22642
A large amount of the data gathered in the last 50 years support the hypothesis that alterations of the serotonin ( 5 - HT ) neurotransmission play a crucial role in the pathophysiology of not only major depression ( MD ) , but also of different neuropsychiatric disorders .
 serotonin, 5 - HT
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 serotonin, 5 - HT