Cluster Headache – One Of The Most Painful Conditions Known To Mankind

Cluster headache is a devastating and debilitating disease that affects approximately 7 million people worldwide. It is characterized by highly intense headache attacks which are usually located around one eye and can last for up to three hours. The attacks often occur in clusters, reappearing up to eight times daily during a period of weeks to months, and are then in a majority of patients followed by a symptom-free remission period lasting for months to years. The headache is accompanied by one or more autonomic symptoms, such as tearing, reddening of the eye, runny nose or nasal congestion, as well as restlessness.

The pain has been described as the worst pain known to mankind, and cluster headache has, in addition, received the notorious nickname “suicide headache” because of reports on suicide attempts to evade the pain when treatment is insufficient. The suicide rate for cluster headache patients is 20 times the national average. A global survey asked 1,500 cluster headache patients to rate cluster headache attacks and other painful conditions that they may have experienced on a scale from 1 to 10 and it could clearly be concluded that the pain of cluster headache stands out (9.7) compared to childbirth (7.2), kidney stones (6.6), migraine (5.4), or a gunshot wound (6.3).1

Many people have never heard of cluster headache, and there is still sometimes the misconception that headache disorders are psychosomatic. However, research has shown that there is a neurovascular basis to headaches which explains the pain and accompanying symptoms. Blood vessels in the head region dilate which stimulates pain receptors on nerve endings in close proximity and send a message to the brain that there is a pain in the head and/or face region. The causes for primary headaches (i.e. not caused by other conditions, such as head trauma or infection) have yet to be determined.

For cluster headache, several hypotheses have been proposed including a disturbance in circadian rhythm (circa= about; diem= day) in the affected. Many organisms, from bacteria to humans, are equipped with an endogenous biological clock which drives these 24-hour rhythms. This clock is very important to align our sleeping and feeding behavior to the light-dark cycle of the Earth. In a majority of cluster headache patients, the attacks follow a circadian pattern, meaning that their headache attacks reoccur at specific times of the day. Additionally, about half of the patients also exhibit circannual rhythmicity where the headache clusters reappear during specific times of the year.

In a paper published recently in Cephalalgia, our group has characterized the cluster headache population in Sweden.2 The patients completed a questionnaire regarding attack patterns, triggers, use of medications, and lifestyle factors. What is more, we developed a new severity index for grading cluster headache, the Cluster Headache Severity Scale (CHSS), in order to identify patients with a very high disease burden.

68% of the 500 cluster headache patients were men which supports the observation that the disorder is more common in men than in women.3 Disease onset is reported to be between 20 and 40 years of age, and, in the Swedish cohort, the average age at onset was 31 years. One out of ten patients stated having a close relative also diagnosed with cluster headache, indicating a hereditary component.

As previously mentioned, circadian rhythmicity may play a crucial role in cluster headache, and about two-thirds of Swedish cluster headache patients reported recurring headache attacks at specific times of the day. There is a clear peak of attacks during night time between 2:00 am and 4:00 am, whereas the lowest frequency of attacks occurs between 10:00 am and 2:00 pm. In addition, we saw that cluster headache patients with high CHSS scores reported fewer hours of sleep compared to patients with lower scores.

The most common trigger factor for headache attacks when in a cluster period is alcohol, as specified by more than half of the patients. Other common trigger factors that can provoke an attack during a cluster period are stress, weather (including heat, cold, and wind), specific foods or beverages, relaxation/sleep, or, on the contrary, sleep deprivation.

The most used successful abortive medication for cluster headache are triptans, such as sumatriptan, or oxygen, which both lead to a constriction of blood vessels, thereby easing the pain within 15 minutes. But, in particular, triptans are very unspecific, not to mention inefficient in around 30% of cluster headache patients, and cause a series of side effects such as head pain and nausea.

According to several studies, cluster headache patients smoke cigarettes more frequently than the general population. About 29% in our cohort were current smokers as compared to 12% of the general Swedish population. We identified a delayed disease onset in current or previous smokers with cluster headache compared to non-smokers, which could suggest that smoking is a type of self-medication for cluster headache due to its vasoconstrictive properties and thereby delaying disease onset.

Not surprisingly, alcohol consumption was identified to be much lower in cluster headache patients with a higher disease burden (high CHSS score), since alcohol is a common trigger factor. Women with cluster headache specify more often that they do not drink alcohol at all (47%) compared to women of the general Swedish population (18%).

This study characterizes the cluster headache population in Sweden and demonstrates how profoundly affected the daily lives of this patient group is. Headache disorders are still underappreciated by many healthcare systems according to the World Health Organization, although they produce high costs for the healthcare systems.4 More research needs to be done in this field in order to support this patient group and find more effective treatments.

These findings are described in the article entitled Cluster headache – clinical pattern and a new severity scale in a Swedish cohort, recently published in the journal Cephalalgia.


  1. Schor LI. Cluster Headache: Investigating severity of pain, suicidality, personal burden, access to effective treatment, and demographics among a large International survey sample. Cephalalgia. 2017;37:172
  2. Steinberg A, Fourier C, Ran C, et al. Cluster headache – clinical pattern and a new severity scale in a Swedish cohort. Cephalalgia. 2018;38:1286–1295
  3. Headache Classification Committee of the International Headache Society (IHS). The International Classification of Headache Disorders, 3rd edition. Cephalalgia. 2018;38:1–211
  4. Polson M, Lord TC, Evangelatos TM, et al. Real-world health plan claims analysis of differences in healthcare utilization and total cost in patients suffering from cluster headaches and those without headache-related conditions. Am J Manag Care. 2017;23:S295–S299

About The Author

Carmen Fourier

Camen Fourier is a graduate student at the Karolinska Institutet, affiliated with the Carmine Belin research group. Carmen studies the role of genetics and circadian rhythm in cluster headache.

Andrea Carmine Belin

Andrea Carmine Belin is a senior researcher and head of the Carmine Belin research group at the Karolinska Institutet.

The purpose of our research is to increase the understanding of the pathophysiology of neurological disorders with a focus on neurovascular disorders such as cluster headache by identifying, characterizing and modelling genetic markers within the human genome since genetic factors have been proposed as a causative role. We suggest that there are multiple genetic factors that combine in different ways to increase or decrease risk for disease. These factors need to be identified in order to begin unwinding the causative pathways leading to the different forms of the disorder. Knowledge about gene function and findings from linkage and genome-wide association studies are applied to clinical material (DNA and cell lines) and data collected from patients with cluster headache as well as neurologically healthy controls to decipher genetic factors.

Comments (5)

  1. Thank you for your wonderful research on cluster headaches.
    One of my patients sent this link to me. I am a chiropractor who treats patients for headaches, including cluster and migraine headaches. I originally became a chiropractor because I was treated by a Chiropractor who relieved me of my cluster headaches. I have not even begun to deliver the research on my own results with patients because headaches is just one of many symptoms my chiropractic approach and preventative care is helping manage and in some cases cure. Your research makes it very apparent that more research needs to also be driven by chiropractors to help support their intervention and treatment approach for cluster headache. The more patient choice for treatment is available the better for patients.
    Unlike conventional medicine, chiropractors don’t focus on the ‘conditions’, but rather we focus on an individual’s natural healing potential, and would apply this to any patient including those with cluster headache. Chiropractic both recognises and treats the less clinically obvious and unique structural imbalances that can develop at any stage during life and which can effect and suppress the nervous system and therefore the natural healing potential within us. There are 3 main imbalances (each with their own subdivisions) which cause stress to the nervous system, effecting our innate healing potential and resulting in pain (like that of cluster headache):
    1. Structural Imbalance (bone and muscle, especially the bones of the spine and skull)
    2. Emotional imbalance
    3. Chemical imbalance (commonly from nutritional imbalances).
    This makes the study and research of what we do complicated as it takes the approach of evaluating the ‘whole person’ and their lifestyle as well as making structural adjustments into account to obtain the best long term results for a patient. The intent of our structural adjusting is to release the individual’s own healing potential. For some individuals to have a full healing potential (even for those with cluster headache) structural intervention can be enough, but emotional and nutritional imbalances may also need to be addressed. Like a computer dealing with viruses, the brain only has a certain capacity of resources for dealing with all our human imbalances, and when it reaches it’s threshold, it crashes and there is pain released. Pain is a message that the body needs help. Where the pain is released is not often where the root cause is, it’s often a chain of events causing structural compensatory patterns, along with genetic factors (these may also be structural as well as neurovascular) which all have to be considered in order to get a good result for the individual. There is not one treatment that will suit all. A Chiropractic approach actually has a very broad way of approaching pain, and does not look to effect it from the outside in, but from the inside out, with a focus on finding a logical root cause of pain from within the persons own body, which can not be separated from the effects of emotion and lifestyle too. More to be done on the research for this subject of cluster headache.

  2. Thank you!
    They didn’t leave out the chronics, as some seems to think. 10 % of the mass were CCH. They are automatically included in the duration section > 7.

    Steinberg, A., Fourier, C., Ran, C., Waldenlind, E., Sjöstrand, C., & Belin, A. C. (2018). Cluster headache–clinical pattern and a new severity scale in a Swedish cohort. Cephalalgia, 38(7), 1286-1295.

  3. I am chronic as well.
    Thank you to everyone involved. There isn’t enough words of appreciation that I can convey.
    The multiple efforts in helping us Cluster patients has greatly increased since I was diagnosed back in 2016. I could hardly find any information helping me to understand what I have or would be dealing with. 30plys years of hell

  4. Awesome article on cluster headaches but they left out that there are some who are chronic and don’t get a remission period such as myself. I’ve had cluster headaches for 7yrs and have always been chronic.

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