The name of the character Tod Browning is an homage to the director of such horror films as Dracula (1931).
Director Seth Holt died from a heart attack before completing this film. It was finished by Hammer Studios head Michael Carreras.
The UK cinema version was cut by the BBFC to remove a shot of George Coulouris being struck across the face by male nurse James Cossins as there was public concern about the treatment of mental patients at the time.