A complete fallacy.
A word created by weak willed people for weak willed people to use as a way of avoiding
responsibility for the things they do that they're not proud of, but continue to do
regardless of the damage it causes.
Most likely created by psychiatrists who wanted a word they could use as a scapegoat, to hide their own
shortcomings.
One of my pals, whom I've known since school, didn't
have the balls to say, "No!" to my other idiot friends when they offered him drugs for
the first time and even though his teeth are now brown/falling out, his breath stinks and he has no
real friends anymore, he will continue doing drugs and when people ask why he's such a dumbass, he'll just say, "It's not my fault, I'm an addict!" and people will accept that at face value because they have been taught/fed that "Addiction" is a real phenomenon and they cannot tell the difference between a chemical dependency, habitual obsession or self-medicating.