Coherence therapy was developed in the late 1980s and early 1990s as Ecker and Hulley investigated why certain psychotherapy sessions seemed to produce deep transformations of emotional meaning and immediate symptom cessation, while most sessions did not. Studying many such transformative sessions for several years, they concluded that in these sessions, the therapist had desisted from doing anything to oppose or counteract the symptom, and the client had a powerful, felt experience of some previously unrecognized "emotional truth" that was making the symptom necessary to have.