Tracing the evolution of Hypnotherapy :

Franz Anton Mesmer (1734 – 1815), was a German physician and astrologist, who invented what he called magnétisme animal (animal magnetism) and other spiritual forces often grouped together as mesmerism. Mesmer applied magnets to his patients’ bodies and produced remarkable results, especially in the case of a young woman suffering from hysteria.

In some ways the beliefs and practices of Mesmer look back to an earlier period of magical medicine as far back as two hundred years before his own time to the era of Paracelsus.

Dr James Braid (1796 - 1860) is regarded by many as the 'Father of Hypnosis' for he was the man who coined the term "hypnosis".

James Baird began his own experiments in an attempt to find a scientific reason for the trance. He quickly dismissed the erroneous theories of the time that Mesmeric trances were due to some form of magnetism.
By 1847 he discovered that all the major phenomena of hypnotism such as catalepsy, anesthesia and amnesia, could be induced without sleep.

Dr. Sigmund Freud (1856 – 1939) was a Jewish - Austrian neurologist who founded the psychoanalytic school of psychiatry.

Freud is best known for his theories of the unconscious mind and the defense mechanism of repression, and for creating the clinical practice of psychoanalysis for treating psychopathology through dialogue between a patient, technically referred to as an "analysand", and a psychoanalyst.

Dr. Brian Weiss of US extensively worked on this during 1980s & can be   rightly be called as the person, who brought this science to the centre – stage. He was M. D. & Chief of Psychiatry at University–affiliated hospital in Miami, Florida

He is a very renowned Psychiatrist of US and the only person in the World, today, who knows the maximum about both these sciences.

Dr. Brian Weiss
His background : 

Initially he was very skeptic about this science but after 2 decades of research he is one of its greatest advocates. He has delivered concrete & amazing results that have been accepted by the Medical fraternity, the World over.

He had received his MD in Psychiatry from Yale School of Medicine. As Head of Psychopharmacology Division at the University of Miami, he had received national recognition in the fields of biological psychiatry & substance abuse. Within the next 4 years he became the chief of Psychiatry of a very large Hospital in Miami, Florida in US. By then he had published 37 scientific papers in the leading US Medical Journals.

 (Quote from his book – Many Lives Many Masters).

“Years of disciplined study had trained my mind to think as a Scientist & a Physician, molding me along the narrow paths of conservatism in my profession. I distrusted anything that could not me proved by traditional scientific methods. I was aware of some of the studies in Parapsychology (including Hypnotherapy) being conducted at major Universities across the country, but they did not hold my attention. It all seemed too farfetched to me.

Then I met Catherine. For 18 months I used conventional methods of (Psychiatric) therapy to help her overcome her symptoms. When nothing seemed to work, I tried Hypnosis. I was absolutely amazed with the events that unfolded. Nothing in my background had prepared me for this.

I do not have a scientific explanation for what happened. There is far too much about the human mind that is beyond our comprehension. Perhaps under Hypnosis Catherine was able to focus in, on the part of her sub conscious mind that stored the events of her life or perhaps she had tapped into, what the Psychoanalyst Carl Jung termed as the “the collective unconscious”, the energy source that surrounds us & contains the memories of the entire human race.

Throughout history humankind has been resistant to change & to the acceptance of new ideas. Historical lore is replete with examples. When Galileo discovered the moons of Jupiter the astronomers of that time refused to accept or even to look at the satellites because the existence of these moons conflicted with their accepted beliefs. So it is now with Psychiatrists & other therapists who refuse to examine and evaluate the considerable evidence that is being gathered about this remarkable science.