Evidence-Based Reviews

Unipolar vs bipolar depression: A clinician’s perspective

Gary E. Miller, MD
Clinical Professor of Psychiatry

Richard L. Noel, MD
Assistant Clinical Professor of Psychiatry
• • • •
McGovern Medical School at UTHealth
The University of Texas Health Science Center at Houston
Houston, Texas

The authors report no financial relationships with any companies whose products are mentioned in this article or with manufacturers of competing products.

A careful assessment of select criteria can help make the distinction.



Mrs. W, age 36, who is married, has a history of military service, and is currently employed as a paralegal, is referred to our practice by her family physician. She complains of severe depression that impairs her ability to function at work. She had seen several other psychiatrists in both military and civilian settings, and had been treated with multiple antidepressants, including fluoxetine, sertraline, bupropion, and paroxetine.

At the time of her initial psychiatric evaluation, she is taking duloxetine, 90 mg/d, but still is experiencing depressive symptoms. She is tearful, sad, lacks energy, spends too much time in bed, and is experiencing thoughts of hopelessness, despair, and escape, verging on thoughts of suicide. As a result, she needs to scale back her work schedule to part-time. When asked about how long she had been suffering from depression, she responds “I’ve been depressed all my life.” She had been briefly hospitalized at age 16, when she made a suicide attempt by overdose. There had been no subsequent suicide attempts or psychiatric hospitalizations, although she acknowledges having intermittent suicidal thoughts.

Mrs. W’s clinical presentation is similar to that of many patients entering our practice—patients who have recurrent depression that began in early life and a history of failure to respond to multiple antidepressants. She and other patients with similar presentations are not suffering from treatment-resistant depression and in need of a trial of electroconvulsive therapy, transcranial magnetic stimulation, direct current stimulation, vagus nerve stimulation, or intranasal esketamine. She has bipolar disorder, and had been repeatedly misdiagnosed and treated inappropriately with antidepressant monotherapy.

In a previous article1 (“Controversies in bipolar disorder: Trust evidence or experience?,” Current Psychiatry, February 2009, p. 27-28,31-33,39), we endorsed the concept of a bipolar spectrum. We also argued that subthreshold hypomania is the rule and not the exception in bipolar II disorder, that antidepressant monotherapy rarely causes manic switches but is more likely to worsen depression, and that although antidepressant monotherapy usually destabilizes bipolar illness, antidepressants can be helpful when combined with mood stabilizers. We observed that bipolar disorder occurs frequently in children and adolescents and that psychosis is a common occurrence in patients with bipolar disorder. We also outlined what we consider to be the major clinical features of bipolar depression and noted the role of thyroid hormones in managing mood disorders.

In this article, based on our more than 25 years of experience in diagnosing and treating psychiatric disorders in patients of all ages, we expand on those observations.

Misdiagnosis is common

Bipolar depression is frequently misdiagnosed as unipolar depression in outpatient2-8 and inpatient9 settings, and in children and adolescents.10 Mrs. W is typical of patients who have what we consider a bipolar spectrum disorder and receive an inaccurate diagnosis and treatment that is ineffective or may worsen the course of their illness.

Reliance on DSM-511 and its predecessor, DSM-IV, is a part of the problem of misdiagnosis because the diagnostic criteria for bipolar disorder fail to capture the clinical features of many patients with “softer” (less obvious manic and hypomanic) variants of the disorder.12,13 For example, DSM-5 criteria for a hypomanic episode (the mild high experienced by patients with a soft bipolar disorder) require that the episode lasts “at least 4 consecutive days” and is “present most of the day, nearly every day.” In our experience, the majority of hypomanic episodes are shorter—ranging from a half-day to 2 days, averaging perhaps 1.5 days.

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