Minor Depression: Midway between Major Depression and Euthymia

When it comes to mood disorders, major depression has dominated the headlines. Diagnosis of major depression requires that the patient have at least 5 of 9 criterion symptoms (1 of which must be depressed mood or anhedonia) nearly every day for 2 or more weeks. Attracting somewhat less attention, dysthymia is a chronic disorder that manifests as depressive symptoms that persist more days than not for several years. Diagnosis of dysthymia does not require at least 5 symptoms, unlike major depression. Minor depression has been the Cinderella of the 3 conditions: The diagnosis requires neither meeting the symptom threshold of major depression nor the chronicity threshold of dysthymia. Mood disorder research has corresponded to this rank ordering. Therefore, clinicians have a rather robust evidence-based approach to the management of major depression, a more modest understanding of what to do for the patient with dysthymia, and even fewer data to guide them in caring for the patient with minor depression.

The lack of consensus on how to define minor depression has slowed the progress of research (1, 2). The most common names are minor, subthreshold, and subsyndromal depression. The American Psychiatric Association criteria for minor depression are the presence of 2 to 4 of the 9 core symptoms of depressive disorders (Table) nearly every day for at least 2 weeks to a degree that causes clinically significant distress or impairment in one's usual activities or social relationships (3). As with any depressive disorder, at least 1 of the patient's symptoms must be depressed mood or anhedonia.

Because studies of minor depression vary in their requirements for symptom count, duration, and impairment, it is difficult to directly compare or combine study results. Despite this heterogeneity, 3 themes consistently emerge. First, minor depression is at least as prevalent as …