There’s tremendous variability in how bipolar disorder changes or progresses through the years. Finding studies that can give definitive answers is difficult, because most research focuses on people with recurrent mood episodes, and those who have had few episodes are harder to track. In general, we can break this question down into three groups of people. Those who get better, those who get worse, and those who stay about the same.
First, there are some with bipolar who have had long periods between episodes. Or perhaps they only had episodes in their twenties or thirties. Often these are people whose mood episodes were clearly related to specific stressors such as drugs, child birth, etc. Many of these people will continue to have significant symptom-free periods, minor episodes, or no further mood episodes at all.
For others, the course is more challenging, and progression to the rapid cycling variant of bipolar disorder is common in later life. There are a number of hypotheses as to why this is. For example, is it just the natural course of things, or is it the product of antidepressant induced acceleration, or diminishing sensitivity to mood stabilizers, or the additive effects of co-morbid medical conditions? The answer is not known.
Finally, there is a third group that continues to have mood episodes, but they do not progress in frequency. In this group we find a large number of people with bipolar disorder who have effectively learned strategies to diminish both the frequency and severity of their episodes.