Duration of Periods of Euthymia in Patients With Dysthymic Disorder

This article discusses the duration of euthymic periods in individuals diagnosed with dysthymic disorder. Dysthymic disorder, as defined in DSM-IV, is a form of chronic depression that is characterized by a depressed mood more days than not, with a grouping of symptoms that lasts 2 years or more in adults and 1 year or more in children.

The criterion that symptoms of depression be present “more days than not” suggests that patients need to be depressed at least 50% of the time and that their mood alternates from depressed to euthymic in some form of sporadic pattern. Inherent in the DSM-IV criteria for dysthymic disorder are periods of euthymia that last no longer than 2 months. A second pattern of depressive symptoms in dysthymic disorder is possible, one that has chronic symptoms every day that last 2 years or longer but without sufficient depressive symptoms to meet the criteria for a major depressive episode—i.e., a patient who has a daily depressed mood and up to three of the symptoms from the list of items for major depressive episode. Such patients would not necessarily experience euthymia but could meet the criteria for dysthymic disorder. About 15% of the patients with dysthymia show this pattern.

Considering that the criteria in DSM-IV allow for up to 2-month-long periods of euthymia, I asked a consecutive series of patients who met the criteria for dysthymic disorder to recall the duration of their euthymic periods in order to clarify the duration of euthymic episodes that characterizes patients with this disorder. To my knowledge, the selection of a 2-month period as a criterion was not on the basis of data but is consistent with the 2-month requirement for an interval between major depressive episodes that determines that such episodes are recurrent.

METHOD

All patients who came for treatment at the Center for Anxiety and Depression from Jan. 1, 1998, to Oct. 31, 1998, were interviewed by the author by using a semi-structured interview (1). All patients who met the DSM-IV criteria for dysthymic disorder were included in the present study. All patients gave written informed consent for participation in the study, which included a review of their records.

Patients who met the DSM-IV criteria for dysthymic disorder (N=22) were asked to recall their longest period of euthymia during untreated periods. Other data obtained included the 17-item Hamilton Rating Scale for Depression score (2), the Hamilton Rating Scale for Anxiety score (3), the Global Assessment of Functioning Scale score, history of treatment, and history of other psychiatric illnesses including major depressive disorder. To be included, patients needed to meet the DSM-IV criteria for a dysthymic disorder that was uncomplicated by another axis I condition for the 2 years before the interview. Subjects who did not meet the criteria for another psychiatric disorder were described as having primary uncomplicated dysthymic disorder. Subjects who experienced another axis I disorder that resolved itself were described as having secondary dysthymic disorder. Subjects who first experienced dysthymic disorder and who then had another axis I condition that subsequently remitted were described as having primary complicated dysthymic disorder. I also was interested in discovering if the duration of the euthymic periods differed if patients were primary uncomplicated or not. Statistical analyses were performed with the SPSS 8.0 software package.

RESULTS

Twenty-two patients were assessed over the index period. Of these, 12 had primary uncomplicated dysthymia, six had secondary dysthymic disorder, and four had a history of primary but complicated dysthymic disorder. Fourteen patients were men. The mean age of the 22 patients was 42.3 years (SD=13.8). Their mean Hamilton depression scale score was 17.4 (SD=2.3).

The duration of periods of euthymia in these individuals varied from 2 to 30 days, and the mean duration of periods of euthymia was 8.0 days (SD=6.6). No patient in this study described a euthymic period of longer than 1 month. None of the patients had chronic (daily) symptoms. Seventy-three percent (N=16) of the patients described 7 days or fewer of euthymia, and 95% (N=21) described 14 days or fewer of euthymia.

I found no significant differences between patients with primary uncomplicated dysthymia and patients with other dysthymia in means for age, age at onset of illness, duration of euthymia, Hamilton anxiety scale score, Hamilton depression scale score, or percentage of time depressed. The mean Global Assessment of Functioning Scale score was significantly lower for subjects with primary uncomplicated dysthmia (mean=53.6, SD=7.1) than other dysthymic patients (mean=61.7, SD=8.3) (t=–2.33, df=20, p<0.05).

DISCUSSION

In my study, dysthymic patients recalled a mean of 8.0 days’ duration of euthymic periods with a range of 2 to 30 days. Slightly over 70% (N=16) of the patients described 1 week or less of euthymia. I view these data as relevant to considerations of the definition of dysthymic disorder for DSM-V. However, it should be noted that this information was obtained by one investigator asking patients to recall euthymic periods at a point in their lives when they had been ill for a mean of almost 8 years. The reliability of these data was not assessed. It is possible that a different study design using daily mood calendars might result in a more accurate mean length and range of euthymic periods. However, given the fact that patients with dysthymic disorder are relatively infrequently seen in psychiatric settings, it is unlikely that a prospective study of this design could be easily applied to untreated patients.

The duration of euthymic periods has important implications for the design of placebo-controlled treatment studies of dysthymic patients. If a relatively long period of euthymia is consistent with the untreated course of the illness, then dysthymic subjects who participate in treatment studies are likely to show a high response rate to a placebo. On the other hand, dysthymic disorder is frequently complicated by major depressive episodes, which results in so-called “double depression” (4). Thus, there is the possibility of worsening depression during treatment trials.

My group (5) has also suggested that dysthymic disorder, a diagnosis created in 1980 with DSM-III and perpetuated through DSM-IV, might be an artificial subdivision of mood disorders. There are many similarities of patients with dysthymic disorder to other forms of chronic depression, particularly chronic major depressive disorder. The items used to diagnose a depressive episode are quite applicable to diagnosing dysthymic disorder (6). Pages and Dunner have proposed a classification for DSM-V mood disorders that divides patients with depression into recurrent or chronic groups, with the chronic depressive category including what DSM-IV terms “chronic major depressive disorder” and “dysthymic disorder” and the recurrent depressive category including “bipolar II disorder” and “recurrent unipolar disorder” (5). Data supporting this notion would be of interest.

Received Jan. 11, 1999; revision received April 20, 1999; accepted June 3, 1999. From the Department of Psychiatry and Behavioral Sciences, Center for Anxiety and Depression, the University of Washington. Address reprint requests to Dr. Dunner, Center for Anxiety and Depression, 4225 Roosevelt Way NE, Suite 306C, Seattle, WA 98105-6099; [email protected] (e-mail)