What menatl disorders constitute long-term care in a psychiatric hospital (insane asylum)?

Early asylums were designed to hold people who were 'insane', but obviously that sort of definition doesn't hold up these days. What sort of mental disorders constitute commitment to a psychiatric hospital for long-term care, and what type of care would they receive?

Generally its any condition that makes the person at risk of harming themselves or others.

all of them

they only lockup those who pose a threat or have unrealistic views plus the ones beyond the abilities of your counselers and to adjust meds

A severely unstable person suffering from bipolar with EXTREME mania, or a mixed episode that has become out of control. I am not exactly sure what constitutes "long term," but you would be restrained and on strong antiphsycotics until you are more sedate. Confinement and supervision would be necessary.

Of course, there are lots of others. That is the one I know about.

We don't have insane asylums anymore. If by long-term you mean years, we don't have that, either, unless you mean psychiatric prisons. Most care is limited to months. If one can't make on their own, they are transitioned to half way housing, at least in my state. The illnesses that most often fall into this are schizophrenia and schizoaffective disorder, perhaps advanced bipolar disorder or refractory depression. The latter two much less so to my knowledge. There's probably a smattering of other MIs but they probably include some of these four. The other consideration is that all of these illness have very high suicide rates. So, ya know, the older ya get, the worse it gets, the higher the odds for self-selecting out. And, of course, there's the new asylum called The Street.

The things that would necessitate long term care in a psychiatric hospital would be, Schizophrenia, medication resistant depression, multi-personality disorder. Some eating disorders some times bi-polar disorder if medications don't work and there are other's I can't think of right now. The one that most people are familiar with would be psychosis where you lost touch with reality for what ever reason.

Any mental illness can end up in psychiatric admission, if you hurt yourself or someone else seriously, or are showing very worrying behaviour, or are threatening suicide in a strong manner.
Although there are some disorders that you cannot be hospitalised for.