Washington, July 1 (IANS): Poor sleep is associated with negative mood in women with bipolar disorder, says a new study.

Bipolar disorder is a brain disorder that causes unusual shifts in mood, energy, activity levels and the ability to carry out day-to-day tasks.

The condition is marked by extreme mood episodes marked by manic highs, depressive lows or mixed.

Sleep problems are common in people with bipolar disorder -- and poor sleep quality and bipolar disorder appear to exacerbate each other.

"Patients with bipolar disorder often suffer with sleep problems even when many of their other symptoms are well-controlled," said Erika Saunders from department of psychiatry at Penn State College of Medicine.

"Improving their sleep could not only better their quality of life, but also help them avoid mood episodes," Saunders said.

"We know from studies of the general population that women have a different type of sleep architecture than men, and they're at different risks for sleep disorders, particularly during the reproductive years," Saunders said.

The researchers analyzed data from 216 participants. They looked at the effect of sleep quality at the beginning of the study on mood outcome over the next two years.

Mood outcome was measured by the severity, frequency and variability of depressive or manic symptoms. For women, poor sleep quality predicted increased severity and frequency of depression and increased severity and variability of mania.

Among men, baseline depression score and a personality trait called neuroticism were stronger predictors of mood outcome than sleep quality.

"We feel it's extremely important for clinicians and patients to recognize that sleep quality is an important factor that needs to be treated in patients with bipolar disorder, particularly in women," Saunders said.

The research was published in the Journal of Affective Disorders.