(Health.com) -- Middle-aged women are roughly 40% more likely to become depressed if they experience migraine headaches, new research suggests.
What's more, their risk of depression appears to stay elevated even if the pain stops. Women whose migraines had not troubled them within the past year were just as likely to become depressed as women who were still enduring the sometimes crippling headaches, the study found.
"For women at least, migraine is a risk factor for depression," says lead author Tobias Kurth, M.D., an epidemiologist at Brigham and Women's Hospital, in Boston. "But there's no good biological reason why the link would not apply to men."
Kurth and his colleagues drew their data from the Women's Health Study, an ongoing survey of female health professionals that began in 1993. They examined the medical records of more than 36,000 women who had no history of depression at the start of the study. Roughly 18% of the women were experiencing some form of migraine or had suffered from the headaches in the past.
Over the next 14 years, 11% of the study participants received a depression diagnosis. Compared to women with no history of migraine, those who had ever had one were 36% more likely to become depressed. Women who used to get the headaches but were migraine-free in the year leading up to the study were 41% more likely to be diagnosed.
After taking into account the women's age, smoking and drinking habits, and other extenuating factors, the researchers found that the type of migraine did not influence depression risk.
Women whose headaches were preceded by flashing lights and other sensory disturbances -- a condition called migraine with aura, which occurs in 25% of migraine cases -- had the same risk of depression as women with the more common form of migraine.
Kurth is scheduled to present his findings at the annual meeting of the American Academy of Neurology in April. Neurologists and primary care physicians both should be aware of the relationship between depression and migraine, he says.
"If you know a patient may be more susceptible to symptoms of depression, you might ask questions," Kurth says. "You might follow them not just for their headaches, but be thinking about the link to depression so you can address symptoms early on."
The study's unusually long follow-up period is a strength, says neurologist Jason Rosenberg, M.D., director of the Johns Hopkins Headache Center, in Baltimore.
"It's been well-known that migraine and depression occur together much more commonly than can be explained by chance," says Rosenberg, who was not involved in the study. "This study gets us one step closer to establishing the link that migraine seems to precede depression."
On the other hand, Rosenberg says, the fact that all of the study participants were over the age of 45 does limit the findings somewhat. "Most women develop migraine when they are well under 40," he says. "An older population could skew the results one way or the other."
There is no clear explanation for the migraine-depression link. Although frequent migraines could usher in depression by reducing a person's quality of life, underlying -- and as yet unknown -- biological factors may play a role as well. In the future, Kurth says, scientists should try to identify brain chemicals that may contribute to both conditions.
"Are there common biomarkers in the neurotransmitters of the brain?" Kurth says. "I hope our research will stimulate targeted research that will look for mechanisms and figure out exactly what is going on."
Determining whether the frequency and severity of headaches influence the risk of depression will be another important piece of the puzzle, Rosenberg says.
Previous research suggests that depression risk rises along with migraine severity, Kurth says. He and his colleagues have not yet addressed that point, but they expect to in the future.
Copyright Health Magazine 2011