Lyric discussion by pickefoo 

Cover art for Black Dog on My Shoulder lyrics by Manic Street Preachers

This song is about depression, nothing more and nothing less. There are several references that point this out.

"Black Dog on my shoulder", yes. Winston Churchill referred to depression being the black dog on his shoulder, and this has to many become a way of referring to the illness.

"My mouth is so dry" Dryness of the mouth is a common symptom associated with the use of SSRI and other anti-depressant mediciation.

"Double vision the way it is", again, another common symptom of this medication.

My Interpretation