... I mean, on what are you basing this assumption? Mass psychiatric institutionalisation has been phased out pretty much everywhere at this point; if your thesis is correct, how do you explain differing rates of homelessness (and in particular unsheltered homelessness, where the US more or less leads the developed world) between the US and other developed countries? Like, it seems more likely to be some other factor.
Ireland, for instance, had the highest rate of psychiatric institutionalisation in the western world in the 60s (some Warsaw Pact countries were likely higher). It was rapidly phased out in the 80s and early 90s. Homelessness (though a persistent problem since the 19th century) remained rather low until the early tens, then rose rapidly. I've never heard of anyone attributing this to the mental hospitals closing 30 years previously (this seems to be a uniquely American belief); it is generally attributed largely to _shortages of housing_ (itself due to the near-total collapse of the construction industry for a decade after the financial crisis).
The issue in the US isn't lack of institutionalization, per se, it's the lack of mandatory mental health treatment. That is, it's very difficult and rare to require the mentally ill in the US to take medicine, even after repeatedly demonstrating an inability to control their conditions or even to take basic care of themselves. For one thing, there was an overcorrection in civil rights law that makes it difficult to establish a mandatory treatment plan. Secondly, because of lack of institutional beds and a will to use them, there's little backstop even for the few patients that are on court-ordered treatment and fail to comply.
While most countries have deinstitutionalized, they still make it much easier to force treatment on an out-patient basis. (This is true of drugs as well, which is part of the reason "harm reduction" often works better in Europe--a credible threat of involuntary hospitalization.) This was the original plan in the 1970s in the US, to transition to out-patient care, but it didn't pan out. The mental hospitals were closed, but rather than shift the funding to out-patient clinics and treatment, the funding was simply pulled altogether. And because of the civil rights law overcorrection, addressing this is more than simply re-establishing the funding. California, for example, restored hundreds of millions of funding in the past decade, but for various legal and inertial reasons, cities and counties simply won't force treatment plans on even the most desperately ill patients, even when they're harming themselves or others. Sadly, we're slipping back into using the penal system to house the mentally ill; there's much less political and institutional pushback than increasing the use of conservatorship and civil commitment.
The problem has been well understood for more than 40 years. Here's a 1984 piece from the NY Times that could be written the same today: Richard D. Lyons, "How Release of Mental Patients Began", https://www.nytimes.com/1984/10/30/science/how-release-of-me...
> While most countries have deinstitutionalized, they still make it much easier to force treatment on an out-patient basis.
Where are you getting that? Which countries? Certainly in Ireland and the UK, I'm pretty certain that it is all but impossible to force outpatient treatment, and I think this is generally more or less the case in Western Europe as a whole. Involuntary admission to psychiatric hospitals is still, marginally, a thing, but very rare.
If you're wondering why human rights treaty organizations are so involved with these laws, and with the similar laws concerning children, look up how the holocaust started. But ... you don't really want to know the connection there.
Ireland, for instance, had the highest rate of psychiatric institutionalisation in the western world in the 60s (some Warsaw Pact countries were likely higher). It was rapidly phased out in the 80s and early 90s. Homelessness (though a persistent problem since the 19th century) remained rather low until the early tens, then rose rapidly. I've never heard of anyone attributing this to the mental hospitals closing 30 years previously (this seems to be a uniquely American belief); it is generally attributed largely to _shortages of housing_ (itself due to the near-total collapse of the construction industry for a decade after the financial crisis).