There's a book on that very subject:
Contemporary Psychoanalytic Musings: Review of "Gaslighting, the Double Whammy, Interrogation, and other Methods of Covert Control in Psychotherapy and Analysis" by Theo Dorpat (1996).

My relationship devolved into gaslighting. My co-therapists were scornful, ridiculing and bullying trying to keep me as a client. Yet when I raised the issue, they blamed my "distortion," promising the conflict signaled I was on the verge of a real breakthrough. They were so brainwashed by their own theories they couldn't be responsible for their abuse.