When is a disease not a disease? Among the Miskito People of eastern Central America, the condition known as "Grisi Siknis" has afflicted dozens, spreading like an epidemic through the population - especially the young. But no medical cause can be established, and no medical treatment has been demonstrated to work reliably. Indeed, the only people who can successfully treat the disease are Miskito herbalists and witch-doctors. The disease shares many common features with a number of mysterious conditions affecting people in the developed world: are these examples of a class of disease that only alternative medicine can cure?

The condition spreads like the flu, but seems to target a specific demographic - teenagers, usually girls and usually between the ages of 15 and 18. The patients go into a manic frenzy, feelings of anger, fear or anxiety giving way to a loss of control. Often the victim becomes violent, and almost "superhuman", performing feats of strength or ignoring bodily injuries. A common feature is a feeling of threat - the victims feel as if they are under attack from some unknown spirits. Grisi siknis translates as "crazy sickness", and that neatly sums up the condition - the patient goes crazy.

Professor Pablo McDavis, a researcher into the disease based in the area, was quoted recently as being perplexed:

"We have taken samples of blood from patients while suffering an attack and, in a lab, we can't detect anything.

"Drugs or injections tend to only increase a patient's aggressiveness. Clinically we can't detect anything.

"It is like an outbreak. If an attack is not contained quickly, it can spread throughout an entire community."

Belief in spirits, curses and black magic is very strong among the Miskito population, and those afflicted turn to local healers and witch doctors. These people claim that the condition is treatable - a potion either consumed or bathed in can apparently cure the disease in the space of a few days. Many in the community believe that the healers are lifting a curse from the victims.

It's tempting to take a sort of patronising view of this tribe and their mystery illness, but actually we've got no right to be smug, because a whole litany of similar conditions affect cultures all over the world including our own. These conditions are collectively termed "culture bound syndromes", and what marks them out as unusual is that while the victims appear to be displaying genuine psychological and physical problems, the syndrome is only recognised within a specific culture (while being completely unheard of in others), and none of the symptoms can be detected by medical tests or observations.

Examples include the infamous "penis panics" in West Africa, in which sufferers believe that some person or spirit has stolen their favourite appendage; Morgellons in the United States (although it could almost be described as an Internet disease), which is most likely simply delusional parasitosis; Fan Death in South Korea, in which people believe that electric fans left on overnight can cause death by suffocation, poisoning, or hypothermia, through some unknown mechanism; Arctic hysteria in Eskimos (although this could conceivably be due to Vitamin A poisoning); and many other fascinating examples - enough to fill many more blog posts.

Science-based medicine relies on the tangible - no amount of samples and measurements can help you when there is nothing to measure. Clinical trials would probably conclude that the potions of the witchdoctors' potions worked, but they may not shed much light on the mechanisms involved. Instead, culturally-bound syndromes have been classified as psychiatric conditions. The American Psychiatric Association say [2]:

"The term culture-bound syndrome denotes recurrent, locality-specific patterns of aberrant behavior and troubling experience that may or may not be linked to a particular DSM-IV diagnostic category. Many of these patterns are indigenously considered to be 'illnesses,' or at least afflictions, and most have local names. Althought presentations conforming to the major DSM-IV categories can be found throughout the world, the particular symptoms, course, and social response are very often influenced by local cultural factors. In contrast, culture-bound syndromes are generally limited to specific societies or culture areas and are localized, folk, diagnostic categories that frame coherent meanings for certain repetitive, patterned, and troubling sets of experiences and observations."

The fundamental problem for Doctors using the principles of evidence-based medicine is that this is not an evidence-based disease. It exists only within the context of the patients personal and cultural understanding of the body and disease. This means that the doctor has to be able to do one of three things, which are in turn ignorant, unethical, or likely to be ineffective.

The first is for the doctor to genuinely share the beliefs of the patient, and offer the appropriate folk medicine treatment. Clearly this is pretty much a non-starter for modern doctors.

The second approach is to try to educate the patient to see the condition the way that the doctor sees it. The problem with this is that at best it's unlikely to work - one doctor's opinion is unlikely to overturn decades of cultural learning - and at worst it can be downright offensive to sufferers. Many people who believe they have Morgellons for example are told by their doctors that they have "delusional parasitosis", but this isn't a very nice diagnosis to hear - nobody wants to have it suggested to them that they're delusional. As a result, patients may refuse the appropriate treatments, creating a serious dilemma for the doctor.

The third approach is for the doctor to pretend to share the patient's understanding of the disease, and to then offer either the folk medicine treatment or a medical alternative: "oh yes, aspirin are very good for dispelling evil spirits." The problem with this approach is that it's regarded as deeply unethical - the doctor-patient relationship is supposed to be built on trust, and for a doctor to deliberately lie to a patient about their illness or treatment is abhorrent in the eyes of many (and let's not ignore the possibility of getting sued at some later stage).

Which brings us all the way across to the issue of the placebo effect in modern medicine. Many common complaints have a strong psychological component - back pain for example - and in these cases quack medicine and the placebo effect can be a great help. Again though doctors run into thorny ethical dilemmas - placebos work best when given by deception, and deception runs against medical ethics. It's a debate that I suspect will rumble on for years. Ben Goldacre neatly summed-up the dilemma in a column last year:

"Sugar pills are the future, if only there was a way to give them with integrity, and a straight face."

It's a dilemma of course that doesn't affect the US$60bn alternative medicine industry, and indeed it's in scenarios like this that quackery survives and thrives. Alternative medicine practitioners don't have to demonstrate that they're product works, or provide evidence of efficacy or even biological explanations. Freed from ethical and scientific obligations they can more directly connect with the patient's own ideology to provide the desired treatment. The question is, how far down that road should conventional medicine go?

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[1] Dennis, Phil (1981). Grisi Siknis Among the Miskito. Medical Anthropology 5(4): 445-505.

[2] American Psychiatric Association (2000). Diagnostic and Statistical Manual of Mental Disorders, 4th ed., text revision. American Psychiatric Pub. p. 898. ISBN 9780890420256.