Adults and teenagers who suffered physical abuse as children may have a heightened risk of migraines, two new studies suggest.

In one study, Canadian researchers found that migraines were twice as common among adults with a history of childhood physical abuse compared to those who reported no such abuse.

Similarly, the second study, of nearly 4,000 Taiwanese teenagers, found a higher prevalence of migraine among those who said they had ever been beaten by a family member. And the more frequent the abuse, the greater the chances of suffering migraines.

Both studies, which appear in the journal Headache, point to an association between childhood physical abuse and migraine, but do not prove that abuse itself causes migraines in some people.

The exact reasons for the connection are not clear. The Canadian study found that factors such as chronic stress and mood disorders like depression seemed to partly explain the relationship, but did not fully account for it.

“I thought that mood disorders and stress might explain it away, but they didn’t,” lead researcher Dr. Esme Fuller-Thomson, of the University of Toronto, said in an interview. “There must be something else going on.”

She said that one possibility, based on laboratory research, has to do with the HPA axis - a component of the nervous system involved in the body’s response to stress, including levels of “stress hormones” like cortisol.

Studies have found that adults with a history of child abuse tend to show irregular patterns of HPA activation in response to stress, while people with migraines have been shown to have higher cortisol levels, on average, than people without the headaches.

That raises the possibility that abuse contributes to migraines by leading to dysfunction in the HPA axis.

Fuller-Thomson and her colleagues based their findings on data from a 2005 Canadian health survey. Of 13,000 respondents from that study, 7 percent said they had been physically abused as children.

Among adults who reported childhood abuse, 18 percent said they had been diagnosed with migraines. That compared with 9 percent of survey respondents who reported no past abuse.

The researchers then looked at a number of factors that could account for the abuse-migraine link. Those included “adverse childhood conditions” - like parents’ unemployment or drinking and drug use - as well as respondents’ own incomes and education levels, lifestyle habits, current stress levels and history of physical or mental health problems.

Many of those factors were linked to the risk of adulthood migraine and helped explain some of the relationship between physical abuse migraine. But even then, a history of abuse itself remained linked to a 36 percent greater risk of migraine.

In the Taiwanese study, researchers led by Dr. Jong-Ling Fuh, of Taipei Veterans General Hospital, evaluated headache symptoms and history of abuse among almost 4,000 13- to 15-year-olds.

Based on a standard questionnaire, the researchers diagnosed 23 percent of the teens with migraine or “probable” migraine. A similar percentage - 24 percent - said they had ever been “beaten” by a family member.

The researchers found that 30 percent of teenagers who reported such abuse had migraine symptoms, versus 21 percent of non-abused teens. What’s more, the more frequent the abuse, the greater the risk of migraine: the headaches were diagnosed in 28 percent of teenagers who said they had “rarely” been beaten, and in 38 percent of those who said they had “sometimes or often” been abused.

Fuller-Thomson pointed out that physical abuse is “just one of many factors” that may contribute to migraine risk. “I don’t want people with a history of abuse to think that they are destined to develop migraines,” she said.

It is important, however, for future studies to try to uncover the reasons for the connection between physical abuse and migraine, according to Fuller-Thomson. “If we know the mechanism, it might be possible to intervene,” she said.

For example, if post-traumatic stress disorder (PTSD) in response to abuse were a factor, then treating the PTSD with cognitive behavior therapy could conceivably lower the risk of future migraines. But that, Fuller-Thomson said, is just speculation for now.

SOURCE: Headache, March 2, 2010 online.