Migraine is one of the most common painful disorders afflicting one in every eight people. It is characterized by throbbing and relatively unpredictable episodes of head pain that may last up to three days.

Various studies have shown that patients with migraine have a higher frequency of depression and anxiety: a finding that will be unsurprising to most people that deal with pain. We could try to explain this as the psychological reaction to the pain and its unpredictability. Nevertheless, the link is deeper than that.

In fact, in a population-based study that followed patients for two years, the risk of major depression was six times higher in patients with migraine but this risk was not significantly increased for other severe headaches – this is a strong argument against the “psychological” explanation. Additionally, the risk of having a migraine was up to three times higher in patients with a major depression, while the risk of having other non-migraine severe headache was not increased.

If these findings seem surprising, things can even get weirder. Migraine and depression independently share one unexpected environmental risk factors: childhood emotional abuse.

So are there common pathophysiological mechanisms for both disorders? For instance, serotonin seems to have a role both in depression and migraine. And could we learn something on migraine studying depression and learn something on depression studying migraine? This is when things get interesting.

A recent study evaluated the relationship between allodynia and depression in migraine. Allodynia is the sensation of pain when faced with stimuli that are usually non-painful (e.g., pain from the touch of the hairbrush when combing your hair). Allodynia is a clinical hallmark of a process known as central sensitization: Due to a frequent, often repetitive stimulation of pain-sensitive neurons they increase their response to sensory stimuli.

This study found that migraineurs with allodynia had a significantly higher level of depressive symptoms when compared with those without allodynia. This association was independently of the number of monthly headache episodes, gender or any other patient characteristics. Additionally, the severity of the depressive symptoms seems to be associated with the severity of allodynia.

These authors hypothesizes that allodynia could be a link between depression and migraine. A psychological explanation cannot be excluded at the moment (e.g., patients with more “pain” due to non-painful stimuli will be more depressed) but, we also know that depression and allodynia are, in the long term, factors associated with an increase of the frequency of migraine episodes linking them even more.

Further studies with a long-term follow-up of patients will be necessary to clarify this relationship. In addition, studies comparing the neurophysiologic characteristics of allodynic depressed migraineurs and allodynic non-depressed migraineurs (or other combinations) would help us to know if the mechanisms of allodynia are shared with those of depression. This could pave the way for new treatments for both depression and migraine.

References

Breslau N, Lipton RB, Stewart WF, Schultz LR, & Welch KM (2003). Comorbidity of migraine and depression: investigating potential etiology and prognosis. Neurology, 60 (8), 1308-12 PMID: 12707434

Goulart AC, Santos IS, Brunoni AR, Nunes MA, Passos VM, Griep RH, Lotufo PA, & Benseñor IM (2014). Migraine headaches and mood/anxiety disorders in the ELSA Brazil. Headache, 54 (8), 1310-9 PMID: 24898830

Mendonça MD, Caetano A, Viana-Baptista M, & CHLO Headache Study Group (2015). Association of depressive symptoms with allodynia in patients with migraine: A cross-sectional study. Cephalalgia : an international journal of headache PMID: 26634832

Tietjen GE, Buse DC, Fanning KM, Serrano D, Reed ML, & Lipton RB (2015). Recalled maltreatment, migraine, and tension-type headache: results of the AMPP study. Neurology, 84 (2), 132-40 PMID: 25540306

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