(CNN) -- Soon after Paul Coskie's bicycle collided with a car, it became clear to his mother that her son would be sick for a very long time, and indeed he was. The 13-year-old boy went into a coma for a month and spent six months total in the hospital.
What his mother didn't know at the time was that Paul's collision would eventually claim another victim -- one who was nowhere near the accident scene.
After taking care of her son for a year, Dixie Fremont-Smith Coskie started to lose her balance, stumbling at times when she walked. Then she became so weak she couldn't get out of bed.
"I had tingling down my arm and terrible pain in my neck," remembers Coskie, 50, who lives in Upton, Massachusetts. "I thought I had Lou Gehrig's disease, but was so frightened I couldn't even tell my husband."
After performing a battery of tests, her doctor concluded she didn't have Lou Gehrig's. What she had was a reaction to stress.
"The tingling in my arm and the pain in my neck -- the doctor explained it was because I had the weight of the world on my shoulders," says Coskie, who was also tending to the needs of her six other children while caring for Paul.
More than 65 million people -- nearly a third of the U.S. population, provide care for a friend or family member during any given year, according to the National Family Caregivers Association.
In an editorial in the May issue of the Journal of the American Geriatrics Society, psychologist Peter Vitaliano explains that many of these people suffer just as Coskie did.
"Thousands of articles have reported greater psychological and physical health problems in caregivers than in noncaregivers," writes Vitaliano, a professor in the department of psychiatry and behavioral sciences at the University of Washington School of Medicine.
In the same issue, a team led by researchers at the University of Utah studied 1,221 elderly married couples and found someone was six times more likely to develop dementia if his or her spouse had dementia.
It's not entirely clear why caregiving can make you sick, but researchers believe depression and chronically high levels of the stress hormone cortisol, both of which often accompany caregiving, take a toll on the body's immune and cardiovascular systems.
Coskie says she never dreamed stress could wreak such havoc on her body, but in retrospect it makes sense.
For six months, she and her husband, Steven, drove an hour back and forth from their home to Paul's hospital in Boston. Then after his discharge, she needed to feed, bathe and dress her son at home.
She says she didn't really feel the stress effects of Paul's accident until Paul was finally able to go back to school and the demands decreased. "My body just allowed itself to freak out," she says.
For tips on how to recognize when you're experiencing caregiver burnout, see this advice from the Cleveland Clinic.
Four months of physical therapy put her on the road to recovery, and Coskie didn't think much more about the physical effects of stress -- until she was forced to about two years later.
In 2005, Paul got a diagnosis of leukemia. Once again, she and her husband didn't know whether Paul would live or die. Once again, they took daily one-hour trips back and forth to Boston, where Paul spent three months at Children's Hospital receiving a bone marrow transplant. Then after he came home, the Coskies had to keep Paul's surroundings sterile because of his depleted immune system.
Plus, there was a new stress, one that wasn't there after the bike accident: in 2004, the couple had a baby, their eighth child.
"I knew what happened to me the first time, and this second time around I didn't want it to happen again," Coskie says. "My husband and I sat down and decided we needed to do things differently."
In her book, "Unthinkable," Coskie explains how she and her family minimized stress with Paul's second illness. Here are some of her tips, along with advice from experts on stress and caregiving.
1. Control the carbs
There's no question: Stress can make you fat, and being fat takes a toll on your health.
"Excess cortisol increases insulin, and that changes the way carbohydrates are metabolized," says Dr. Christiane Northrup, who writes about caregiving in "Women's Bodies, Women's Wisdom," a new edition of which is being released later this month.
"You crave sweets, and that's why every nurses' station I've ever seen has doughnuts and chocolate sitting around. Constant caregiving, so constant sugar cravings," she says.
Eating sweets may make you feel less stressed out temporarily. "Eating sugars and starches has an opiate-like effect on the brain," Northrup says. "It dulls the pain for a while."
But eventually (and obviously) a diet of doughnuts will make you gain weight. In his editorial, Vitaliano notes that caregivers had greater calorie and fat intake and were more likely to be obese compared to noncaregivers.
After Paul's leukemia diagnosis, his mother made a deliberate decision to eat better. "The first time, after his accident, I practically lived on coffee and junk food," Coskie remembers. "When he had cancer, I made sure I actually sat down and ate meals."
2. Get rid of the guilt
Guilt, like stress, can send your stress hormones skyrocketing, creating a double whammy, Northrup explains.
"I've had patients who felt so guilty about leaving their loved one they wouldn't even come in for their own annual exams," says Northrup, who practiced obstetrics and gynecology for 25 years.
Coskie remembers how after her son's accident she felt too guilty to do simple things such as go to the movies or take a walk.
"How could I possibly think about taking a walk on a beach to escape for a moment when my son could not even walk?" she says. "To feel joy or pleasure or any type of happiness while my son lay incapacitated on a hospital bed just did not feel right."
The University of California, San Francisco, has advice for caregivers -- see the section in Chapter Eight about allowing yourself to laugh.
3. Resist "helpless hopeless"
That's Northrup's term for feeling like you're stuck and no one can help.
"You should assume that help is available, but you just don't know what form it will take," she says.
When she was 8 years old, Northrup's baby brother, Bill, was born. He wouldn't eat, and at a year old weighed just 10 pounds. Northrup's mother exhausted herself caring for Bill and her four other children.
"He needed feedings every hour on the hour," Northrup remembers. "One day a woman named Edna appeared at our door and said, 'I heard you need help.' She had the same name and birthday as my mother."
Bill put out his arms and smiled at Edna, who spent years helping care for him.
The key here: Northrup's mother had been open with people in their community about her tough situation, which is how Edna knew she needed help.
Sometimes, it's hard to say "yes" to help, even when you need it most.
"People would say, 'What can I do?' and I'd think to myself, 'My God, there's 110 things you could do,' but I'd say 'Oh no, that's OK.' "
With Paul's second illness, Coskie made a deliberate decision to change her ways. "I let down my pride. I knew that if I tried to do this by myself, I'd collapse again," she says.
Coskie advises making a list of the things you need so you can have a quick answer when friends asked what they could do. "You might need help with baby-sitting or carpooling or bringing over a few necessities like milk or bread or eggs. Give them suggestions because they don't know what to do."
4. Reject "hamster head"
"Hamster head," according to psychologist David Coon, is when unhelpful thoughts, worries and anxieties go around and around in your mind.
"Write them down and think about positive thoughts you can replace them with," advises Coon, a professor in the college of nursing and health innovation at Arizona State University who studies caregiving for people with dementia.
"Instead of thinking, 'Dad's really going downhill,' think about a pleasant interchange you just had with Dad, or remind yourself how you're doing a great job creating a safe, caring environment for him," he says.
For more advice on caring for someone with dementia, see these strategies from the Family Caregiving Alliance and the National Institute on Aging.
5. "Surrender, Dorothy"
This one is for people who might have disagreements with a parent who needs care.
"Right now you have baby boomers caring for people in the World War II generation, and there's a huge generation gap, because boomers are much more likely to question a doctor's authority," Northrup says.
For example, a boomer might want a parent to try taking vitamins or some other form of alternative medicine, or to get a second opinion from another doctor, but the parent resists.
"It gets abrasive. It's like sandpaper," she says.
Northrup's solution: Don't argue with your parent. "It's like 'Surrender, Dorothy,' in 'The Wizard of Oz.' Just let it go," she says.
Today, Paul Coskie is 22. His leukemia went into remission and then returned in 2008. He's receiving daily chemotherapy and his speech is slow and his left side sometimes shakes from his head injury.
His mother's big lesson from her caregiving experience: Try to take time for yourself and meditate. "Be more aware of yourself," she says. "Be more conscious."
CNN's Sabriya Rice contributed to this report.