Authors: Francis Davies
The study, published in the World Journal of Biological Psychiatry, revealed that heart rate variability can be indicative of crucial differences when diagnosing major depressive disorder or bipolar disorder in a patient.
Easy to misdiagnose, bipolar disorder shares symptomatic similarities with major depression, though the two illnesses represent different and often challenging treatments for a physician. A misdiagnosis of major depression in a patient with bipolar disorder may inadvertently cause manic episodes if the physician prescribes an antidepressant without a safeguard mood-stabilizing drug.
Autonomic nervous system (ANS) dysregulation has previously been associated with several depressive symptoms and inflammatory response disinhibition. Evaluating heart rate variability (HRV) therefore allowed the researchers insight into ANS function, providing a record of relaxed cardiac vagal tone.
The study at Loyola University ( IL, USA) enrolled 64 adults with major depression and 37 with bipolar disorder. Prior to beginning, participants underwent antidepressant washout and blood was drawn at baseline. After a 15 minute period of rest, while a three-lead electrocardiogram was attached to their chests, researchers collected the electrocardiographic data for a further quarter of an hour.
The electrocardiographic data was converted into the components of HRV and measured respiratory sinus arrhythmia (RSA). At the baseline, subjects with major depression displayed a significantly higher RSA than those with bipolar disorder. A secondary finding revealed that patients with bipolar disorder had higher blood levels of inflammation biomarkers than those with major depression.
Angelos Halaris (Loyola University Medical Center) stressed a necessity for further study into the pathophysiology of depression to determine the clinical significance of the study, but commented: “Having a noninvasive, easy-to-use and affordable test to differentiate between major depression and bipolar disorder would be a major breakthrough in both psychiatric and primary care practices.”
Sources: Hage B, Britton B, Daniels D, Heilman K, Porges SW, Halaris A. Low cardiac vagal tone index by heart rate variability differentiates bipolar from major depression. World J. Biol. Psychiatry https://doi.org/10.1080/15622975.2017.1376113 (2017) (Epub ahead of print); www.eurekalert.org/pub_releases/2017-11/luhs-sec112017.php