Actually, I remembered that there are relevant results from clinical studies that are available. Here are the side effects of OxyContin.[1] (Euphoria is considered a side effect.) The most commonly-reported side effects were constipation, nausea, and somnolence. If you look down further, you can see that both euphoria and dysphoria were reported rarely.
[1] http://www.rxlist.com/oxycontin-drug/side-effects-interactio...
Re:Opium, Empire, and India
by opiate_eng on Wednesday April 05, 2017 @08:14PM
(#14046879)
They already do these studies to test opiates vs other painkillers. Opiates kick ass.
Or maybe you're right: they just take away pain. But it turns out a lot of us have existential pain so it works all the time.
One could easily resolve the question of whether opioids cause euphoria by doing a double-blind clinical study. I would love to do that study, in fact.