Major depressive disorder and dysthymic disorder, commonly known as dysthymia, represent two mood disorders classified by the "Diagnostic and Statistical Manual" of the American Psychiatric Association. Both disorders are characterized by feelings of sadness or apathy, but have distinctly different time duration and symptom patterns that must be carefully assessed for an accurate diagnosis.
According to the National Institute of Mental Health, major depressive disorder afflicts approximately 14.8 million American adults, or 6.7 percent, in a given year. Dysthymia annually affects approximately 3.3 million American adults, or 1.5 percent of the U.S. adult population. The median age of onset for both diagnoses occurs in the early 30s.
Both major depressive disorder and dysthymia are mood disorders that manifest as depressed or sad mood. To be diagnosed, several other symptoms also need to occur for a certain minimum length of time. The specific diagnostic criteria for the number of symptoms, intensity and duration differ for the two disorders.
Number of Symptoms
For a diagnosis of major depressive disorder, an individual must experience at least five out of nine characteristic symptoms over at least a two week period. One of these symptoms must be either depressed mood or loss of interest or pleasure in activities normally enjoyed. Other characteristic symptoms can include significant changes in appetite and weight, sleeping less or more than usual, physical agitation or slowness, fatigue, feelings of worthlessness, inability to concentrate, and recurrent thoughts of death or suicide, according to the American Psychiatric Association.
Dysthymia requires fewer symptoms for diagnosis. The individual must have the depressed mood and at least two other symptoms from a list of six, which may include appetite changes, sleep difficulties, fatigue, low self-esteem, poor concentration and feelings of hopelessness.
Duration and Intensity of Symptoms
For a diagnosis of major depressive disorder, a person must experience at least one major depressive "episode," characterized by at least two weeks of depressive symptoms, according to the American Psychiatric Association. Symptoms must occur most of the day, nearly every day of that two week period.
Dysthymia symptoms must occur over a longer period of time, but are of lesser intensity, than major depressive disorder. Dysthymia presents as chronic depression that must last for at least two years to be diagnosed. The depressed mood must only be present, according to the American Psychiatric Association, "more days than not," compared to "nearly every day" for major depressive disorder. To qualify for a diagnosis of dysthymia, an individual cannot be free of the depressed mood for more than two continuous months of that two-year period.
Depression and Dysthymia in Children
In children, obvious signs of a low, sad or depressed mood may not occur, as children's emotional patterns differ from those of adults. Instead, chronic and unremitting irritability may characterize the child with depression or dysthymia, according to the American Psychiatric Association.
For a diagnosis of dysthymia in children, the symptoms need only occur for one year. Again, the symptoms cannot remit for more than a two-month period.
People with dysthymia can experience bouts of major depression. When this occurs, it is colloquially known as double depression. For this designation, dysthymia needs to have occurred for at least two years in the lifetime of the individual before full-fledged symptoms of a major depressive episode occurs. Double depression is not a formal diagnosis in the "Diagnostic and Statistical Manual" of the American Psychatric Association, but is often used informally by clinicians.