A disrupted sleep-wake cycle is not only a symptom but also a contributing
factor in mood disorders, according to three studies published in the December
2008 American Journal of Psychiatry (AJP).
In a study conducted by Hyong Jin Cho, M.D., Ph.D., and colleagues,
clinically significant sleep disturbance was found to be an independent
predictor for a recurrent depressive episode within two years in
community-dwelling adults aged 60 or older after controlling for other
potential confounding factors such as medication use and other chronic
Sleep disturbance was defined in this study as a score above 5 on the
Pittsburgh Sleep Quality Index.
Although the 145 study participants with a history of depression were in
full remission at baseline, sleep disturbance was more common in these
subjects (46 percent) than among the 206 control subjects who had no history
of depression at baseline (18 percent). In the two-year follow-up, 17 percent
of those with a depression history developed recurrent depressive episodes,
significantly higher than the incidence of depression (0.5 percent) in those
without the history.
Plasma melatonin concentrations showed abnormal patterns in women with
depression during and after pregnancy, according to another study published in
the same issue by Barbara Parry, M.D., and colleagues. Compared with
nondepressed pregnant women (n=15) matched for weeks into pregnancy, the
pregnant women with major depression (n=10) had significantly lower levels of
melatonin from 2 a.m. to 11 a.m. In contrast, women with postpartum depression
(n=13) had significantly higher melatonin levels than nondepressed postpartum
women (n=11) across all time intervals.
Melatonin is a hormone synthesized from serotonin in the pineal gland and
is known to play an important role in regulating the sleep-wake cycle. Plasma
level of melatonin is an indicator of the circadian rhythm. It rises
approximately two hours before sleep and decreases during early morning
The same group of authors previously reported study results showing
decreased and earlier-shifted melatonin rhythms in women with cyclic mood
disturbance before menstruation and higher melatonin levels in women with
In the third study, Ellen Frank, Ph.D., and colleagues found that bipolar
patients randomly assigned to interpersonal and social rhythm therapy (n=61)
improved their work functioning significantly faster than patients assigned to
intensive clinical management (n=64). At the end of two years of the trial,
however, the level of work functioning improved to virtually the same level
regardless of the treatment approach.
Interpersonal and social rhythm therapy is a manual-based treatment
designed to help patients "stabilize their daily routines and sleep-wake
cycles in the hopes of stabilizing endogenous circadian rhythms" and"
resolve interpersonal problems related to grief, role transitions, role
disputes, and interpersonal deficits," the authors explained. Intensive
clinical management involved more conventional medical management of bipolar
disorder including patient education, nonspecific support, and management of
medications and side effects.
The challenge for researchers is to separate the cause and effect between
the pathophysiology of mood disorders and disruption of circadian and sleep
rhythms as well as to elucidate how mood and sleep interact with each other,
Ellen Leibenluft, M.D., chief of the Section on Bipolar Spectrum Disorders in
the Emotion and Development Branch, Mood, and Anxiety Program at the National
Institute of Mental Health, commented in an editorial in the same issue. For
example, it is difficult to determine which is the cause and which the effect
between abnormal melatonin plasma levels and depression in pregnant and
Clinical evidence has shown that sleep deprivation has some antidepressant
effect and often precedes a manic episode in certain bipolar patients.
Studies of sleep-wake and circadian rhythm disturbance in people with mood
disorders "have the potential to suggest novel therapeutic approaches,
both pharmacological and nonpharmacological," Leibenluft wrote.
Considering the significant adverse effects of chemical sleep aids, she
recommended that clinical studies on "nonpharmacological interventions
for the treatment of insomnia should receive serious consideration."
The editorial, "The Rhythm of the Blues," and the three
studies, "Sleep Disturbance and Depression Recurrence in
Community-Dwelling Older Adults: A Prospective Study," "Plasma
Melatonin Circadian Rhythm Disturbances During Pregnancy and Postpartum in
Depressed Women and Women With Personal or Family Histories of
Depression," and "The Role of Interpersonal and Social Rhythm
Therapy in Improving Occupational Functioning in Patients With Bipolar I
Disorder," are posted at<http://ajp.psychiatryonline.org/content/vol165/issue12/index.dtl>.▪