Major Depressive Episode[1] - At least 5 of the following symptoms, one of which must be depressed mood or loss of interest/pleasure, in the same 2 week period:
Insomnia
Hypersomnia
Depressed mood
Loss of interest or pleasure
Feelings of worthlessness
Fatigue
Diminished ability to think or make decisions
Increased/decreased appetite
Psychomotor retardation or agitation
Hopelessness
Suicidal thoughts
Other symptoms: diminished sex drive, avoidance of other people, overwhelming feelings of sadness or grief
Manic Episode[1] - A period of abnormally elevated, expansive, or irritable mood, lasting at least 1 week.
Mixed episode[1] - Contains features of a major depressive episode and a manic episode nearly every day for 1 week.
Hypomanic episode[1] - A period of abnormally elevated, expansive, or irritable mood, lasting 4 days, no impairment in social or occupational functioning.
Major Depressive Disorder[1] - 2 or more major depressive episodes, absence of manic, hypomanic, or mixed episode
Test yourself on these definitions.

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1. Toronto Notes 2004: Review for the MCCQE. Eds: A. Molckovsky and KS Pirzada. Toronto Notes Publishing 2004, Toronto.