I tried vicodin for fibromyalgia and though it did not relieve the muscle/bone pain it certainly lifted my mood! I was tempted to continue taking it just as a mood-lifter! Yes, it's in the class of 'opiates' and can be addictive. I had success using 5-htp and b-complex and a good multi. After a few weeks of those I felt an improved difference in my mood and lost interest in using vicodin as a mood-lifter.
So yes I hear where people are coming from when they talk of using opiates as an anti-depressant. The feeling is grand! Discuss with your doctor.