In measuring whether the number of bipolar episodes increases with age, the age the disorder first appears is more important than the effects of aging.
A study that looked at outcomes 20 years after the age of onset of bipolar disorder found that the frequency of depressive episodes often increases over time, while the frequency of manic episodes does not.
However, the amount of time spent in episodes of depression has more to do with the age of onset of BP then the current age of the individual with BP.
The implication is that while depressive episodes may increase with time, the contributing factor may be age of onset of a person’s struggles with bipolar disorder, not the cognitive decline or physical effects of aging.
People with an onset of BP under 30 years of age saw an increase in the amount of time spent in depression during the third, fourth and fifth decades after onset. People first hit with BP over the age of 45 had rates of depression that remained stable.
At 20 years after onset the people who were struck with BP under the age of 30 spent 30% of their time depressed. The people with an age of onset over 45 faced depression 22% of the time.
There was no indication that the severity or duration of episodes of depression increased. They just occurred more often in people with an earlier age of onset.
The amount of time spent manic or hypomanic remained stable despite age of onset or number of years after onset, even in individuals with bipolar disorder 1.
While it seems obvious that the longer one has bipolar disorder the greater the number of depressive episodes, the researchers suggest that people with an earlier onset of the disease suffer from more depression because their BP developed concurrent with the stress of the enormous life changes of early adulthood.
Simply put, the brain develops until age 25. Mental illness that emerges in a brain that is still developing will result in a more challenging prognosis than illness that begins in a mature brain. And the impact will be multiplied as years pass.