Evidence-Based Reviews

Unipolar vs bipolar depression: A clinician’s perspective

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Genetics. Bipolar disorder is one of the most heritable of illnesses.32 Family history is important, but affected relatives may have been misdiagnosed with unipolar depression or schizophrenia, or said to have experienced “nervous breakdowns.”

Consequences of misdiagnosis

Misdiagnosis of patients with bipolar disorder is not benign. We see patients who have suffered needlessly for years with severe depression and mood instability. After trying antidepressant after antidepressant without benefit, they begin to feel hopeless, believing they have tried everything and that nothing works for them. Often, these patients have dropped out of high school or college, or lost jobs, friends, and spouses due to their disabling but misdiagnosed psychiatric disorder. Patients with misdiagnosed bipolar disorder have an increased risk of suicide attempts and psychiatric hospitalization.5,8

Misdiagnosis of patients with bipolar disorder is not limited to nonpsychiatric physicians. The majority of patients with bipolar spectrum disorders are misdiagnosed by outpatient psychiatrists as having unipolar depression.2-7 At least 45% of patients hospitalized for depression have bipolar disorder—and most of these patients are treated inappropriately with antidepressants.9 The STAR*D study,33,34 a large randomized clinical trial of antidepressants, concluded that more than one-third of patients had not remitted from their depression after treatment with 3 different antidepressants. In our opinion, many of the nonresponding patients may have undiagnosed bipolar depression, which predictably leads to a failure to respond adequately to antidepressants. We believe that the customary inclusion and exclusion criteria used to select participants for these research studies miss subtle (subthreshold) hypomanic episodes that fall short of meeting DSM criteria for duration and severity. This phenomenon may account for the results of studies that conclude that antidepressants are, at best, minimally more effective than placebo.35

When a patient with a bipolar spectrum disorder is misdiagnosed and treated with an antidepressant, the usual result is mood destabilization. Reports of mood swings, increased crying, and suicidal thoughts and suicidal gestures in children, adolescents, and young adults treated with antidepressants led the FDA to issue a “black-box” warning.36 Because bipolar depression typically begins in youth,10,18,19 the behaviors cited in the warning may reflect misdiagnosis of bipolar depression as unipolar depression, and consequent mood destabilization as a result of treatment with an antidepressant in the absence of a mood stabilizer.

Depression and life stressors

Since many patients who are depressed present with a history of significant stressors, clinicians often face the problem of distinguishing between clinical depression and stress-induced depression. We believe that one typical symptom of depression—increased sensitivity to stressors—may help in making that distinction. A patient who is depressed will often attribute depression to stressors such as marital conflict, divorce, problems with a teenage child, work pressures, financial pressures, or the illness or death of a family member or pet. If clinical depression (unipolar or bipolar) is present, the symptoms are persistent, sometimes antedate the stressor by days or weeks, often outlast the stressor, increase in severity over time, and are disproportional to the stressor. Clinical depression can also cause the patient to become obsessed with traumatic events or losses that occurred many years earlier.

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