Diseases In A Double-Pack: Genes Could Increase The Likelihood For Depression And Migraines

What do a migraine and depression have in common? Australian scientists unravel with the help of thousands of twins why both diseases frequently coincide.

Both happen inside the head, but many more commonalities may not show up at a first glance. They are just too different, the hammering headache of a migraine attack, and the leaden fog of melancholia. Yet there must be a connection between the two, which is what researchers believed after they found that both often coincide. People suffering from a migraine do develop depression with higher likelihood than healthy people. Vice versa, a similar association can be observed: nearly half of all people with a severe depression are also suffering from migraine-type headaches.

Where then is the connection? Does one of the diseases make people susceptible to the other? Or are certain life events, or special gene encodings, making some people vulnerable to both diseases? At least it is known that both are based on a genetic predisposition. Australian scientists have investigated this now in the so far largest twin study of this topic (1). Their summary: Certain genes can increase the disease likelihood for both disorders.

More than 10,000 twins aged 18 to 89 participated in the study by Yuanhao Yang, Dale Nyholt, and colleagues. Twin studies specifically allow scientists to assess what role genes and the environment may play. All twins were recruited from the Australian Twin Cohort. First, the scientists filtered all twins that were suffering or had suffered from depression or from a migraine headache. In both cases, they used special questionnaires and identified – at the very end – slightly more than 2,500 monozygotic and 2,900 dizygotic twin pairs for their analysis.

Heritability of a migraine was calculated to be 56 percent, for depression is was 42 percent. This implies that the environmental influence is higher in depression, while the genetic influence is higher in a migraine. This result fitted to older studies with a similar result. Subsequently, the researchers compared twin pains: are more monozygotic than dizygotic twins affected by both diseases, this result argues for a genetic origin, since monozygotic twins are genetically identical to 100%, while dizygotic twins only to 50%. And in fact, the differences between the types of twins underpin the notion of common genetic pathways that increase the risk for both depression and migraine. It does not seem that one disease increases the likelihood of the other, as the authors state.

A US-study of researchers with Ellen Schur as the first author came to similar results in 2010. They assumed that those genetic factors responsible for heritability of a migraine also account for 20% of the differences in depression (2). However, these researchers observed only the associations almost exclusively between migraines with aura and depressions.

The responsible genes are yet unknown. It is speculated, however, that genes encoding neurotransmission such as serotonin, dopamine or GABA in the brain may participate. Once these are identified, this may lead to novel management strategies for both diseases.

This is part 5 of a series covering twin health provided by Paul Enck from the Tübingen University Hospital and science writer Nicole Simon.

References:

1. Yang Y, Zhao H, Heath AC, Madden PA, Martin NG, Nyholt DR. Shared Genetic Factors Underlie Migraine and Depression. Twin Res Hum Genet. 2016 Jun 15:1-10.
2. Schur EA, Noonan C, Buchwald D, Goldberg J, Afari N. A twin study of depression and migraine: evidence for a shared genetic vulnerability. Headache 2009;49:1493-502.