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Does depression have common stages, which are recognizable through majority of patients? If so what would these be?

Hello, people of AskScience.

This question was on my mind and you find a lot blog/articles about this, but I wanted someone with scientific background to give me an answer.

Thank you either way.
gpt
Hi there!

Mental illnesses are of course hard to define and categorize, but depression actually received a lot of attention. 
the DSM (Diagnostic and statistical manual of mental disorders) gives standard criteria to diagnose and classify mental illnesses. To diagnose a depression (and there are different types of it) you need to make sure the patient has a required number of symptoms. For example, in order to be diagnosed with a Major Depression state a patient needs to have 5 out of ~9 given symptoms, for at least 2 weeks, linked to a change in the patient's functioning compared with before the symptoms. At least 2 of these symptoms have to be "depressive mood" or " lost of interest / pleasure in things". And then, you also have several types of Major depression states, with several degrees of severity (low, average, severe without psychotic caracteristics, severe with psychotic caracteristics). The depression can also be described by its state: in a period of complete or partial remission for example.
As you can see, there are common traits in people with depression, although they don't all have every symptoms, and there are a lot of subtypes. 
Someone can have some of the symptoms but not be in a depressive state. 

There are some evidences that depression is better described as a continuum (like a gradation) than as a categoric illness (categoric = present vs absent) (Ruscio & Ruscio, 2000; Ruscio & Ruscio, 2002; Hankin & al. 2005).

Is it what you wanted to know?