1854
A complete understanding of depression during the postpartum period has yet to be established , although disruptions in the hypothalamic - pituitary - adrenal axis and stress during the postpartum may be involved .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None