Placebo, or what's likely happening is that Reiki recipients are experiencing the relaxation response as a part of the session.
(See the Benson-Henry Institute for Mind Body Medicine website. Benson is someone who has been studying the relaxation response -- as a completely physical, ordinary phenomenon that can be induced by "spiritual" practices.)
Mind you, what a Reiki practitioner believes he/she is doing is probably not causing the parasymthetic nervous system response, but the many factors of a (typical) session probably are causing it:
* the recipient is invited to lay down on a massage table
* soft music is played
* lights are dimmed
* the recipient is encouraged to breathe deeply and steadily, and clear the mind
* warm hards are placed on different parts of the body
* the practitioner speaks to the recipient in a soothing voice
...All these things, completely ordinary, can add up to a genuine, physical relaxation response that relaxes muscles, lowers blood pressure, and maybe even is accompanied by a release of endorpins.
Again, does that mean the Reiki practitioner is causing it? No, it just means they're assisting in creating it by providing a calm environment and some pacifying sensory stimulation.
Well, no.... the combination of things you mentioned means that the therapist IS causing it. Not merely "assisting". Mind you, they're not doing it through any amazing channeling of chi or other energy points, just physical and physiological means that are clearly able to be understood, as you show.
My significant other is a Thai Massage Therapist. We don't do "licenses" over here, but she's got all the certificates from the best schools in Thailand. And the courses were not Reiki-ish
"two session six hour you give me three hundred dollah". They were 2/4/6 weeks, 5-8 hours a day depending on what module she was taking. I think the total time in the classes including hands-on training/practice was at least 150/200 hours. And I think the total cost of all of it was something around USD 3000.
And she doesn't claim to cure things through chi. She knows how to relax people who've got minor/major aches and pains from exercise or stress, and if any of you know Asians, you'll know that many of the cultures over here get massages as a matter of course in their week. It's pretty standard over here, and most people I know wouldn't bother with reiki. I've seen a couple of promos posing as newscasts on reiki, and I was rather surprised that the therapists were gwei lohs.
By the way, Supamart's not practicing... she's busy being a mommy, but she does do some work on friends. Her aunt called her with what sounded like something more internal (e.g. not muscular), and she sent her to a doctor. She's a buddhist and burns incense and goest to temples and such, but she's not irresponsible. They clearly taught her this in the classes she took, because going in, she really believed she was going to learn to be Miracle Max, I think. On the whole of it, she came out of it clearer thinking than when she went in.
ETA: Bumlet - if your friend can handle it JUST as massage therapy and none of the esoteric woo, well... okay. But I'd keep a skeptical eye on her. They tend to slip. If she's into the spirituality crud already (which I fear as you've already said that she's into various sorts of woo), then I'm afraid it's time to step up to the line. I don't interefere with Supamart's Buddhism or other beliefs (the girl's never met a temple she didn't like) like dragons or ghosts, because they're just cultural and rather harmless. But I'd never let her woo effect our son's health or my/her health. And I like to think that if she was going to potentially offer her services and possibly harm someone else, that I'd be able to screw up the courage to talk her out of it.