depression is mainly low serotonin. which by itself is ok as long as you dont need the perks of high serotonin to survive. like having to hold down a high caliber job or something. but if serotonin gets too low it can be painful.
the inability to feel pleasure is more if your dopamine is low and stuck. because if its just low you can use things like food, orgasm, showers, etc... to raise it. but if it gets stuck low then none of those things will work and then the mind panics and may become suicidal. especially if its happening at the same time the serotonin is down, or too low.
if the serotonin and dopamine are both really low then it can be unbearable. a person might desperately want to escape and be too scared to go to a hospital for fear they would lock them ina padded room and force them to endure that pain with no way of escaping.
When even your loved ones stop mattering and feel more like a chore. I have become distant and indifferent during these times and that has hurt them. I would say that is what bothers me the most.
"Brain fog" might best describe the worst aspect of it for me. I've noticed some things that would usually be interesting to me, are less so, because the thinking is corrupted by this cloud. Makes it harder to concentrate, less focus and poorer attention span. Lack of clarity. Some exercise and eating decent foods helps but it is still there often enough.
If I had to pick one it would be the inability to find joy in the hobbies that interest me or even feeling indifferent toward my loved ones. Numbness is an awful feeling because emotions are so very important in this world. Emotions=Living. I hated feeling no sense of happiness that I would go spend crazy just to get a temporary feeling of happiness that buying something causes. I can compare being numb to being a zombie. Thankfully, it can be managed for the most part by taking the right medicine combo.