There have always been those who think Churchill's recurring melancholy could have been a symptom of mental illness.

BBC: A Point of View: Churchill, chance and the 'black dog'

Disapproval, reticence and treating suicide solely as a symptom of mental illness have not actually done much to curb it.

ECONOMIST: Let death be my dominion

To be diagnosed with conversion disorder, you must meet the symptom criteria spelled out in the Diagnostic and Statistical Manual of Mental Disorders (DSM).

CNN: Conversion disorder

To be diagnosed with atypical depression, you must meet the symptom criteria spelled out in the Diagnostic and Statistical Manual of Mental Disorders (DSM), published by the American Psychiatric Association.

CNN: Atypical depression

In one study, funded by the National Institute of Mental Health, only one-third of patients achieved remission of depressive symptoms, defined as becoming symptom-free.

CNN: Using downward dogs to treat depression