97612
Participation in this study became unrealistic , as patients did not want to participate in treatment of total darkness from 6 p.m. to 8 a.m. More recently , with the discovery of intrinsically photosensitive retinal ganglion cells , it has been hypothesized that similar results could be achieved by blocking blue light , as a potential treatment for bipolar disorder .
 bipolar disorder
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 bipolar disorder