The percent of kids helped depends on the disease:
- Cystic fibrosis 86% report it helpful
- Vocal cord dysfunction 54% resolved and another 38% resolved
- Getting to sleep improved in 90%
One caveat about those numbers. The kids tested were chosen "because it was felt that there was a significant psychological component in their presentation."
I don't find this woo-woo at all. If playing with kids heads (or rather teaching them to do it themselves) can reduce their symptoms by controlling their response to discomfort, more power to them. It doesn't cure the disease, but ameliorating the symptoms is cool enough for now.