Certainly many migraine patients report using no caffeine, yet there is no demonstrated example of migraine absent caffeine use. Caffeine use cannot be ruled out by merely interviewing the patient, as the patient may be mistaken. Caffeine abstinence has never been verified in a migraine patient, which means it may be all migraine patients who report using no caffeine are mistaken.

The prevailing view of migraine pathogenesis should be based on demonstrated evidence, not on faith.

The honesty and intelligence of migraine patients is not in question, as honest and intelligent people can unknowingly consume caffeine.

Difficulty in this context has a precise meaning: it is the ratio of attempts to successes. Nobody knows what percentage of migraine patients who attempt caffeine abstinence fail, or how often migraine patients who report using no caffeine are mistaken. It may be all migraine patients use caffeine, knowingly or unknowingly.

Nobody knows how likely or unlikely it is. Given that migraine has never been demonstrated absent caffeine use, the possibility that all migraine is caffeine withdrawal headache is no less likely than the prevailing assumption that no migraine is caffeine withdrawal headache.

The only known way to distinguish between migraine and a caffeine withdrawal headache that resembles migraine, that is, fulfills International Headache Society diagnostic criteria A, B, C, and D for migraine without aura, is to rule out caffeine use by objective testing.

The IHS diagnostic criteria cannot by decree transform an undemonstrated assumption into a fact. Criterion E in effect defines as separate two conditions never demonstrated to exist separately.

In practice, no physician has ever ruled out caffeine withdrawal headache before diagnosing migraine. Because caffeine withdrawal headache is a possibility in any person using caffeine, the only known way to rule out caffeine withdrawal headache is to rule out caffeine use. Physicians nevertheless routinely diagnose migraine in patients who report using caffeine. Neither can caffeine use be excluded by interviewing the patient, as the reliability of patient reports of caffeine abstinence has not been determined.

Caffeine use is far more prevalent than opioid use: between 87 and 100 percent of the general population uses caffeine,31 so caffeine withdrawal is a possible cause of severe episodic headache in 87 to 100 percent of migraine patients.

There's no demonstrated example of opioid withdrawal headache absent caffeine use. Headache associated with opioid withdrawal may be caffeine withdrawal headache, migraine, or both.

Caffeine is present in plants native to every inhabited continent. It would be difficult to prove any ancient people had no access to caffeine but got migraines anyway. The answer to the question of whether migraine exists absent caffeine or not can best be determined by performing a contemporary trial using living subjects. If today migraine doesn't occur absent caffeine use, we can safely conclude the same was true in ancient times.

Paul suffers a migraine on the road to Damascus around 37 a.d.

In a 1982 nationwide (U.S.) study in which food diaries were kept for children ages five to 18, 98 percent of subjects used caffeine during the seven-day study period.30

You may be mistaken about your absolute lack of caffeine while a child.

Your child may get caffeine from some source you are unaware of.

The mother, in breast milk.

It may be caffeine doesn't always effectively abort caffeine withdrawal headache. We expect administration of an addictive drug to quickly and reliably reverse the withdrawal syndrome of that drug; heroin, for example, quickly and reliably reverses heroin withdrawal. Caffeine may be an exception, however, because of the peculiar mechanism by which caffeine works. Caffeine works by occupying and blockading adenosine receptors. Caffeine cannot, however, remove receptor-bound adenosine, so once adenosine receptors are saturated with adenosine, administered caffeine may not be able to do any good. This may explain why caffeine is most effective when taken early during the migraine episode. It stands to reason that caffeine is 100 percent effective at preventing caffeine withdrawal headache if taken before onset of withdrawal, but it may be caffeine becomes less and less likely to effectively reverse caffeine withdrawal as withdrawal develops. For the same reason, it may be caffeine is 100 percent effective at preventing development of a migraine episode if taken before the migraine episode starts to develop, but becomes less and less likely to be effective as the migraine episode develops.

There is anecdotal evidence of caffeine withdrawal causing visual aura.

In trial studies to date, inducing caffeine withdrawal hasn't induced visual aura, but this may be due to the relative rarity of visual aura. Also: subjects known to have migraine with aura may have been intentionally excluded from participating in trial studies of caffeine withdrawal. Migraine visual aura has never been demonstrated to occur absent caffeine use.

There is no known way to distinguish between a migraine episode triggered by caffeine withdrawal, a migraine episode caused by caffeine withdrawal, and a caffeine withdrawal headache that fulfills the diagnostic criteria for migraine.

Obviously all primary headaches including migraine are secondary to some cause, even if that cause remains unidentified.

The same trial study that would test the theory that caffeine causes some or all migraine would simultaneously test the prevailing assumption that caffeine causes no migraine. Headache researchers have no good excuse for failing to test their basic assumptions about primary headache.

My theory that caffeine causes all primary headache is currently the best available explanation for observations. The burden of falsifying my theory falls to headache researchers, who possess the training and access to funding and facilities needed.