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This all depends on the context of the question. In the normal every day context, once someone is diagnosed as bipolar
, it is assumed that they'll be dealing with it for the rest of their life. It doesn't mean that the disease is always active, but the person needs to monitor it. There are people who are able to go off medication for a period of years and then might need to return to it, but there are also people who are misdiagnosed as bipolar during one period of life and it never really pans out in the typical way. In those cases, it was usually some subclinical manifestation of another illness and misdiagnosed.
In the strictest of medical/legal terms a person is diagnosable as bipolar when they meet the diagnostic criteria set forth in the Diagnostic and Statistical Manual, which requires a person to have the mood symptoms for more than six months. They can be sub-coded as in remission (bipolar, in remission) for years without any active symptoms.
Another side is that many bipolar patients loathe to take their medication, so they take it irregularly and this causes the highs and lows to return. They usually stop the meds when they feel like "I'm not really bipolar". This would still be diagnosed as active bipolar disorder.
Thyroid issues can mask bipolar, and they can imitate some bipolar symptoms, so with all that said, it's probably equal chances that the person has it or doesn't, based on what you've said.
My best to you.
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