From the article written by Elizabeth Shimer Bowers:

"There's no one pattern. Depression symptoms may gradually progress from the mild, such as choosing to stay home to watch TV instead of going out with friends, to the more severe, such as thoughts of suicide. Or someone may go from seeming perfectly happy to being totally depressed in a matter of days or weeks. The progression varies from person to person."

This article gives 6 depression symptoms you should never ignore.

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