A depressive disorder which often develops during childhood or adolescence, involves less severe symptoms than major depression, but has a longer lasting, more chronic pattern of development, and often results in sufferers being seen as "whiny" or "complaining" would be classified as in the DSM-5_.

dysthymic disorder                        

Explanation:

Dysthymic disorder: In abnormal psychology, the term "dysthymic disorder" is described as one of the mood disorders that is distinguished by an individual having "mild depressive symptoms" that lasts for two years at least.

Symptom: Sadness, fatigue, loss of pleasure in different activities, trouble sleeping, and difficulty concentrating, etc.

In the question above, the given statement represents dysthymic disorder.

nigger, that word was originated for white folks   to keep black people under

and when black people use it, they know that's just how they greet each other

and when white folks use it, they know there's a double meaning under