I've refused to consent to a pdoc contacting a previous pdoc. I didn't agree with his treatment or diagnosis, and did not wish the new pdoc's view of me to be influenced by the old one. The new pdoc was fine with that. Said he liked to come to his own conclusions.

While it would be desirable to me that a new therapist know all about me, I'd prefer that he do that by getting to know me and having me tell him. I'd only want him to contact my old therapist if I trusted my old therapist and agreed with his treatment and diagnosis. And if I trusted my new therapist to disregard any reports from anyone else to come to his own conclusions about me.

I may not be the majority in this. And my view might not be the healthiest one. I wouldn't even want my pdoc and therapist talking to each other. I had a bad experience once, and it made me wary.