Several Nurses Are Discussing Whether or Not There Is a Single

Several nurses are discussing whether or not there is a single universally accepted hypothesis that provides an explanation about the pathophysiology and etiology of depression. Which statement by the nurse is accurate?

A) "Cerebral structure is responsible for depression."
B) "We know that heredity is the single cause of depression."
C) "Because all patients respond the same to SSRIs, we have a thorough understanding of the neurochemistry of depression."
D) "There is no unified hypothesis regarding pathophysiology and etiology of depression, in part because patients demonstrate individualized responses to treatments."