is," Wehr says, "but if most other mammals are using
changes in day length, then the melatonin signal and conception rates
is a pretty plausible relationship, but more research is needed."
The idea that melatonin triggers our mood change in the spring is
"too convenient an explanation," Terman counters. "Melatonin is
more like the hands of the clock, it's not the essential variable."
Since the mid-1980s researchers have focused on the seasonal effect on
moods, with the emergence of a diagnostic label for winter depression,
seasonal affective disorder (SAD). No one knows the exact cause
of SAD, Terman says, but there are distinct patterns of winter
depression lifting in the spring. And the key for that rise in mood,
he argues, is the earlier onset of morning light. He has shown that
there is more depression on the western edges of time zones in the
U.S., where the sun rises later.
Clearly, there are marked correlations between moods, behavior and the
lengthening days of spring, but the precise cause for our renewed
energy remains elusive. The evidence for spring fever remains largely
anecdotal. But, just as SAD has proved sadly real, spring fever edges
away from science fiction, even if it is not quite science fact. |
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The
The
Labors in the Spirits of
Science
Living on the Lost Planet 
