 As the understanding of the workings of the subconscious continues to evolve, the application of the therapy continues to change.The three most influential changes have been in Specific Questioning (1992) to gain more accurate subconscious information; a subconscious cause/effect mapping system (SRBC)(1996) to streamline the process of curative hypnotherapy treatment; and the 'LBR Criteria' (2003) to be able to differentiate more easily between causal and trigger events and helping to target more accurately the erroneous data which requires reinterpretation.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.