File size of PSD files has ballooned

I am using Photoshop (automatic updates, currently on 24.6.0) on macOS (Ventura, latest version) and have noticed in the past few weeks the size of PSD files has increased considerably.

I have a file I am working on now which is over 800mb, whereas a file with the same dimensions and has the same number of layers, etc. from last year is 42mb.

I don't think I have made any changes to File Handling or the compression settings.

Can anyone please advise? 800mb per file is untenable!