Table 1.

List of all sources used with their number of posts, date range of posts, and the available demographic attributes.

Source	Number of posts	Date range	Gender	Age	Ethnicity	Location
TwitterHealth [24]	11,637,888	May 2, 2013 to November 11, 2013	Gender classifier [17]	Noa	Ethnicity classifier [17]	Yesb
Google+Health [25]	186,666	August 24, 2009 to January 5, 2014	Yes	Yes	Ethnicity classifier [17]	Yes
DailyStrength [26]	1,319,622	June 21, 2006 to December 3, 2017	Yes	Yes	No	Yes
WebMD [27]	318,297	December 24, 2006 to May 11, 2019	Gender classifier [12]	No	No	No

^aThe demographic attribute is not provided by the source and no classifier is used because of low accuracy.

^bThe demographic attribute is provided by the source.