Doctors don't completely understand the causes of bipolar disorder. But they've gained a greater understanding in the past 10 years of the bipolar spectrum, which includes the elated highs of mania to the lows of major depression, along with various mood states between these two extremes.
Experts do believe that bipolar disorder often runs in families, and there is a genetic component to this mood disorder. There is also growing evidence that environment and lifestyle issues have an effect on the disorder's severity. Stressful life events -- or alcohol or drug abuse -- can make bipolar disorder more difficult to treat.
A multitude of controlled studies of bipolar patients and their relatives have shown that bipolar disorder does run in families. Perhaps the most convincing data comes from twin studies. In the studies of identical twins with the same genes, scientists report that if one identical twin has bipolar disorder, the other twin has a greater chance of developing bipolar disorder than another sibling in the family. Using statistical data, researchers conclude that the lifetime chance of an identical twin (of a bipolar twin) to also develop bipolar disorder is about 40% to 70%.
Along with a genetic link to bipolar disorder, research reveals that children of bipolar parents are often surrounded by significant environmental stressors, such as living with a parent who has a tendency toward wide and unpredictable mood swings, alcohol or substance abuse, financial and sexual indiscretions, and hospitalizations. Although not all bipolar offspring will develop bipolar disorder, many children of bipolar parents do progress to an entirely different psychiatric disorder such as ADHD, major depression, or substance abuse.
Some findings show that people with bipolar disorder have a genetic predisposition to sleep-wake cycle abnormalities that may be responsible for triggering the symptoms of depression and mania.
The problem for those with bipolar disorder, however, is that sleep loss may precipitate a mood episode such as mania (elation) in some patients. Worrying about losing sleep can add to cognitive arousal and increase anxiety, thus worsening the bipolar mood disorder altogether. Once a sleep-deprived person with bipolar disorder goes into the manic state of elation, the need for sleep decreases even more.