The "Rat Park" study indicated the material circumstances of the rat was the major determining factor on whether he/she became an addict. The rats alone in a little cage OD-ed on the morphine water, while the ones with lots of space to run around, ground to burrow in, plentiful food, other rats to socialize and mate with, etc - i.e. who basically had all their basic physical and psychological needs met - took a drink of the morphine and then chose normal water. Gabor Mate has emphasized that suffering abuse as a child is also a good predictor of future addiction.
Which makes sense. That's why putting addiction down to the strength of will of the addict might not be the most accurate or politically progressive interpretation, and tends to be the default of a doctrinal system owned by those putting the rats - i.e., us - in small isolation-cages and supplying them with lots of morphine water. And why we should avoid repeating the meme.