in contrast with only 4% (239/4789) among control group. So self-disclosure of age is more prevalent among vulnerable users. Figure \[age\_dist\] depicts the age distribution in $U_a$. The general trend, consistent with the results in [@zhang2016your; @liao2014study], is biased toward young people. Indeed, according to Pew, 47% of Twitter users are younger than 30 years old [@duggan2015demographics]. Similar data collection procedure with comparable distribution have been used in many prior efforts [@al2012homophily; @liao2014study; @zhang2016your]. We discuss our approach to mitigate the impact of the bias in Section 4.1. The median age is 17 for depressed class versus 19 for control class suggesting either likely depressed-user population is younger, or depressed youngsters are more likely to disclose their age for connecting to their peers (social homophily.) [@al2012homophily]

![The age distribution for depressed and control users in ground-truth dataset](agedist){width="35.00000%"}

\[age\_dist\]

**Gender Enabled Ground-truth Dataset:** We selected a subset of 1464 users $U_g$ from $U_t$ who disclose their gender in their profile description. From 1464 users 64% belonged to the depressed group, and the rest (36%) to the control group. 23% of the likely depressed users disclose their gender which is considerably higher (12%) than that for the control class. Once again, gender 