It's the process of identifying it that takes time. If it were sleep apnea, especially severe, a few days to a week of change would be enough to elicit a mental health shift.

The same generalities probably apply to other subtle health issues that can have 2nd order mental health effects.

edit - you're in AB, right next door to me. Go to your GP (and/or find a GP via walk-in by asking for a blood panel / urine test). Have them check for diabetes risks, acth (cortisol) levels re: apnea, and probably a fair few other things that you can at least then check off as invalid.