The german ethnopharmacologist Dr. Christian Rätsch (RIP) has speculated that opioid addiction is the brains reaction to a natural deficit of endorphins in the body of the addict. The compulsive desire to take opioids is therefore an attempt to increase endorphin release in the body. If that hypothesis is correct, then addiction is indeed not a brain disease as it is popularily believed today, but a natural impulse of the body to get rid of the lack of a certain neurochemical. Since I have absolutely no expertise on this subject I cannot judge if it is valid, but it makes sense to me.
In my humble opinion, that doesn't make sense. A good dose of an opiate (in an individual with low-moderate tolerance) provide certain mind alteration, such as the production of euphoria, and a certain pleasure relaxation that most humans in sober consciousness can not recreate by their own.
Any human with just a totally fine endorphin system will not enjoy themselves just looking at a fucking wall for 30 minutes (or if you don't want to go that hardcore, just maybe walking people going by in the city while you are sitting on a bench).
When you are doing opiates you basically are buying high pleasurable effects that otherwise in the sober-survival designed state of consciousness that humans are, would entail either sex, achieving a big goal, and incredible massage, running a 50km marathon, ...etc.
If I have gotten something of utility of getting high on opioids is that when I´m high and I look at peoples faces and behaviour. All those 'normal people' with healthy endorphin systems are really fucking stressed all the time and do not know how to enjoy themselves looking at a tree and orgasming themselves with the breeze of the air, instead they constantly are running around to get 'that thing' so they can feel a hint of intensity-relaxation and for thought activity to stop.
I can't help to think that is so convenient to arm theories and ideas like one has bad brain chemistry to justify the fact that you are by-passing the natural recompense mechanism of survival crude humans are, but you just don't want to recognise that?