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Tyra Banks says the stress from writing her new book gave her alopecia. What's behind the link between stress and hair loss?

Tyra Banks definitely has a lot on her plate, but she recently complained about having much less on her pate. The "supermodel-turned-mogul" just added "fiction writer" and "New York Times bestselling author" to her ever-growing list of accomplishments.

But banging out a book and running a multimillion dollar beauty, fashion, and entertainment empire reportedly took a toll on her in an unexpected place -- her scalp.

Banks let her hair down in a recent Wall Street Journal interview, confessing, "I got a little alopecia from the stress." The stress is the five years it took to write her newly released young-adult book, "Modelland" while juggling her other professional responsibilities. Banks prefaced her comment by admitting, "How can I say this without tearing up?"

We feel her pain, even though we suspect she could afford to hire a ghost writer to pen the pages.

Even so, losing the hair on your head -- whether it's temporarily or permanently -- is hard to do, even for the most beautiful and richest among us.

"Writing a book can definitely be a stressor that can lead to hair loss, or alopecia" says Orr Barak, MD, a dermatologist at Main Line Dermatology in Philadelphia. But in women with hair loss, doctors also have to rule out if the stressor is a thyroid problem or low iron levels. "While these are rarely the causes, it's more commonly an emotional stressor like Tyra is talking about," he points out.

Barak suspects Banks had "telogen effluvium," a kind of stress-induced hair loss.

Still, we needed to get to the root of her problem. Our "mane" question (sorry) was: Why does stress cause your tresses to fall out?

As Barak explains it, a normal head of hair spends 80 percent to 90 percent of its time in the growing phase of the hair cycle, known as anagen, and 10 percent to 20 percent of its time in the resting, or telogen, phase. (An exception to this is pregnancy when the hair cycle increases to 100 percent anagen, or growth.)

"When the body undergoes a stressor, the hair follicle is affected and a new equilibrium is set for the hair cycle," Barak says. The rate may fall to say, 60 percent of its time in the growing cycle and 40 percent in the resting phase. This down shift causes more hair to fall out, and you see more of it in your brush or shower drain.

Thankfully, shedding more hair than usual is often temporary. "When the body recovers from stress, hair will get back up to its normal 80 percent to 90 percent ratio of growth over time," notes Barak. We hope that's what happened to Bank's locks.

Have you noticed more hair loss during an especially stressful time? 

Related:

• Can hair really turn white from fright?
• Science of the silver fox: Why hair goes gray
• Your hair knows when you're about to have a heart attack

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