10453
Caffeine does not appear to be a reinforcing stimulus , and some degree of aversion may actually occur , with people preferring placebo over caffeine in a study on drug abuse liability published in an NIDA research monograph .
 NIDA
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 NIDA