Tension headaches affect about 40 percent of us every year, and they're often blamed on stress or muscle tension around the neck, back and shoulder area. But new research finds a different cause.

According to CBS News Medical Correspondent Dr. Jennifer Ashton, there are a lot of different types of headaches.

"One of the most important things is the location of the headache. When you're talking about a tension headache ... imagine a gripping, squeezing band of pain or pressure around the top or back of your head, very different than a migraine, a migraine headache tends to affect one side of the head. Sometimes one side of the face. Compare that to a cluster headache, which is really searing pain, usually behind one eye. So really, location is very important. (So are) severity and how often you get these headaches," she tells "Early Show" co-anchor Chris Wragge.

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While many might assume tension headaches are only caused by increased tension in the neck or shoulder area and upper back, the new research says that may not necessarily be the case.

Ashton observes that, "Just the name might, in fact, be a misnomer, because we would all have tension and stress headaches almost on a daily basis. The new thinking is that there's an increased activation in the pain sensor in the brain that then propagates or spreads pain throughout the head, and then involves the muscles in the back of the neck and shoulders. It used to be the other way around. We used to think that the pain actually started in the muscles, and then went to the head."

If it's not tension, what are some of the triggers that bring on tension headaches?

"It really is individual. When my patients come to me and tell me they have headaches, the first goal is really finding out what is their particular trigger," Ashton explains. "It could be hormonal or menstrual migraines. It could be inadequate sleep. We talk about sleep here all the time. It could be emotional distress, depression or anxiety. And then you go to things like caffeine, which can be a treatment. Caffeine withdrawal can cause a headache. Hunger, or dehydration, and overexertion. Whether that's physical or emotional. All of those things can trigger a tension headache."

Inadequate sleep always seems to be associated with health issues.

"Absolutely. A lot of consequences," Ashton stresses.

So what can we do to alleviate some of the stress headaches besides just taking two aspirin?

"The first thing is obviously knowing what triggers your particular headache. Then when you talk about treatments, most people will go for the over-the-counter remedies first -- things like ibuprofen or acetaminophen can be very effective. But interestingly and ironically, if you take too much of them, you can have a rebound phenomenon to cause the pain and bring on the headache," Ashton says. "Then you can go to prescription pain medications. (There's a) variety of classes of medications that doctors, we can write prescriptions for people who really suffer and are debilitated. But then lifestyle modification, things like yoga, acupuncture, exercise, can all be important. As can just good hydration. A lot of headaches are brought on by dehydration."

Not all headaches are created equal. But some headaches can be a harbinger of worse things that are going on inside your body, Wragge points out.

"Correct. And really in medicine, we don't want to dismiss the potentially life-threatening headache by chalking it off to something like a tension headache," Ashton adds. "In fact, people will come into the emergency room and say, 'I'm having the worst headache of my life.' Things that you should not ignore are a sudden headache that is different in quality or caliber than anything you've had before. Pain after an injury to the head. Any change in your vision, or numbness in your face. Or nausea or in-coordination, or obviously a loss of consciousness or confusion, you want to get to an emergency room immediately. Those can be serious."