Regression therapy is becoming recognized as a powerful therapeutic addition to conventional treatments of severe mental traumas, such as phobias, neuroses or psychoses. It was "discovered" by various therapists independently when the therapist would resort to trance or hypnosis in an attempt to cure deeply rooted traumas in his patients.
Once the patient "was under" the therapist would ask him to go back to the time when the trauma in question was inflicted. The therapist would do this assuming that the patient would then "relive" a traumatizing episode of his childhood. But to the great surprise of many therapists, the patient would in some cases start relating episodes that did not belong to this life, but to what looked like a life lived in a different time period. The patient would experience himself wearing different clothes and living in surroundings very different from today. He would then re-experience traumatizing episodes, which he recounted to the therapist. Often this process of recall would be accompanied by strong convulsions of the body and obvious emotional turmoil. After the re-experiencing the patient would come out of the trance feeling exhausted and emotionally spent, but it would then turn out that in the weeks following the session the symptoms would begin to wane. It would often be the case that just a few of these past life sessions would be enough to rid the patient completely of the formerly so life-impeding traumas.
Furthermore it also turned out that many physical symptoms such as pains in the joints and throat, respiratory troubles, stomach pains, sleep problems and asthma could be related to traumas inflicted on the body in former lives and could be cured through regression therapy. In this way regression therapy is an effective tool for curing not only psychic but also physical problems. The effects of regression therapy are well documented throughout the regression therapy literature.
The fact that regression therapy has such convincingly curing effects means that this treatment cannot be "written off" as unscientific, because cure is proof. The convincing results suggest that what the patient "sees" during trance or hypnosis is something factual, a real former life. It cannot just be fantasies or hallucinations, because every therapist knows that these cannot cure deeply rooted traumas. Traumas can only be cured when real past events are analyzed and confronted.
It is often the case that a trauma inflicted during a past life is what led up to the death of the physical body in that particular life. The trauma will often affect the person both physically and mentally in later lives. The following is an example from the regression therapy literature.

A young woman was in treatment for severe headaches. During the course of a past-life regression she went through the major events in a life as an aristocrat during the French Revolution. At the age of sixteen, she was captured by soldiers as she was escaping with her nanny at night. Her parents had already been arrested the day before. She describes the scene at the guillotine:

The very convincing results that are obtained through regression therapy point to the fact that we are dealing with something real, with a real former life of the patient. Because if it is not a former life, what is it? How can we access memories not belonging to our present life whose surfacing can cure us of traumas, if they do not come from a former life? Where else could such memories come from? And why is it that those who work with this kind of therapy and their patients all become convinced that they have lived before?

This is what the well-known Jungian regression therapist Roger Woolger says: "When you have had so many of your own memories of dying, from ugly to mystical, and witnessed hundreds and hundreds do the same, as I have, then post-mortem survival is no longer a mystery, or a postulate, but a living reality".

Books documenting cases and results from regression therapy have been written by: Roger Woolger, Brian L. Weiss, Edith Fiore, Michael Newton, Joel L. Whitton, Winafred Blake Lucas and possibly many more.