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In page Hypnotherapy:

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Hypnotherapy expert Dr Peter Marshall, former Principal of the London School of Hypnotherapy and Psychotherapy Ltd. and author of A Handbook of Hypnotherapy, devised the Trance Theory of Mental Illness, which provides that people suffering from depression, or certain other kinds of neuroses, are already living in a trance and so the hypnotherapist does not need to induce them, but rather to make them understand this and help lead them out of it.[4][5]