What Research Supports the Idea That Physiological Factors May Be

What research supports the idea that physiological factors may be greater contributors to postpartum depression (PPD) than psychological factors?

A) New mothers with low levels of social support are more prone to PPD.
B) Mothers are more likely to experience PPD after the birth of a first child rather than after the birth of a second child.
C) Women across the world experience PDD, even when their support systems and life experiences vary greatly.
D) There is no research to support the idea that physiological factors are greater contributors to PPD.