Hollywood Will Contain Your Madness
When your main character is an amnesiac with massive psychological trauma, you'd think you'd throw something warped in your narrative technique. Maybe put some wavery fish-eye lens in there; maybe break up the flow of time so you're not sure whether you're in a flashback or in the present. You've got a story about madness; go a little mad, Hitchcock, baby.
Hitchcock baby doesn't go mad though. Instead, Spellbound is all about taking mental illness and putting it into the box labeled "standard Hollywood movie." The film is almost entirely from Constance's perspective… which is to say it's from the point of view of the analyst, not the patient.
Ballantyne has some psychological episodes—he passes out several times, for example. And there is the weird scene where he wanders around with a straight razor and looks through the bottom of a milk glass. But in general you always see those happen through Constance's eyes: she watches him faint, so you don't get to see what Ballantyne himself is experiencing as he does it.
Similarly, Ballantyne's weird, disturbing, Dali-like dream is narrated by Ballantyne to the analysts. Brulov even reassures him about it:
BRULOV: This is just plain, ordinary, wishful dreaming.
The surreal scenery and disturbing imagery is all carefully placed in a normal, calm narrative. You know what's real and what isn't; you're reassured that the abnormal and unusual is in fact explicable and totally not at all bizarre. Just ignore those giant scissors, folks.
Spellbound uses its narrative technique to contain mental illness and madness. The analyst controls the madness, and everything is in its place. In later films, Hitchcock would use narrative techniques to shake you up… but here, he's using them to make sure you know everything is in its place, from the straight razor to the kissing bug.