This is an anonymous addition to the post I made about the symptoms of depression:
You hit the nail on the head on every point!
I would add to the social isolation a feeling of guilt. Although depression isn't actually contagious, I often felt like mine was, like if I didn't keep my little black rain clouds home, everyone would feel the weight of them like a wet blanket on a chilly day. I didn't want people to notice because I didn't want to explain but also because I didn't want to burden them. I didn't want them to feel bad for me or feel like they needed to somehow fix what I knew was hopeless, because then they might "catch it" and it would be my fault. I knew that I had wonderful friends and the sisters at church were full of compassion that I was sure should be spent on someone more worthy. That guilt of not wanting to weigh anyone down and fear of burdening others often kept me home and when it didn't, it propelled me into serving others, determined to carry my own weight. While the fear was irrational, serving others actually did help a lot because it helped me focus on others and put my problems in perspective. It also brought me some sense of purpose and accomplishment where I couldn't find them at home. Eventually I realized that if serving others helped me, maybe allowing them to serve me just a little might help them too... Obvious conclusion for most, but my brain was pretty warped for a while.
I'd also add physical symptoms. When I was at my lowest I had headaches, mild but constant body aches, a knot in the stomach and the feeling that life was so heavy it could be felt physically, like my limbs were too weak or tired to get up and accomplish anything. The weight lifted some if I could do simple tasks with someone else. Sometimes there was also a heavy tightness in my chest that felt similar to what I'd imagine a heart attack would feel like, but without the anxiety. Sometimes I felt like my chest was so tight my heart couldn't beat right and my lungs couldn't fill completely. The only way I could get it to relax enough to breath was to cough but I wasn't ever afraid. I actually thought it would be a relief to slip into sudden unconsciousness and never wake up. The idea of verbalizing any of this made the symptoms worse.
Another separate heading would be irritability. This is more often experienced by men, but in the early stages of my depression I experienced it too. Maybe it was because of my inability to concentrate or because I felt totally worthless, but I often felt disproportionately irritated over little things. My kids' noise, typical childhood bickering, my husband's innocent jokes or simple oversights, my own lack of motivation and total disorganization all just annoyed me and I felt snappy and yelled more than my family deserved. Then I'd realize how irrational I was and feel guilty. I realized I couldn't control my lack of patience so I checked out. I'd tell myself that retreating into my Facebook addiction for hours at a time was actually protecting my family from my bad attitude. (I was never actually abusive but I felt as guilty as if I had done much worse than raise my voice in impatience.) It was from that point that I started to feel like they'd be better off without me. I know better now and I'm able to recognize those dangerous thoughts and head them off before they get too out of control, but that's how they started.
My husband was amazingly supportive and understanding and he started to catch on to some of the symptoms when I couldn't communicate them. I never would have gotten through it without him. I can tell it's left a mark on him too though, so for anyone on either end of this relationship, don't forget to take care of yourself too. Don't forget your spouse will need you and you'll need them so recharge when you can.