'Look into their eyes' - Should we be diagnosing depression in the office?

In the early(ish) days of my career, work would normally be done by 9pm or 10pm. As I waved goodbye to the other bodies still at desks on the agency floor, a Coolio lyric from 90s hit Gangsta’s Paradise would often pop into my head: “as I walk through the valley in the shadow of death.” 
Not because the song is catchy as hell but amongst the red eyes, shaking hands, tired limbs,