depression

I used to suffer from depression, but now I'm mostly content with my life.

[…] your illness reflects the textbook description of bipolar disorder (euphoric, grandiose, manic highs followed by deep depressions,[…]

It was not far from the house; but the ground sank into a depression there, and the ridge of it behind shut out everything except just the roof of the tallest hayrick. As one sat on the sward behind the elm, with the back turned on the rick and nothing in front but the tall elms and the oaks in the other hedge, it was quite easy to fancy it the verge of the prairie with the backwoods close by.

The Great Depression was the worst financial event in US history.

Depression of the lever starts the machine.