Equus (1977), directed by Sidney Lumet.
Fairly heavy film about psycho-sexual-religious derangement. Good cast, with Richard Burton as the troubled shrink, talking to the camera. He realizes that psychiatry is not enough, but doesn't know what else to do.
I have not read or seen the play so can't comment on the adaptation. Gruesome, hard to watch climax of horse mutilation, not real but still wrenching.
Everyone in psychiatry-themed movies seems to be cracking up to some degree.
Some nudity. I would particularly like to thank Jenny Agutter for her efforts in this direction.
The DVD is 4:3 letterboxed.