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Consider the Season of Your Birth for What Ails You

June 30, 2008

If you’re celebrating a birthday this month, you’re more likely to be nearsighted than those born in the winter.

But if your birth date falls in February, March or April, the news is more distressing: Winter and early spring babies have a greater risk of developing schizophrenia than summer-born ones.

Strange coincidences? Esoteric astrological claims? Neither.

As unlikely as it sounds, a growing body of scientific research shows the month you were born can predispose you to certain traits, affecting everything from your personality and mental health to your lifespan.

Although there’s no empirical evidence showing a link between the signs of the zodiac and a person’s susceptibility to disease, Christopher Renstrom, author of “Ruling Planets” (Harper Collins, $18), reminds us that “astrology is a calendar that gave us the four seasons from which we derive the four temperaments: sanguine, choleric, melancholic and phlegmatic. Personality profiling comes from the zodiac. It’s the first form of it.”

The association between birth season and health, meanwhile, has been confirmed repeatedly by studies published in peer-reviewed journals.

It was first noticed with the neurological disorder schizophrenia; subsequent research has shown the month of birth can influence your risk of suicide and chance of developing certain cancers, Crohn’s disease, coronary heart disease and brain tumors, says psychiatrist Emad Salib of Peasley Cross Hospital in Britain, the lead author of a study in the British Journal of Psychiatry linking birth in late spring to suicide.

Literature reviews, meanwhile, show that more patients with schizophrenia, Alzheimer’s disease, epilepsy and narcolepsy are born in December and January. Those with affective disorders _ alcohol dependence, autism, dyslexia and multiple sclerosis _ are reported more frequently in those born during spring and summer months.

“The question for the research community is no longer, Does season of birth influence health outcomes?” said psychiatrist John McGrath of the University of Queensland, whose work has linked schizophrenia to winter birth dates in three- to four-year cycles. “We have known the answer to this question (is yes) for decades.”

What they don’t know is exactly how birth seasons affect mental health and disease. Unlocking this mystery is the next task for scientists who hope it will lead to new strategies for preventing serious illnesses and disorders.

A mother’s health is the root of several possible explanations. For instance, the fetal origins hypothesis holds that early environmental conditions in utero and during infancy can program human immune development. Some of these factors include a mother’s access to fresh vegetables or vitamins, or her exposure to an infectious disease such as influenza that might harm the brain of a developing fetus.

More recent research has centered on the star we’re all born under: the sun. The amount of sunshine a mother receives or the effects of temperature could affect her hormone levels, some scientists suggest.

Melatonin, a hormone secreted by the pineal gland in the brain in response to darkness, is suppressed by sunshine. Salib has speculated that having too much melatonin could trigger changes in the brain that increase a person’s chances of committing suicide later in life.

A lack of sunlight, which leads to low vitamin D levels, could be another factor. Sunlight stimulates the production of vitamin D, which fetuses need for brain development. But in many places, including Chicago, winter sunshine is in short supply.

“We have robust evidence that low prenatal vitamin D alters brain development and adult behavior in rats and mice,” said McGrath. “With respect to humans, the jury is out.”

Light exposure also can change the balance between dopamine and melatonin, said Israeli researcher Yossi Mandel and his colleagues, who showed that babies born in summer months had increased risks for moderate and severe myopia or nearsightedness.

The dopamine-melatonin balance “is known to participate in the eye-growth control mechanism,” Mandel said. “Altered eye growth pattern, such as larger eye length, can be associated with myopia.”

In some cases, though, the reasons might not be biological at all. Autumn-born children are about 9 percent more active than those born in the spring, according to a paper published in the British Medical Journal. But this is likely due to the age at which children start school, said lead researcher Calum Mattocks of the University of Bristol.

“Children born in autumn will tend to be the biggest, strongest and most developed in their school year,” he said. “So they are more likely to do better in sport, which may motivate them to stay active. Later born children may struggle to keep up, so they may get ‘turned off’ by games and exercise.”

Of course there will always be October-born people who are sedentary and June babies with perfect vision. Season of birth research is in its infancy, so it shouldn’t weigh into family-planning decisions.

But for women, increased vitamin D intake might be a way to counter negative effects of birth seasons, said Bruce Hollis, a professor of pediatric nutritional sciences at the Medical University of South Carolina.

“The amount of vitamin D in prenatal supplements is dangerously too low,” he said. “Every woman should take 2,000 units a day, and possibly more.”

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HEALTH RESEARCH FINDS NO ASTROLOGY LINK

Astrology, once regarded as a science, is nearly impossible to test in controlled laboratory conditions. That hasn’t stopped researchers _ most likely those curious Geminis and Virgos _ from trying.

One scientist investigated the link between Libras and renal disease. Nothing. And German researchers compared personality traits with the signs of the zodiac, only to find that astrology is popular with earthlings because “even modern people are inclined toward magical thinking.”

“Astrology is not religion, nor is it a science,” said astrologer Christopher Renstrom, author of “Ruling Planets” (HarperCollins, $18). “The key to understanding the seasonal temperaments is the planets, not the zodiac signs.”

In fact, people have identified with their zodiac sign only for the last century or so, Renstrom said. Before that, an Aries would have said, “I was born under Mars,”"Mars is my ruling planet” or “I’m a child of Mars.”

“Anyone born under Mars was considered hot under the collar, passionate and ready to get out and do,” Renstrom said. “Mars’ temperament is ‘sanguine’: easily aroused, excitable. This was connected to the spring season; Mars rules Aries, which is the sign of the spring equinox. Spring is all about beginnings and falling in love and pursuing anything new.”

And despite a lack of scientific credibility, plenty of people believe astrology holds clues to our health. Aries, Leos and Sagittarians, for example, are healthier than, say, Cancers, Pisces and Scorpios because “the first threesome are fire signs, which promise high energy and vitality; the other three are water signs, ever-changing, moody and drifting lifelong toward emotional and mental instability _ factors that affect health,” said astro-intuitive Albert Clayton Gaulden, founder of the Sedona Intensive, a life-coaching seminar.

If you believe in the power of the mind to heal, “the air signs Gemini, Libra and Aquarius have the capacity to will themselves to get well _ and to recover more quickly _ through the power of concentration,” said Gaulden. “And earth signs, Taurus, Virgo and Capricorn, are more akin to the earth itself,” which means they have a predisposition to health issues, he said.

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(c) 2008, Chicago Tribune.

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