This is one of those phenomenon that no one is tackling as to what to do, but in real life practice, it happens and when it does, no one wants to touch it.
MR patients, children, people in nursing homes, autistic patients, etc, sometimes, just like all human beings, they act out. When they act out, especially while in the care of someone earning a small income (e.g. child-protective services, nursing homes, etc), that caretaker usually doesn't know what to do and drops them off to the hospital. The hospital then drops them to the psychiatrist.
So okay, now they're in your lap, what do you do? The answer (IMHO) is actually quite easy though because no one's happy with it it doesn't seem like it's the right answer.
I try not to medicate them unless there's reason to do so. E.g. I had an MR patient in the hospital that was crying because she broke up with her boyfriend. Geez, most people break up in things like that. What am I supposed to do? Not suicidal, not homicidal, crying was within a cultural norm. I wrote that on my note and discharged her.
Okay, autistic patient, no homicidal, not suicidal. What's the least restrictive safe environment? You send them there. Usually it's back to where they came from. Yeah, the caretaker will be pissed with you, but guess what? Usually the caretaker just wants to you take the patient off their hands by admitting them or zonking them out with meds in a manner that is not therapeutic for the patient (but it makes the caretaker's life easier). Our job is to treat mental illness, not to make the jobslof people who make less than $10 an hour easier.
Or how about the kid that because of the Columbine-induced scare on teachers, now sends almost any kid to the ER. E.g. "This child wrote a poem about the death of his grandfather. Obviously he is very saddened by this." Me...."This child shows no evidence that meets reasonable medical certainty that he is homicidal or suicidal. Sadness over the death of a loved one is within a cultural norm. After social workers talked to his family, they told me they had no reason to believe he was dangerous to himself or others and quite frankly are upset that he was sent to the hospital."
Discharge.
Okay, now that about takes care of about over 50% of these types of cases. The rest become hard. You will sometimes gets patients that are in a grey area where you cannot decide. In these cases, some doctors will admit the patient so more time can be given to determine the best disposition. Another problem I've encountered is I'll want to discharge a patient, but then the caretaking facility refuses to take them back, in effect dumping them to the hospital. What are you supposed to do then? It's not ethical or legal to admit a patient simply because you can't find housing for them, but what about situations where the patient cannot care for him/herself?
In cases like this, I'd talk to the social workers and hospital administration about what to do in these situations. A lot of this I'm sure will depend on the state and local services.