Looking for advice about split personalities.

How old are you and the person you are caring for and how are you related? It helps knowing this to help give u the best answers.

You mention in ur profile the person has a Dementia? Have they been formally diagnosed? Meaning, do you know exactly what type of Dementia they have? Alzheimer's, Lewy Body, Vascular are a few main types. If you do know what type, research it for symptoms. A lot of members recommend the "Teepa Show" where she explains how to deal with and understand those suffering with Dementa.

Yes, there is "sundowning" that occurs late afternoon early evening. Some have posted it lasts till bedtime. There is "showtiming" where they can muster just enough energy to seem normal (like in front of their Dr) and then crash later. Its a very unpredictable, and that is why those suffering from it should not be alone. The brain is dying. As it hits each part of the brain, that part dies. Eventually it will hit the part that controls breathing and heart. When that dies, so does the person. Go on Youtube and search for Akzheimers videos. There is a very good one where its a cartoon with a yellow brain. It takes you thru the stages of ALZ but I found it very good with Mom and she did not have ALZ.

This is the place you can ask questions and even just vent so welcome.

It’s now “called” DID, aka Dissociative Identity Disorder. It is “very” rare. Most people “who” are diagnosed have “had” severe childhood trauma.

split personalities are very rare. They can only be diagnosed by a psychiatrist.

Your profile says your loved one has dementia/ALZ. Perhaps it would help you to learn more about this disease, and how it changes our LOs, why is changes them, what it looks like in their personalities and how to change your approach in dealing with them so that your daily interactions are more productive and peaceful. Teepa Snow has many excellent videos on YouTube that I found very informative and helpful.

Was the person you're referring ever actually diagnosed with a personality disorder by a psychiatrist? If so then they need to be on some serious medication to keep the "personalities" in check.
Have they been assesed and diagnosed with Alzheimer's or some other form of dementia?
Or are they a now elderly person which you have a long and dysfunctional history with who often behaved abusively to you when they weren't elderly?
The answer to whether or not you can 'predict' the behaviors is a partial 'yes'. If the person flips out daily in the late afternoon/early evenings that sounds like sundowning. Anti-anxiety medications can help tremendously.
Does the person you care for put on "performances" like panic attacks, hyperventilating, health crises/emergencies (that are no emergencies at all), and treat only you with negativity and verbal abuse? Yet they are nice as pie with anyone else, and are fit as a fiddle with no complaints when they're sitting in the doctor's office? The treatment and remedy for this is to completely ignore them and pay no attention whatsoever (as far and safe as it is to do so).
Even with dementia and some cognitive decline, a person will reserve certain behaviors for certain people and you would know if you are such people.
I've found working as a caregiver to elderly people for many years most with some kind of dementia or other, that giving and witholding attention based on behavior is very effective.
If you notice a sudden change in behavior with the elderly, getting them tested for a UTI is important. Many times it's the reason for the sudden change.

Welcome, Enquiry!

Are you caring for a person with dementia who has fluctuations in her/his ability to function?

That's not split personality.

If the person in question become combative in the late afternoons, that called "sundowners".

Folks with dementia who suddenly start exhibiting extreme behavioral changes often have UTIs or other infections.