More Research Needed on Connection Between Circadian Rhythms, Bipolar Disorder

MJ McCarthy, MD

A look at current literature in the association between circadian rhythm disruption and bipolar disorder (BD) has shown the need for more insight and research in this field.

A team, led by MJ McCarthy, MD, UC San Diego, Department of Psychiatry & Center for Circadian Biology, reviewed evidence for neurobiological and behavioral mechanisms related to bipolar disorder.

Bipolar Disorder

Patients with bipolar disorder often have symptoms regulated by circadian function, including changes in mood, activity, energy, sleep, and appetite. In the past, circadian rhythm disturbances have been studied as a biological featured underlying bipolar disorder.

In the study, which was commissioned by the International Society for Bipolar Disorders (ISBD) Chronobiology Task Force (CTF), the investigators analyzed relevant cross-disciplinary literature to identify exactly how circadian rhythm disruption impacts patients with bipolar disorder. This represents the first time researchers have integrated findings across levels of analysis to create an internally consistent and coherent theoretical framework.

Circadian System

The findings show the circadian system has a role in mood regulations that are associated with a bipolar diagnosis and mood-related traits across genetic, cellular, physiological, and behavioral domains.

However, circadian disruption is not specific in bipolar disorder and presents across a variety of high-risk, prodromal, and syndromic psychiatric disorders. There was significant variability and ambiguity among the different definitions, concepts, and assumptions underlying the current research with limited replication and the emergence of consensus findings.

“Future research in circadian rhythms and its role in BD is warranted,” the authors wrote. “Well-powered studies that carefully define associations between BD-related and chronobiologically-related constructs, and integrate across levels of analysis will be most illuminating.”

Sleep And Psychiatric Disorders

Other conditions have been long associated with sleep disturbances. For example, earlier this year researchers provided better insight into why patients with attention deficit/hyperactivity disorder (ADHD) suffer from greater rates of sleep issues, including insomnia and excessive sleepiness.

Impaired sleep is a known risk factor for several negative health outcomes, such as deficits in executive function, attention, and impulse control, which all happen to be symptoms of ADHD. About half of ADHD patients report sleep disturbances, with delayed sleep onset being the most commonly reported symptom.

Sleep deprivation is also linked to reduced dorsolateral prefrontal activity, as well as difficulty regulating attentional resources. This could help explain the inability to attend to a stimulus in the presence of distractions or engage in goal-directed behavior.

Overall, the patients with ADHD reported greater impairment on sleep quality (P = 0.009), insomnia (P = 0.004), and sleepiness (P = 0.029).

The patients with higher sleep quality scores also had lower SHAPS scores, regardless of ADHD diagnosis (β = -0.235; P = 0.012).

The association of ADHD diagnosis and sleepiness scores was influenced by SHAPS scores (b = 0.199, P = 0.039), to where the significance of the relationships increased with higher SHAPS scores.

The study, “Neurobiological and behavioral mechanisms of circadian rhythm disruption in bipolar disorder: A critical multi-disciplinary literature review and agenda for future research from the ISBD task force on chronobiology,” was published online in Bipolar Disorders.