C. It is difficult to seek treatment for depression, as it is viewed as a glorified form of sadness rather than a serious mental illness.
Explanation:
In his speech, Andrew Solomon narrated his ordeal with depression. This disease is one suffered by many who do not really recognize its difference with sadness. They see depression as a mood which is normal for all humans, and so they do not believe that it requires treatments. They believe that it is something that can be adapted to.
Andrew Solomon sees it differently. He compared sadness to an iron with little rust which can be overcome by just painting and polishing while he compared depression to an iron which has rusted by over a hundred years and has turned to "a pile of orange dust". So, depression is a serious medical condition that needs urgent attention.
