Army researchers examined nearly 1,000 soldiers with a history of deployment-related concussion and found 20 percent had suffered the frequent headaches diagnosed as "chronic daily headache" for three months or more. Of those, a quarter literally had the headaches every day.

Concussion is considered a mild traumatic brain injury and is commonly followed by headaches. But little was understood about how many military personnel were experiencing the intense head pain daily -- or close to it -- for months on end.

"In general we know that chronic daily headache is itself one of the most debilitating forms of headache...and can sometimes be difficult to treat," said Major Brett Theeler, the study's lead author.

To gauge how widespread the problem is, Theeler, a doctor with the AMEDD Student Detachment, 187th Medical Battalion, Fort Sam Houston, Texas, and his colleagues surveyed 978 soldiers who had been deployed in Iraq or Afghanistan.

Each of the soldiers suffered a concussion while abroad, and nearly all of them - 98 percent - reported headaches afterward.

Twenty percent of the soldiers screened positive for chronic daily headache, while the rest had headaches on occasion.

Those whose headaches began within a week of their concussion were at greater risk for developing chronic daily headache as opposed to less frequent "episodic headaches."

A little more than half of the soldiers with chronic headaches reported that they started within a week of the concussion, compared to about a third of the soldiers who experienced episodic headaches.

The chronic headache group was also more likely to score higher on a test for signs of posttraumatic stress disorder (PTSD).

Nearly twice as many soldiers with chronic headache - 41 percent - screened positive for PTSD, compared to 18 percent of soldiers who did not experience headaches as often. Theeler said identifying these risk factors is important for trying to pinpoint soldiers who might be more likely to develop chronic daily headache so perhaps they could start headache treatment sooner.

It's not typical to treat soldiers to prevent headaches from becoming chronic, Theeler told Reuters Health.

And even if physicians could identify at-risk soldiers, "the problem is that there are no treatments proven to be effective in this setting," he added.

According to Dr. James Couch, a neurologist and professor at the University of Oklahoma Medical Center who was not involved in this study, the usual approach for treating headaches after a concussion is to use medications approved for other headache types, such as migraine.

"The effect is not 100 percent," he said. But most medicines are able to cut symptoms in half for about 60 percent of people, leaving a number of headache-sufferers who get little benefit from drugs.

Another possible option, Botox is approved to ease the symptoms of chronic migraines. The injections have not been tested for chronic headaches following concussion, but two-thirds of the soldiers in the study had migraine-like headaches, so the drug might help those.

Behavioral therapies can be useful as well, and Theeler said it's important to go for a multidisciplinary approach because the cause of the headaches is unknown.

In particular, the finding that more soldiers with chronic daily headache also had PTSD symptoms supports the idea that the headaches could be related to the actual physical brain injury, or to the psychological trauma of the event that caused the concussion.

"Head injury is actually a stressful event, independent of what happens to the brain," said Dr. Richard Lipton at the Albert Einstein School of Medicine in New York.

Lipton, who was not part of the current study, said he'd like to see whether the rates of chronic daily headache among members of the military are similar to those among civilians who have experienced a concussion.

"I don't know, but I would think, of people who live in a military context, in a heightened level of vigilance, it wouldn't be surprising if rates of both episodic and chronic headache were higher than in the civilian population," he speculated.

Although headaches after a concussion can be very debilitating for some people, the good news is they usually clear up in time.

Lipton told Reuters Health that studies of civilians show in most cases they will resolve on their own after a year or two. SOURCE: Headache, online March 8, 2012.

• A Permanent Economic Emergency