From personal experience, memory deficits can arise from depression and from anti-depressant meds.

Depression can seriously interfere with focus and concentration. This can probably have a negative impact on memory. It does for me. I often find myself en route to do something, then arriving and having completely forgotten what I was intending to do. Or maybe it is early Alzheimer's???

Meds, for me, have caused many instances of amnesia. This was obvious in school where I had notes in my own handwriting, even written the same day, where I had not the foggiest recollection of the note's content or even having written it. My MD at that time confirmed the meds can do this.