This is information [below] Yahoo Health has listed on their website relating to Cluster Headaches:

YAHOO! HEALTH

Cluster headache Health Article

Causes, incidence, and risk factors
Cluster headaches are a fairly common form of chronic, repeated headaches.

["Fairly common"? Since when?]  :o

Prevention
If prone to cluster headache, stop smoking.

[Huh? Many CH sufferers have never smoked.]   ::)

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I do believe Yahoo needs to do some fact checking & corrections.