**My understanding:**

1. **Major Depressive Disorder** is diagnosed in a patient who has at least one depressive episode that has certain characteristics.

2. This episode is called a **major depressive episode**. One of the features such an episode is that it lasts at least **two weeks**.

3. Atypical Depression is a **subtype** of Major Depressive Disorder.

4. Related: [Depression, MDD, Atypical Depression - ELI5](https://www.reddit.com/r/AskDocs/comments/4lwx4w/depression_mdd_atypical_depression_eli5/)

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**Questions:**

1. So is the subdisorder "atypical depression" diagnosed after at least one "atypical depressive **episode**"?

2. So the [symptoms here](https://en.wikipedia.org/wiki/Atypical_depression#Symptoms) then describe **not** the subdisorder "atypical depression" but rather than an "atypical depressive **episode**" of the subdisorder "atypical depression" ?

3. Is an "atypical depressive episode" supposed to last for at least  **two weeks?** Wikipedia (and DSM) says **mood reactivity** is a symptom of "atypical depression" or an "atypical depressive episode". I believe then that if mood reactivity reduces the depression, then the length of the "atypical depressive episode" may vary.

4. **In terms of the episodes, how can atypical depression be a subtype of major depressive disorder?** I thought "atypical depression" or "atypical depressive episodes" has or have mood reactivity, hypersomnia and increased appetite while "major depressive disorder" or "major depressive episodes" has or have insomnia and decreased appetite and doesn't or don't have mood reactivity.

It seems to me that instead atypical depression and major depressive disorder are **types of depressive disorders** rather than atypical depression being a subtype of major depressive disorder, but there aren't depressive disorders [other](https://en.wikipedia.org/wiki/Mood_disorder#Depressive_disorders) than major depressive disorder? That seems kind of strange.