Still in the Dark: Unknown Relationship Between Bipolar Disorder and Circadian Cycles

Better understanding the relationship between bipolar disorder (BD) and circadian cycles can help establish new treatment protocols and treatment modalities, according to a review in the Journal of Affective Disorders.

The review is not the first to suggest a strong connection between the sleep/wake cycle and BD. For at least 70 years, clinical investigators have questioned whether abnormalities in circadian rhythm regulation might be involved in the pathogenesis of mood disorders, including BD. The genesis of this area of research was clinical observations, including the fact that the sleep duration of patients often changes dramatically as they cycle between mania and depression, and a curious finding that more than half of depressed patients experience remission after a night of total or partial sleep deprivation. Other early studies concluded that even if circadian abnormalities are not the primary cause of bipolar illness, it is possible that circadian interventions can have therapeutic utility.

The authors of the recent analysis noted that abnormal circadian rhythms are ubiquitous in BD, even during the balanced (euthymic) phase, with altered melatonin, cortisol, body temperature, and locomotor activity cycles. Strong clinical evidence, however, showing the effectiveness of circadian interventions is currently sparse. The review looked at all recent studies using a keyword search of terms such as: bipolar, circadian, melatonin, cortisol, Clock gene, light therapy, dark therapy, and sleep deprivation, among others.

In particular, the review focused on chronotherapy, which has been used to treat other mood disorders, asthma, cancer, cardiovascular disease, and hypertension, among other conditions, and found some evidence of demonstrated efficacy in BD treatment. In addition, the team looked at the slim, sometimes conflicting clinical results of such therapy options as lithium carbonate, agomelatine, light therapy, dark therapy, sleep deprivation and interpersonal and social rhythm therapy.

A large clinical trial led by researchers at Norway’s University of Bergen, for example, hypothesized that virtual darkness therapy is effective as additive treatment in mania. But although the study was completed earlier in 2015, results have not yet been shared.

“In the future, it is essential to achieve a better understanding of the relation[ship] between bipolar disorder and the circadian system,” the review authors concluded.