School shootings, health scares, the roller coaster known as the stock market: Living in the '90s is enough to give anyone sweaty palms. While worrying is a natural response, says psychiatrist and Harvard Medical School instructor Edward Hallowell, it can easily spin out of control. Hallowell, author of the new book Worry: Hope and Help for a Common Condition (Ballantine Books), says that nearly half of Americans suffer from chronic worry—a condition that can he highly unpleasant, not to mention unhealthy. Don't fret. Most worriers, says Hallowell, can follow a few simple rules to rein in their anxieties and "learn how to worry well."

Hallowell (who cowrote Driven to Distraction, a 1994 bestseller about attention-deficit disorder) practices what he preaches. "I used to be one of those big-time worriers," admits the 48-year-old author, who lives in Arlington, Mass., with his wife, Sue, 42, a psychiatric social worker, and their three young children. "I'd stay up all night worrying about my kids, money, friendships." But by following the coping strategies he developed, he says, he has gotten his anxiety under control. "If you're a big worrier, you're never going to be a cool-as-a-cucumber type," he says, "but you can come out of that horrible toxic zone." Contributor Anne Driscoll talked with Hallowell at his Concord, Mass., office about why we worry, the dangers of worrying too much and how to worry wisely.

What is the difference between healthy and unhealthy worrying?

Good worry is worry that leads to constructive action. You make a plan. You set up an emergency cash reserve. Or you investigate that mole on your arm to see if it's cancerous. Toxic worry does just the opposite. It paralyzes you. You brood, you ruminate, you wake up in the middle of the night. Meanwhile you don't take action.

How can you tell if you worry too much?

Ask yourself some simple questions: "Do you worry a lot compared to your peers? What do you do with your worry?" If you say, "It's because of my worry that I'm successful," then that's fine. But if you say, "I get sick. I sit in a chair and stare ahead. I can't talk. I procrastinate. I underachieve. I get headaches, I get back pain, I get chest pain," that's toxic worry.

Why is it so dangerous?

Chronic worry is associated with a higher risk of heart attacks, elevated blood pressure, musculoskeletal aches and pains, gastrointestinal disturbances, ulcers, skin eruptions, eczema, asthma, respiratory problems and, ultimately, dying younger. I see excessive worry as a public health problem.

How many people worry excessively?

Almost one in four people, at some point in their lives, meet criteria for diagnosable anxiety disorders related to worry, such as obsessive-compulsive disorder. Those people need professional treatment. If you throw in all the everyday chronic worriers, then you're getting up to half the population.

Do people worry more today than they did in the past?

I think so. One reason is that people are disconnected. Family, neighborhoods, churches, all the structures that used to connect people—giving meaning and stability to their lives—have gradually broken down. People don't feel they're getting enough reassurance. They don't want to ask for it, they don't want to feel like crybabies, but they're not getting enough human moments. People are worrying alone, which is the worst way to worry.

What do people worry about most?

People tend to worry about their children the most. No. 2 is money. After that comes job security, relationships and health. You also get these waves of worries, like about the stock market or about fear of flying after the Swissair disaster. But for the real toxic worrier, times can be great, and they'll still find something to worry about. In fact when times are good, they'll worry more, because they'll think, "Uh-oh, what am I missing?"

Do men and women worry differently?

Men and women tend to worry about the same things and about the same amount, but it ends up hurting men more because they keep things bottled up, whereas women talk about it.

What do children worry about?

Adolescents worry about their personal appearance, their grades and achievement. Younger kids worry about personal security—robbers, kidnappers. The world has its dangers, for sure, but I think we have gone too far in telling 6-year-olds about rape, carnage, AIDS, war, disasters. Kids hear these stories and think it's going to happen to them tonight.

What steps can people take to control their worrying?

The most important rule is to never worry alone. It's very rare to get into a state of toxic worry when you're talking to someone. When you feel toxic worrying coming on, pick up the phone, walk into the next room, find a colleague, a spouse, a friend. Second, get the facts. Very often toxic worrying is based on a lack of information or on misinformation. You imagine that the boss disapproves of you, but you never actually go and ask him. Third, make a plan. Have a conversation with your boss about where you stand, and take steps to improve your performance in areas that need work.

What else can people do to reduce worry levels?

Exercise three times a week. It's great for your heart, but it's even better for your brain. When you exercise, your body generates a whole bunch of substances that go to your brain and rejuvenate it. It makes you less depressed and anxious. You can also use exercise at the moment you're getting worried. Just walk up the stairs a few times, or walk around the building. That little bit of exercise, as one of my patients puts it, "will push the reset button on your brain."

Prayer and meditation can also help push that reset button. I'm not trying to push religion on people, but some spiritual connection is helpful. You need to try, on a daily basis, to remind yourself of the larger perspective. We often imagine that the problem is much bigger than it actually is.

When should you get professional help?

Most everyday chronic worriers can use the steps I've outlined to bring their worry down into the normal range. But if you find that you're using all these steps and you're not getting much better, then you should see a doctor. And if you have an anxiety disorder, like obsessive-compulsive disorder or panic attacks, you need professional treatment.

What do you think about treating worry with drugs?

The availability of medications like Prozac and Zoloft is one of the big breakthroughs in the treatment of worry. They can change lives. I've seen it happen. I've seen people go from being scared, skittish and barely able to go outside to becoming company managers, to getting married or being in successful relationships. Used and prescribed properly, these drugs are a godsend.

Are there any treatments aside from medication?

Cognitive behavior psychotherapy can be very effective. It trains you to talk to yourself in a way that's more helpful, less negative. Some people are just awful to themselves. They walk into a meeting thinking, "You're ugly, you're stupid, you're fat, you're boring" and expect to do a good job. Cognitive therapy helps you learn to say to yourself, "I may not be the greatest person in the world, but I'm a decent one, and I'm going to do my best." It helps people get over their phobias and anxieties.

Is there such a thing as worrying too little?

You shouldn't want to get rid of worry completely. We call that denial. If you don't worry at all, you'll take foolish risks and get into trouble. As one of my friends says, "If you don't want to worry, be a plant."