I remember one late winter day in Lincoln, Nebraska. There was a blue sky, a cold wind, and bits of snow drifts that had not yet melted. I was walking towards a classroom and my friend Lee was leaving the building. She asked how I was doing.
"Fine," I said. "Well, I'm feeling depressed but everything is going well in my life so objectively I guess I am doing fine." This was the first time I remember actually being able to observe my feeling of being depressed as being separate from what was going on outside of myself. Years later when I began to study cognitive therapy that conversation came back to me. Cognitive therapy examines how thought affects life. Here is the analogy I use now: My favorite place in the world is a small sea town in Oregon. It sits atop a huge basalt flow that dates back to a time when the whole west coast was 100 feet below the ocean surface. There is no sandy beach here, merely a sharp drop from the edge of the rock to the ocean.
When a log comes rolling in on the tide, you can stand above it and watch it get smashed into the rock and then drift back out, only to come in again and crash against the stone with each succeeding wave. With depression you get a choice: you can be on the log or you can be on the stone above the log watching. You can be in the middle of the devastating, soul eating thoughts and beliefs that go with depression or you can stand back and observe your thoughts as something that is created in your brain but that is not very accurate.
The negative thinking in depression appears to be related to low levels of certain neurotransmitters in the brain. When these neurotransmitters drop below a certain level, negative thoughts come unbidden into the mind. Interestingly enough, it appears that having negative thoughts can also cause the neurotransmitters to drop. This becomes a feedback loop, one causing the other, causing the other. Sometimes a person can actually feel themselves spiraling into depression. Something bad happens, they start ruminating about this and that leads to more negative thoughts that generalize to other aspects of life.