Is it possible to heal (by mind, not by medical treatment) diseases that lead to unrecoverable physical damage to the body/ parts of it, such as Alzheimer's disease?
Edit: that was probably a bad example as a person with Alzheimer would probably have hard time doing mental healing... but I hope you know what I mean :-)
Energy healing is possible. I don't know that you would be able to cure a diseases but most people use it to comfort another. Also it would be ignorant to use only energy healing. It is best to seek medical help and use energy healing as an adjunct.