Ronald Reagan swore he had none. George W. Bush had a headful, and so did Bill Clinton -- of gray hairs, that is.
Now, President-elect Barack Obama, a day away from taking the nation's most demanding job, already shows a sprinkling of those pesky white streaks in his first official portrait, which was unveiled last week.
At 47, Obama is nearly a decade younger than his predecessor when he took the oath of office, and seems too cool and fit to let the looming presidency stress him out.
"The gray is coming quick," he reportedly said last July. "By the time I'm sworn in, I will look the part."
President Reagan famously denied that he ever dyed his lustrous locks. President Clinton's trademark shock of white followed him through two terms. And President Bush visibly aged from his first inaugural through the trauma of 9/11 and two unpopular wars.
Most medical experts say that genetics plays the largest role in determining when a person goes gray, but new research seems to back the old wive's tale that stress, indeed, can turn the head white, or at least gray. Some researchers say persistent mental or physical stress that lasts two or more years can cause premature aging of the hair.
The French say Marie Antoinette turned gray overnight when she awaited her fate with the guillotine -- a legend that at least one doctor said likely had a medical explanation. Anxiety may have made her hair temporarily fall out in a condition called telogen effluvium, leaving the pale villus -- or "baby hair" -- behind.
Longest Presidential Race in History
Obama's race for the White House was the longest in history -- nearly two years -- and many, such Dr. Anthony Gaspari, have noticed a graying around the president-elect's temples. And with an economic crisis and international conflicts at full throttle, more stress is on its way.
But, Gaspari said, "In Obama it looks genetic."
"There's a common garden variety graying of hair that is a gradual process from the death of cells on the hair follicle," Gaspari, a dermatologist from the University of Maryland Medical Center, told ABCNews.com.
Obama's 'Change:' His Hair
"Maybe when he was on the campaign trail he was dying his hair and now that he's elected he doesn't care so much or has less time or wants to look the distinguished leader mode, rather than the young upstart and man for change," he said.
But one researcher who has studied gray hair and its causes claims Americans are going gray five years earlier than they did in 1970 -- and probably because of stress.
"Basically, people gray as they grow older," said osteopath Tyler Cymet, vice president of medical education at the American Association of Colleges of Osteopathic Medicine who practices at Northwest Hospital outside Baltimore. And Obama is right on target, age-wise.
The average white male goes about 30 percent gray at the age of 34, "give or take nine years," Cymet told ABCNews.com. African-Americans hit the 30 percent gray mark at 44 years old, plus or minus 10 years.
After the head turns 30 percent gray, it is another two to seven years until a person is fully gray. About 50 percent of all people are graying by 50. Obama is three years away from that age.
White Mother, Black Father Affect Obama's Hair
"With President Obama having a white mother and an African-American father, he would fit in the middle of the two groups," Cymet said.
Hair color is determined genetically by the amount of melanin pigments produced by stem cells called melaocytes. There are two types of pigments: eumelanin (dark brown or black) and phaeomelanin (yellow blond to red).
At the end of the active phase of hair growth, the building blocks of hair in the follicle -- kerotincytes and melanocytes -- die. As you age, fewer melanocytes are replaced. New hairs growing from these follicles are depigmented and appear gray or white.
Stress can affect how quickly hair is shed, and the faster it regrows, the more quickly the pigment breaks down.
Cymet explains that hair growth comes in three phases -- growth, resting and breakdown in six-year cycles -- about seven to 15 cycles in a lifetime. When a person becomes highly stressed in the growth stage, that cycle could be reduced to two years.
"You have seven to 15 cycles of hair growth before you lose the color," Cymet said. "If you speed it up and go through the growth phase quickly by not sleeping or eating or high stress levels, like being president, it happens more quickly."
Stressed Presidents Show Early Gray
A variety of physical conditions can also cause the hair to whiten or fall out: autoimmune disorders, hypo- and hyperthyroidism and alopecia, rare genetic disorders, including piebaldism and Waardenburg syndrome, and even a vitamin B deficiency.
"But I don't think that's what our highly stressed leaders have," Cymet said.
Charles Figley, a psychologist who specializes in traumatic stress at Tulane University, told ABCNews.com that he's not worried that Obama's first white hairs signal health issues, but he does confirm that the presidency can take its toll.
'Hot Seat' of Presidency Takes Toll
"With excessive stress over time -- the four-year hot seat of the presidency -- cells can break down," he said.
Psychological stress is more apt to take a toll on a person's physical health than their hair color, according to Figley, yet the myths persist.
For Steve James, a New York City memoirist, his mother's story of her transformation during the London Blitz during World War II has grown to epic proportions.
"Mum said she went white overnight," he told ABCNews.com. "It was the bombing. She claimed it was the doodle bugs."
It was 1944 and his young mother lived with her parents while his father served with the British Royal Navy.
"Mum was sitting on the toilet upstairs and my grandmother, who had been bottling beets in the kitchen, was holding my baby sister," James said. "Mum claims she was thrown off the toilet and came running down to see the red juice all over the walls and thought they were both dead."
All survived, except his mother Olive's jet-black hair, or so the story goes.
"It was very traumatic and it seemed very plausible to me," he said. "But then, my mother was bit of a storyteller."
Figley does not dismiss the notion that this kind of stress could hasten the graying process.
"The physical environment can affect the brain, which affects our immune system," Figley said. "But stress is difficult to evaluate."
And presidents handle their stress differently. Obama is not a known worrier and seems to release his stress on the basketball court or in his daily gym workouts.
Barack Obama: 'Well-Balanced'
"This guy [Obama] is a well-balanced person who had to think on his feet," said Figley. "He hasn't had any handlers until more recently, and he's been forced to know how to address and manage stress."
And, said Figley, the president-elect is an optimist, a quality that studies show correlate with a long life expectancy.
"We're beginning to think that optimism is part of a very important trait -- ego resiliency that has been found to be highly correlated with positive effects," he said. "People can have terrible adversity, yet a buoyant attitude and their positive outlook doesn't change."
But hair stylists like Lee Kostu, who has seen hundreds of graying heads at Hair It Is salon in Robbinsville, N.J., is not totally convinced that it's all genetic, especially for those whose lives are stressful.
"Sometimes I see a little gray in a client and then they come back for the next cut and bam -- they're all white," he said.