Migraine and Other Health Conditions
Studies show that the prevalence of other health conditions, particularly depression, anxiety, insomnia, gastrointestinal issues, angina, epilepsy, and allergy, is higher amongst those with migraine and severe headache than the general population (17). These are referred to as ‘comorbidities’, meaning that people with one of the conditions are more likely to have one or more others as well. Recently, the migraine in America symptoms and treatment (MAST) study identified some of the most common comorbidities, surveying over 15,000 migraine patients and 77,000 controls (17). Extracts from this study and related studies on these comorbidities are included below.
Depression and anxiety
There have been studies linking migraine and psychiatric disorders dating back to 1990, when a study in Zürich found a strong association between migraine and depression (18). More recently, researchers found that migraine patients were two to three times as likely to have depression and more than three times as likely to have anxiety compared to the population (17, 19). This is heightened if a patient develops medication overuse headache, in which case they’re five or eight times as likely to develop depression or anxiety, respectively. While the root cause of this comorbidity still requires more research, psychiatric disorders and migraine share many biological, psychological and socio-environmental characteristics. Some key similarities are abnormal brain development and genetic traits, as well as the abnormal function of neurotransmitters and sex hormones, and stress (18).
The relationship between insomnia and migraine was long thought to be a result of cause and effect – for example, having a nocturnal migraine could disrupt one’s sleep. However, studies have shown that there is crossover in the underlying pathophysiology between these disorders. This includes the importance of common brain structures in both sleep and migraine (particularly the hypothalamus), and the involvement of some of the same neurotransmitters, neuropeptides and hormones (20). As a result, people with migraine are two to three times as likely to experience insomnia than people with no medical conditions (17, 21). Migraine is also comorbid with several other types of sleep disorders. Sleep performs important functions for the brain, and a lack of sleep may play a role in the progression of development of migraine (26).
Gastric ulcer/gastrointestinal bleeding
Patients with migraine are approximately three times more likely to have gastric ulcers, gastrointestinal (GI) bleeding or other GI disorders than the general population (17). There was also a direct correlation between the severity of migraine attacks, both in pain and headache days per month, and the likelihood of experiencing GI issues (17). Currently, the nature of this connection is unclear – whether there is an underlying shared pathophysiology, or if GI issues are a side effect of medication used by migraine patients. One study found that migraine patients with GI issues were also more likely to use opiates or barbiturates, so the link between GI conditions and medication is an area for future research (22).
Angina and other cardiovascular conditions
The MAST study found that the cardiovascular conditions that were most commonly comorbid with migraine were angina (reduced blood flow to the heart) and peripheral artery disease (PAD) (17). Both conditions were approximately twice as likely in migraine patients than the general population. However, another study found that there were differences between migraine subtypes – people who experience aura were three times more likely to have angina, while those without aura had a much lower risk (23). At this stage, there is no clear medical reason for the link between migraine and these conditions, other than the increased risk. Clinical advice for patients worried about vascular diseases is to avoid smoking, or medications that could impact cardiovascular function (23).
There have been a number of studies investigating the link between migraine and epilepsy, showing that migraine patients are more than twice as likely to have epilepsy than non-migraine controls (17). Both disorders involve neuronal excitability and changing electrical functions in the brain, such as the pattern of cortical spreading depression (a mechanism thought to cause aura symptoms). This is particularly evident in patients with familial hemiplegic migraine (FHM), as there are genetic overlaps in the neurotransmitter genes and ion channel genes in these two disorders (24).
Asthma and allergies
Many studies have shown the relationship between respiratory conditions and migraine, however the biological mechanisms causing this are still unclear. Some theories include genetic disposition, abnormal muscle function in blood vessels and airways, and mast cell activation (irregular immune system function). A notable feature of the link between respiratory issues and migraine is that the likelihood of comorbidity increases with headache days. One study found that migraine patients with fewer than 7 headache days per month were 1.5 times more likely to have hay fever, while those with 14 or more headache days were 2.6 times as likely to have hay fever (25). This trend was consistent for asthma and chronic bronchitis.