It's been awhile since I've read these, but some interesting sources on the conditions of 20th century Psychiatric Institutions, and influenced some of the reforms or attempted reforms to Psychiatric facilities. Michel Foucault and Erving Goffman are two notable people who have written extensively on the subject, and the 1960s saw the rise of more awareness to the horrible conditions of Psychiatric Institutions as various developments in Psychotherapy and Psychopharmacology were transforming some aspects of treatment - it would still take most of the 20th century to develop a better understanding of how to treat the the mentally ill.

Actual institutions or Psychiatric hospitals declined throughout the period you mention, in part due to reactions to the maltreatment of patients and forced institutionalization, and thus funding for these hospitals dried up. The history of psychotherapy (for which I include drug therapy) during the second half of the 20th century saw various ideas competing for, and challenging the traditional practices of throwing someone into a "lunatic asylum." After Freud, there were Behavioral views (a very scientific approach), Cognitive (A mind-oriented approach), Humanist (A person-oriented approach), and Psychiatric (A brain-oriented approach - these included various surgical methods, such as lobotomies, drug-therapies, shock therapies, etc). By the mid '90s, the merits of all these methods of treatment for various conditions had begun to be the primary means of treatment in a combined, mulch-dimensional approach with less emphasis on Psychiatric Hospitals and Institutions that isolated (and while outside the purview of this sub, problems exist to this day) people from society.

As I mentioned, if you want to look at how Psychiatric Institutions have changed, the 1960s offer a great deal of insight and critics of the system. David Cooper wrote a great deal in the late '60s against the-then standard practices of psychiatry. Unfortunately I do not have a source from a patient, but there are many or some compiled works that show accounts. Thomas Szaz is another influential source on this subject.

Hopefully someone else has an answer about the conditions and status of these hospitals by the 1990s, as my knowledge is from earlier periods and the anti-psychiatric movements of the 1960s, and more contemporary issues that are not within the scope of this discussion.

A side note, President John F. Kennedy's sister Rosemary was one of the first victims of prefrontal lobotomies, ordered by their father, and generally kept isolated from everything afterward, due to how it made her extremely disabled, intellectually and physically, and highlights one aspect of the coercive and abusive nature of both psychiatric institutions AND the pervasive attitudes toward mental illness and those who suffer from it

Advocacy groups and people who had been involuntarily forced into psychiatric hospitals have been a large part of the anti-psychiatric political movement, with these patients-rights groups taking shape in the '80s and '90s especially. Some of these groups identify as "survivors" of this system, and would provide perhaps a good start on the individual experiences you're looking for.

Societal views on mental health, illness, the body, and the cultural attitudes toward both the illnesses and those who suffer from them are a major aspect of how and why these Institutions developed in the first place - and, if you want to learn more about the nuances beyond America and western Psychiatric treatment, there has been a fantastic amount of research done within the last couple decades. I'd also recommend checking out the history before 1950, as it's quite difficult to understand just how such practices came to be accepted without knowing how it got there in the first place. Before nuanced understandings of mental illness developed in the beginnings of the 20th and end of 19th century, lunacy and insanity were broadly and widely condemned.

Anyway, this got to be far too long, and I don't know if I was too helpful as it's a difficult question to answer, and I dont have any of my books on the subject close at hand right now. Some of the vocal critics I mentioned should give a start, as they certainly outline the conditions prevalent in their time. Gay and lesbian movements in the '60s onward definitely helped highlight other abuses, such as Homosexuality being a part of the DSM for a very long time, and regard as a mental illness. Suicide being illegal and a felony in the US shows another side of this entire mess, though by the 1950s states were decriminalizing it - and by 1990s, and only two had any laws against it, which were eventually removed. Yet that's extremely recent and reflects societal views and stigma of mental illness, with suicidal harm being a justification to involuntarily hold a person in psychiatric care or worse.