Whatever the origins of somebody's substance abuse problem, at some point you have a responsibility to do what your doctor tells you to do if you want to receive a check, and doctors almost never tell people to go get street drugs. Part of asking for a disability check is telling us the condition is serious, and I think it's reasonable to use substance abuse as a gauge of how serious somebody actually thinks the problem is. If somebody has done cocaine until he has chronic cardiomyopathy, and has figured out in the process that cocaine is a bad idea, cocaine obviously doesn't continue to change his medical condition and his heart is still a wreck. The guy who keeps snorting it and goes to the hospital every other week with another myocardial infarction has as good as told us he doesn't really think the heart condition is anything to worry about and I'm going to let his actions speak louder than his words. There are an astonishing number of diabetics who decide they didn't need to waste time and money on insulin or test strips, preferring to spend the money on two packs of cigarettes a day and a steady supply of Cheetos, then use a fifth of liquor to anesthetize the peripheral neuropathy. There are a lot of bipolar folks out there who will take pretty much any drugs except the ones their doctors want them to. I know manic bipolar folks don't want pills because they feel great, and I know psych medicines generally have some of the worst side-effects, but self-medicating with meth is actively working against your health-care provider. If somebody has a disabling physical or psychological condition and actively interferes with his doctor's treatment plan by choosing to take drugs, he is not making an honest effort to comply with treatment. On a fundamental level, what's the difference between paying these people and paying somebody because he can't see without his glasses?
Now, doctors do occasionally tell chemo patients that a little weed for appetite stimulation isn't a bad idea. A couple of other situations they'll treat similarly. The double amputee getting drunk once in a while is different than the guy with cirrhosis doing the same. All that is admittedly true. But as a general statement, we're not talking about otherwise healthy people making decisions with few long-term complications here, we're talking about people who have told us they have a condition which absolutely controls their life to the point they can't hold a job, and they want us to help them out because the condition truly is just that terrible. That's a claim worth taking seriously and examining earnestly. But if the condition is that terrible, and they're actively working to gamble on making it worse for no apparent reason, isn't it reasonable to ask how much it really bothers them?
Honestly, Alexander's rats are interesting, and there's a lot to be learned there on addiction generally, but I'm not sure they're entirely germane to a discussion of disabled people abusing drugs. Almost without exception, their choices on substance abuse were made before the disability began or at latest with the incident associated with their disability being a "wake-up call." You do see some get too attached to painkillers in the process, but they're still a minority. Mostly, that pattern is set long before they get near the disability process.
And I don't want to unfairly pick on diabetics, bipolar people, or cardiac patients, and make it seem like I think they're all loser junkie grifters out to bankrupt the world and corrupt our precious bodily fluids or whatever. There are a lot of each of those out there, so they'll be well represented in both good and bad examples.
