In its severe forms, depression paralyzes

all of the otherwise vital forces that make us human, leaving instead a bleak, despairing, desperate, and deadened state. . . Life is bloodless, pulseless, and yet present enough to allow a suffocating horror and pain. All bearings are lost; all things are dark and drained of feeling. The slippage into futility is first gradual, then utter. Thought, which is as pervasively affected by depression as mood, is morbid, confused, and stuporous. It is also vacillating, ruminative, indecisive, and self-castigating. The body is bone-weary; there is no will; nothing is that is not an effort, and nothing at all seems worth it. Sleep is fragmented, elusive, or all-consuming. Like an unstable, gas, an irritable exhaustion seeps into every crevice of thought and action.”
― Kay Redfield Jamison