I just read a study on depression in type 2 diabetics right before starting insulin, and after 6 months on insulin, that reported that insulin (and especially the drop in A1c) lowered rates of depression.
To measure depression, they used the PHQ-9 scale, which I've taken myself at an awful lot of doctor visits. It was developed by Pfizer to help market antidepressants.
Here's how I would have scored the day before I went on insulin:
Q1: Over the last two weeks, how often have you had little interest or pleasure in doing things?
A: Well- I am still interested but it hurts to move, so not much pleasure. Let's say every day (3 points)
Q2: Over the last two weeks, how often have you felt down, depressed, or hopeless?
A: I felt desperate and determined, so I'll say not at all (0 points)
Q3: Over the last two weeks, how often have you had trouble falling asleep, staying asleep, or slept too much?
A: Well gee whiz, I can't sleep when I'm being eaten alive by thirst, and every time I do fall asleep, the need to pee wakes me up. Every single night! (3 points)
Q4: How often have you had trouble with having little to no energy?
A: Every minute of every day (3 points).
Q5: How often have you had an unusually big or little appetite?
A: I'm starving! (3 points)
Q6: Feeling bad about yourself- that you are a failure and have let yourself or others down?
A: Not all of the time, but I feel unable to meet my obligations. Let's say "several days" (1 point)
Q7: Trouble concentrating on things, such as reading the newspaper.
A: I lost the ability to keep concentrating enough to count to 20 roughly three weeks before my diagnosis. (3 points).
Q8: Moving slowly, or the opposite, being fidgety.
A: Well, okay, I'm autistic anyways, so this is one I continue to score positively on. But at the time of diagnosis, it had gotten hard to walk, and people were noticing. 3 points.
Q9: Thoughts of hurting and/or killing yourself.
A: Actually, for the first time in many years, I STOPPED having these thoughts shortly before I was diagnosed. 0 points.
Bonus Question: How difficult have these things made it for you to do your work and get along with people?
A: Really difficult.
According to the study I just read on type 2 diabetes, a score of 15-19 qualified as moderately severe (20 was severe depression).
And yet, I was not depressed, just in DKA.
The article said every 1 point drop in A1c lowered score by an average of 40%. I say yeah, that's cause the high A1cs mess with memory, energy, sleep, and hunger, not because they cause depression. It's not pathological to feel exhausted and hungry if you're high.