Bryan Caplan has written a few times about why he believes mental illnesses are ‘socially disapproved preferences’. His view is that you can distinguish a preference from a constraint with the gun-to-the-head test: “If suddenly pointing a gun at alcoholics induces them to stop drinking, then evidently sober behavior was in their choice set all along.”
Caplan's arguments have always looked to me like they're confusing the map for the territory. The distinction between budget constraints and preferences comes from our economic models of consumer choice, which we use to try to explain and predict how consumer actions affect various important variables in the aggregate. These models are good, and very often very helpful - but they remain models, and (after all) all models are wrong. And one of the ways they are wrong is that when you break down the aggregate and look at specific cases of consumers making choices, their decision-making isn't easily factored into preferences (on the one hand) and budget constraints (on the other). Mental illness is just the clearest example, but human psychology generally is quite messy in ways that don't fit into simple models of decision-making. That's not to criticise those models: in many circumstances they can be useful both descriptively (they're approximately correct, and this approximation gets more correct as we aggregate examples) and normatively (they tell us how we should be thinking, rather than how we actually are thinking). But Caplan is just refusing to admit that this model isn't the exact truth, demands a clean and sharp distinction between budget constraints and preferences, and then - upon noting that mental illnesses aren't budget constraints in the idealised spherical-cow sense demanded by his model - concludes that they must purely be preferences.
This seems like it's reaching towards the best response to Caplan's position that I've seen, which is that most mental illness works as a budget constraint. People with these mental illnesses are still able to do the things their conditions inhibit, but it's harder and costs them more, and they'll run out of resources sooner than a more healthy person would.
Similarly a lot of people in wheelchairs could, exhaustingly and painfully, walk 50 feet if you put a gun to their head, But if you tried to make them walk 5 miles you'd have to shoot them.
A point of clarification:
For many (most?) adults with ADHD, it's not doing the activity that is difficult, it's starting the activity.
In fact, many of the most effective non-medicinal interventions are clever ways of metaphorically pointing a gun at one's head in a way that convinces the brain that the threat is real.
If a neurotypical person has a paper due tomorrow, the thought of it being late is enough to overpower their preference against doing it. But someone with ADHD needs a much higher threshold of threat to overpower the same preference.
Does that mean that ADHD is stronger preferences in the face of the same threats, or does it mean that ADHD is a higher tolerance to threats in regards to the same preferences? I don't know, but it seems both are reasonable.
This reminds me of the Schopenhauer quote "A man can do as he wills, but not will as he wills" this seems true in the short term and as tautology, but if you consider the method of building habits and frameworks that change people's preferences and perceptions (Such as how exercising every day for a month makes you *wish* to exercise on the 31st day, or how by changing organ donation decisions from opt in to opt out, people's "revealed" preferences changed greatly) then the claim seems more dubious that mental illnesses like ADHD are something we exercise no will over. I think there is likely just a change in how we exercise "will" in different timescales. If you took every person with depression and put them through a rigorous boot camp focused on getting their bodies and minds into the best shape possible over a summer, I'm sure that at least some of them would walk out of that boot camp feeling cured. I think that will color different people's opinions on the subject differently, so I'd be interested to hear other takes