Circadian Rhythm Linked to Bipolar Disorder

Research with mice offers first insight into possible connection.

By Amanda Gardner
HealthDay Reporter
Tuesday, March 20, 2007; 12:00 AM

Copyright © 2007 ScoutNews, LLC. All rights reserved.

TUESDAY, March 20 (HealthDay News) -- A gene involved in regulating circadian rhythms -- daily rhythms, including the wake/sleep cycle -- may also play a central role in the manic phase of bipolar disorder.

Mice with a particular mutation in the CLOCK gene, which is central in regulating circadian rhythms, displayed behavior very similar to manic behavior in humans. Given lithium, a drug used to treat bipolar disorder, the mice returned to many of their normal behaviors.

The findings could serve as a launching point for further research into bipolar disorder, whose mechanisms continue to elude scientists.

"It gives us a really nice model of mania to be able to study how mania develops and how the treatments for mania work, because a lot of the actions of mood stabilizers have been a mystery," said Colleen McClung, study senior author and assistant professor of psychiatry at the University of Texas Southwestern Medical Center at Dallas. "Bipolar has been difficult to study."

David J. Earnest, a professor of neuroscience and experimental therapeutics at Texas A&M Health Science Center College of Medicine, added: "It really does provide something beyond an associative or correlative observation that circadian rhythms are disturbed when patients are experiencing bipolar disorder. In this animal model, this mutation in the CLOCK gene produces behavioral patterns which are very similar to bipolar disorder."

Scientists have long suspected that circadian rhythms might be involved in psychiatric disorders, particularly bipolar disorder.

Bipolar disorder is characterized by alternating swings of very high and very low -- or depressed -- moods, along with changes in energy and the ability to function. About 5.7 million American adults, or about 2.6 percent of the population 18 and older, may have bipolar disorder, according to the U.S. National Institute of Mental Health.

Almost all people suffering from this disorder also have irregularities in circadian functions including sleep/wake, hormonal, appetite and body temperature. Major disruptions in the sleep/wake cycle can trigger a bipolar episode. And many of the treatments for bipolar disorder, such as lithium, can shift circadian rhythms.