What about patients who unknowingly become addicted to painkillers through no fault of their own? Tramadol, for example, is a sub-opiate that even in a small dose once a day can cause dependence, as the doctors euphemistically call it. Are these people addicts too?
Absolutely. As pointed out, not every case involves choice - as with fetuses who are addicted in utero due to the taking of drugs by their mothers. You could addict a child to alcohol or drugs by simply feeding it to them without them having the cognitive awareness that they were becoming addicts. And, in the case you describe of opioid use starting out as pain treatment that turns into addiction.
These are all still cases of addiction and are not a "disease."
There's controversy with dependence vs addiction (specifically with marijuana which is classified as not being physically addictive, but users can develop a psychological "dependency" upon it). With true addiction the brain's neurotransmitters lock onto the substance and the feeling becomes one where the body feels like it
needs the substance to function, to feel "normal" or to even survive. The feeling is erroneous, but no less real.
A lot of this argument is tied to semantics. We can call a lot of things "addictions" (such as behaviors that do not involve consuming drugs), but these are actually habits, obsessions or compulsions (getting us into the whole realm of psychology).
There is a thin line, however - if we look at things like Internet or social media addiction (which we're engaging in right now) - studies show that for some people the behavior triggers releases of dopamine in the brain - the same substance that is produced in the brain by many addictive drugs. So the ultimate effect becomes the same - the Internet addict gets their fix, begins to feel the high of dopamine (or what to them has become a feeling of okayness or normalcy) and after a while comes to rely on continuing this feeling.
So, is Internet addiction an addiction or a disease?