Thank you for writing JA with your concern.
This is a common dilema for family members of a person showing a mental condition or brain disorder. I am familiar with this and will discuss a few things with you.
There are no real medical tests to give a definate cause of psychosis. Of course routine labs, etc., done initially to make sure there is no physical problem (like mania with psychosis from hyperthyroidism) But if there is no physical problem like this, then there are no specific medical test that can be done to say, yes this person has schizoaffective disorder or yes this person is severe depression with psychosis, or bipolar in the manic stage with psychosis (these are some of the psychiatric diagnosis that can include psychosis).
Diagnosis is determined by knowledge of the specific guidelines. These guidelines are in the DSM IV revised (diagnostic and statistical manual of psychiatric disorders). The diagnosis is decided upon after getting history, interviewi and observation of the patient. The final diagnosis is given by the Psychiatrist, although Psychiatric Clinical Nurse Specialist (CNS's or NP's) and Psychologist may be involved in interviewing and testing to obtain data to make the final diagnosis.
Medications and therapy or a combination are helpful. In the past 20 years new medications have been created which treat psychosis in a much more efficient way. 20 years ago these meds still caused severe side effects often, such as extreme weight gain. In the last 5 or so years, medications have been developed that do not cause these weight problems.
There are several different medications to use. The doctor will try one usually for about 3 months. Sometimes more than one type of medication is needed, depending on the patient's symptoms. Sometimes we are lucky and the individual does well with the first medication regimen. But it is also fairly common in the beginning of getting a young person on a good regimen to have to try more than one medication. It takes patience, because of yet, there is no way to know which medication will work the best, ***** ***** 5 choices. Work and research is continually being done to improve this issue.
Once a medication regimen is found, it is important for the patient to follow up with the doctor closely. That way if there are side effects, the doctor can make an adjustment. Sometimes a patient feels so good again with the medication they will quit, this is of course not recommended. In fact, it can be harder to stabilize a person if the have repeated times of going on and off medications - for some reason the medication may not work as well. This is different than medications for other things. These medications are changing the neurochemistry of the brain so they must be continued - and if there is a need to decrease a medication it will be important to do it with the doctors assistance.
There is an organization called NAMI. It was started by family members in similar positions as your family. This organization is well respected, and besides the offering of support for family members of the mentally ill, and the mentally ill themselves, they have even lobbied successfully for things like parity in insurance (meaning that insurance must treat mental illnesses as a biological disease, just like other diseases and pay for treatment equally).
Here is the national web site: http://www.nami.org/Hometemplate.cfm
There are links so that you can find support in any area that you live in. They have numbers to call so that you can find out about resources in each area. For example, commitment laws in that specific state, recommended psychiatrist, etc. They also provide support groups for family as well as the patients. This is helpful for education about what is going on with the individual and learning about disease processes and the best way to help. The web site is one of the best for information about these disorders as well.
As far as what to do with the niece, there are also teen support groups through Nami that would be good for her. But at her age, 15, she will need someone to help her, because basically right now her mother needs to be taken care of.
I hope this helps some. Fell free to ask questions or discuss in a reply.