Researchers may be one step closer to cracking the code of manic episodes of bipolar disorder in humans, thanks to the recent findings dealing with the mutation in a specific gene in mice.

Research has revealed that a gene that regulates our internal clock may play a crucial role in the manic phase of bipolar disorder.

Mice that had a particular mutation in the CLOCK gene - the one that regulates the circadian rhythms, including the daily rhythm and the wake and sleep cycle - displayed manic behavior not unlike that in humans with bipolar disorder. However, once these animals were given lithium, a drug used to treat bipolar disorder, the mice adopted a normal circadian rhythm.

According to Colleen McClung, the senior author of the study and assistant professor psychiatry at the University of Texas Southwestern Medical Center (Dallas), this may provide a clue for further study of manic episodes of bipolar disorder in humans. '[A] lot of the actions of mood stabilizers [the traditional drug used to treat bipolar disorder] have been a mystery,' she noted. 'Bipolar [disorder] has been difficult to study,' she added.

These findings confirm what many scientists have long suspected. Many have felt that circadian rhythms might somehow be involved in the development of bipolar disorder, but just could not prove it.

Nearly every individual who suffers from bipolar disorder also has problems with his sleep cycles, appetite and body temperature. In fact, it has long been noted that disrupting a patient's sleep cycle can trigger an episode.

The study appears in the Proceedings of the National Academy of Sciences.

Interestingly, with the mutation in the CLOCK gene, the mice exhibited symptoms very similar to humans experiencing the manic phase of bipolar disorder. The laboratory animals displayed greater hyperactivity, were more likely to 'take risks' and showed a preference for 'reward' substances, such as sugar and cocaine. Moreover, the mice displayed less depression.

When the researchers then placed a functional CLOCK gene into the mice, they found that some of the manic behaviors were corrected.

Bipolar disorder affects nearly 5.7 million people in the United States alone. Caused by a chemical imbalance, bipolar disorder is treated with a combination of mood stabilizing medications and psychotherapy.