Major depressive disorder (MDD) is often difficult to differentiate from depression present in persons with Bipolar Disorder (BD).This is because the symptoms in the depressive phase of bipolar disorder are the same with those of major depression.However, the treatment for either disease is different and if misdiagnosed, the situation could end up getting worse.

Bipolar disorder

Take the case of bipolar disorder, formerly known as manic depression.Patients suffering from it will swing between an emotional high -- more of a manic episode -- and severe depression.For the depression phase, a patient is administered with an antidepressant and a safeguard such as a mood stabilizer or even an antipsychotic drug to prevent the patient from switching to a manic episode.Now if any physician were to misdiagnose bipolar disorder as major depression, he/she would prescribe the patient an antidepressant without a safeguard mood-stabilizing drug, putting the patient at risk of having his/her manic episode triggered.

Cases of misdiagnosis are a lot and the fact that major depression is one of the most common and severe health problems in the world does not help.Depression occurs in people of all ages across the world.It is the leading cause of disability and its global burden has increased by over 35 percent between 1990 and 2010.In fact, in the United States alone, at least 8 to 10 percent of the population is suffering from major depression at any given time.Bipolar disorder is much less common than major depression, but it's a significant mental health problem with an estimated 50 million people suffering from the disorder worldwide.

A groundbreaking study by the Department of Health from Loyola University has pointed that a simple electrocardiogram running for approximately 15 minutes could help a physician determine whether a patient has major depression or bipolar disorder.The study was conducted by  Angelos Halaris, MD, Ph.D., and his colleagues and was published in the World Journal of Biological Psychiatry.

Dr.Halaris is a professor in the Loyola University Department of Psychiatry and Behavioral Neurosciences and medical director of adult psychiatry.He said, "Having a non-invasive, 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." He later added that further research was needed to confirm the study findings and determine their clinical significance.

During the study, Dr.Halaris and his Loyola colleagues enrolled 64 adults diagnosed with major depression and 37 adults suffering from bipolar disorder.All the participants underwent an electrocardiogram at the start of the study.Each of them was rested comfortably on an exam table, and three lead electrocardiogram devices were attached to the chest.The patients were then rested for 15 minutes, and the electrocardiographic data were collected for 15 minutes.

The researchers then used a special software package and converted the electrocardiographic data into the components of heart rate variability.The study's co-author Stephen W.Porges of Indiana State University's Kinsey Institute developed specialized software programs to further the correctness of the data.

Autonomic Nervous System (ANS) dysregulation is usually considered a pointer to various depressive symptoms and inflammatory response disinhibition.The beat-to-beat pattern of the heart rate which is essentially the heart rate variability can offer a non-invasive portal to the Autonomic Nervous System function and provides a resting cardiac vagal tone.Autonomic changes are usually found in altered mood states and are considered to be a central biological substrate which links depression to a number of physical dysfunctions.Any defections in the autonomic nervous system functioning that promotes vagal withdrawal reflected in reductions of heart rate variability indexes.Reduction in the heart rate variability is an indication of emotional dysregulation, decreased psychological flexibility and defective social engagement.All these symptoms are linked to prefrontal cortex hyperactivity.

Major Depressive Disorder

The researchers quantified the heart rate variability and measured inflammatory biomarkers in Major Depressive Disorder and Bipolar Disorder in an attempt to derive potential diagnostic criteria for both disorders.

In quantifying the heart rate variability, the researchers were able to compute what is known in the cardiology world as Respiratory Sinus Arrhythmia (RSA).At the beginning of the study, the patients with major depression had a significantly higher respiratory sinus arrhythmia than those with bipolar disorder.

In the case of inflammatory biomarkers, the researchers found out that patients with bipolar disorder had higher blood levels of inflammation biomarkers than patients suffering from major depressive disorder.The inflammation occurs when the immune system preps up in response to a stressful condition such as bipolar disorder.

The study was successful in showing that a reduced vagal tone and higher levels of inflammatory biomarkers may be a perfect way for physicians to distinguish persons suffering from bipolar disorder and major depressive disorder.At the same time, the findings may reveal an underlying pathophysiology of depression involving an autonomic nervous system and chronic immune system dysregulation.