Yup.
It's called being an addict.
You know we actually have changed the way our DNA functions? I can't remember the names of it off my head, I'll look for it, but we've altered the way our DNA functions and don't produce enough of a number of various chemicals that make a "normal" brain feel pleasure and pain. Is not all dopamine related but it plays a part. It takes 1-2 years of abstinence for it to get used to not having foreign chemicals introduced for our DNA to learn how to behave.
I'm simplifying it because I don't fully understand it and only read about it once or twice but I found it interesting. I'll see if I can find some lit on it because now I want to educate myself so I'm not completely talking out my ass.
Basically all addicts are born in pain.
Pre and post natal exposure to stress hormones produced by the individual and their mother causes the Toll Like Receptors (TLR) to malfunction, especially during stress and puberty (lots of hormones flyin around) but this continues all your life, be you 5 or 50. That's why quitting opiates isn't actually fixing anything in your brain.
Getting clean from heroin is like cleaning a kitchen and thinking your kids aren't gonna mess it up ever again. Things can be done to mitigate such as gym, healthy diet. But eventually it will be a mess again.
TLR4 in particular causes proinflammatory cytokines to be produced. These cytokines, in particular TNF-a (there are many others) bind to receptors in our brain, in particular in the Mu an Ku (opiate receptors) in the PAG, and gabba receptors. These chemicals in low level cause anxiety, depression and even joint pain and stomach problems, especially during stressful events.
Those exposed to physical and emotional abuse, be they rich or poor are born like this, primed, predisposed. They are born into pain but don't realise that its abnormal to be anxious and depressed.
So when exposed to opiates, and everyone will always end up getting exposed, one day finally you are relieved of a weight you never realised you were carrying.
When i was 14 I had my first shot. I thought the high was amazing.
What i was really feeling though was the giddy relief of life without pain. It was as if 100kg had come off my back.
This pain cant be fixed with panadol. Unless you want to be at gym junkie levels (literally producing a ton of endorphins, opioids that bind to Mu ans Ku) there are no easy solutions.
Heroin works well. But here is the kicker.
Heroin, morphine etc have two metabolites, M6G and M3G. The first relieves pain.
But the second, the M3G causes a problem. It activates, ironically enough, TLR4.
So your body makes more cytokines, so to stop them hitting your gabba, Ku and Mu you have to take more heroin hence tolerance.
Until the day you run out. And then your exposed to insane levels of toxic proinflammatory cytokines. The pain is like the flu x 1000.
Think of the worst pain you've ever had and times it by 100 and a tell me if you could last a week
The point of these cytokines at elevated levels, they make you vomit, give you fever and attack infected tissue, causing pain on a huge scale but killing the infection as well.
Nominally TLR4 is activated by signally from white blood cells. But for addicts, be you a meth head, drunk or a junkie those three drugs all cause, to certain degrees TLR4 to be activated.
Opiates more so.
This is why drugs are addictive and why getting clean is almost pointless