I'm all too familiar with Vicodin for the same reason, a history of major spinal surgery (cervical), and I've noticed the same thing with regard to Vicodin and depression. Even previous to my spinal ailments I nearly always suffered from migraines though, since I was a small child, and what the relief I finally felt with Vicodin (albeit temporary as you say) caused me to consider is the amount to which physical pain has factored into my lifelong battle with depression. When I experienced actually being out of pain, I couldn't remember ever having felt it free of it before, or at the very least since the time I started having migraines there was never a moment that I wasn't either in pain, or worrying that I was about to be, with recurrent migraines leaving a host of creeping symptoms in their stead. I realized that I can't even imagine what life would have been like without any kind of chronic pain, but that it would have been very different indeed; freeing. And yet, with nothing to be freed from.. just simply free, in a way I can't comprehend. What vision would be to someone who has always been blind.

I don't know; in fact there's just no way for me to imagine what it would have been like. For me, I have only ever felt it in occasional medically induced increments such as you've described.

But it seems to me that the weight on my psyche represented by my constant struggle with pain has been far more significant than I ever had an opportunity to consider through comparison. When I was growing up, I wasn't allowed to express distress about pain I was in; I had to "suck it up" and "stop complaining", and "not be such a crybaby". And so I did. I was trained out of expressing anything, about any pain I experienced. Which seemed great to everybody, including myself at the time. I took on an appearance of being very strong, a real scrapper, picking myself up by my bootstraps, and so on. Except that I buried so many elements of my reality into my tiny little 5-year old psyche, perhaps even including the ability to identify and process my own pain.

But I digress.

Of course, without any natural experience of real absence of pain to compare it to, it's rather hard for me to say how much any opiate-induced psychological relief I've experienced has really been my own, and how much of it has been part and parcel of the drug's effects itself. Some lovely combination thereof, I suppose; for a couple of hours anyway.