Does Reddit attract a disproportionate number of users with mental health issues?

I'm mostly active on r/askreddit and r/relationship_advice, so I'm admittedly seeing only a slice of Reddit, however the percentage of posts stating the author has severe depression, anxiety, and other mental health issues is astounding.

There's an occasional question on r/askreddit along the lines of "How are you doing?" and the responses are overwhelmingly negative with many, many people claiming to suffer from some form of mental illness. A very high percentage of r/relationship_advice posts are from people either dealing with there own mental health issues or struggling in a relationship with someone who has mental health issues.

What gives? I don't notice this trend in other social media outlets. Is there something about Reddit that attracts such a demographic?