Although the medical community has not directly addressed a possible link between fibromyalgia and cluster headaches, there is a fair amount of research to suggest that common disturbances underly both diseases. Some of these include:

• Disturbed serotonin metabolism
• Low melatonin levels
• High levels of immune hormones including IL-1 and IL-6?
• Increased levels of mast cells, which release histamine and ohter inflammatory compounds.
• Magnesium deficiency is common in both conditions.
• Disturbed Prolactin secretion.

Fibromyalgia and cluster headaches are distinct conditions, and not everyone that has cluster headaches has fibromyalgia (and vice versa). But it is quite possible that there is significant overlap between the patient groups, and that having one may increase the chances that a person has the other.