The placebo effect is well documented - what isn't well documented is it's opposite - the nocebo effect - just as one can convince their body they are well, they can do the opposite and actually kill - it's most well known documentation lies in those who believe in voodoo and believe they will die once cursed, and indeed, perfectly healthy people have died.
I think rather than placebo effect having any real impact on CHers, it's opposite, nocebo effect, can have drastic and damaging impact. That's where I personally see tools like the secret and story principle helping.
CH is a rather tricky disorder, it can be confused with a multitude of other ICHD diagnoses, and when an underlying condition is 'cured' the clusters will go away as well.
Regardless, debating the validity of such things is subjective and truly pointless when it comes to CH. For every 'cured' sufferer, there are many things that one can say contributed.
Another similar tool one can use is Change Your Story Change Your Life - which can be found in it's full book pdf format, free, at storyhealer.com (story principle mentioned above)
I won't say these tools do work or don't work, what I *will* say is that all the tools you can find will help you *manage* your CH and your life.
I've had more than one person tell me that the nutritional supplements I currently use have cured their clusters, and in almost every case, a) they didn't have clusters, and b) they likely went into a lengthy remission because of the vitamin D3, B2, B6, B12, Taurine, Omega 3 etc. that is in the product.
Those are things that are well documented, so it stands to reason that one MIGHT see significant benefit from the product.
The brain is a powerful organ, and it has abilities to do things we haven't even begun to understand yet - we hardly know that much about CH to begin with - it's only recently been documented through case studies that CH is not only a primary headache disorder, but also a secondary disorder, 2 disorders at least that I know of - Moya Moya (and that is only anecdotal

Deej), and pituitary disorders.
So it's clear we simply don't have enough knowledge to unequivocally state something is or is not a cure at this stage in the process.
Just my 2 cents, and bunch of hot air worth

Cat