Women who currently experience migraines or who have suffered from them in the past may be at a greater risk for developing depression than those without migraines, according to a new study. It joins a growing body of literature linking the two conditions and attempting to better understand the possible connection.
"We don't want to scare patients, and we know that migraine sufferers suffer a lot because of the migraines themselves," said Dr. Tobias Kurth, a neuroepidemiologist at Brigham and Women's Hospital and one of the study's authors. "But this highlights the need [for doctors and patients] to talk about the possible risk of depression."
In the new study, which will be presented in April at the American Academy of Neurology's 64th annual meeting, researchers looked at more than 36,000 women who were enrolled in the Women's Health Study -- a trial designed, primarily, to evaluate the effects of vitamin E and aspirin in preventing cardiovascular disease and cancer in women.
At baseline, approximately one in six women indicated they had migraines or had experienced them in the past. None of the women said they had a history of depression. However, over an average of 14 years of follow-up, nearly 4,000 of the women developed depression.
Overall, the researchers estimate that women with migraines or a history of the severe headaches were approximately 40 percent more likely to develop depression than women without migraines.
Since the new research has not yet been published in a peer-reviewed journal, it should be regarded as preliminary. However, additional research has also linked migraines and depression.
Last fall, a study out of Calgary -- published in the journal Headache -- found "substantial evidence" that migraines are linked with subsequent development of major depressive episodes. It also found some confirmation that depressive episodes are associated with later migraines, but it was not a causal link. When the researchers took into account factors like stress and childhood trauma, that link disappeared.
The new presentation may help shed light on which condition typically comes first -- migraines or depression.
"This doesn't prove that migraine itself caused depression, but there certainly seems to be a strong link," said Dr. Jason Rosenberg, an assistant professor of neurology at Johns Hopkins Medicine, who was not associated with the research.
"What this adds is the order in which this tends to happen -- that migraines start first, which may predispose you to depression later," he continued.
Kurth explained that the current research cannot, and does not, indicate the mechanisms behind the seeming connection between migraines and depression.
It could be that because both migraines and depression relate to the brain, similar biological concepts are at play. For example, neurotransmitters that are responsible for one could also trigger the other. It may also be that migraines negatively impact people's mental health and happiness, possibly leading to depression, Kurth hypothesized.
"How it works is anybody's guess at this point," agreed Rosenberg, who stressed that co-occurrence does not necessarily indicate causality, or even linkage. "Is it chemical? Are people worn down and sad because they're getting these headaches? Is it something you're born with that's underlying both?"
As researchers attempt to address these questions, the current message may simply be that the possible connection should be on patients' and health care providers' radars.
"We can't advise anyone, 'Just don't get headaches,'" Rosenberg said. "But as a physician, it's good to be aware of this and maybe screen patients."