by Randy A. Sansone, MD, and Lori A. Sansone, MD
Dr. R. Sansone is a professor in the Departments of Psychiatry and Internal Medicine at Wright State University School of Medicine in Dayton, Ohio, and Director of Psychiatry Education at Kettering Medical Center in Kettering, Ohio; Dr. L. Sansone is a family medicine physician (government service) and Medical Director of the Primary Care Clinic at Wright-Patterson Air Force Base. The views and opinions expressed in this column are those of the authors and do not reflect the official policy or the position of the United States Air Force, Department of Defense, or US government.

Psychiatry (Edgemont) 2009;6(11):14–17

Financial Disclosures

The authors have no conflicts of interest relevant to the content of this article.

ABSTRACT

In the current Diagnostic and Statistical Manual of Mental Disorders, dysthymic disorder is categorized as either early-onset or late-onset, based upon the emergence of symptoms before or after the age of 21, respectively. Does this diagnostic distinction have any meaningful clinical implications? In this edition of The Interface, we present empirical studies that have, within a single study, compared individuals with early- versus late-onset dysthymia. In this review, we found that, compared to those with late-onset dysthymia, early-onset patients are more likely to harbor psychiatric comorbidity both on Axis I and II, exhibit less psychological resilience, and have more prominent family loadings for mood disorders. These findings suggest that this distinction is meaningful and that the early-onset subtype of dysthymia is more difficult to effectively treat.

Key words

dysthymia, dysthymic disorder, depression, depression subtypes

INTRODUCTION

The word dysthymia is derived from the Greek language and translates as, “bad state of mind,” “ill humor,” or “abnormal feelings.” Dysthymic disorder, the likely result of a compilation of various types of chronic mood disturbances, first officially debuted in the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM) in 1980.[1] However, it was not until the next version of the DSM in 1987 (the revised third edition) that dysthymic disorder was subclassified into early- versus late-onset.[2] These two distinctions refer to symptom presentation before (early onset) versus after (late onset) the age of 21 years. According to the available research, this distinction in onset appears to be scientifically viable and has a number of clinical implications. In this edition of The Interface, we examine the available empirical studies that, within the same study, compared individuals with early-onset versus late-onset dysthymia and discuss findings.

The Clinical Definition of Dysthymia

In the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR),[3] dysthymic disorder is described as a semichronic, smoldering mood disorder with ongoing waxing and waning symptoms. Symptoms must be present for at least two years in adults and for at least one year in children and adolescents. The affected individual must have at least two of the following mood-related symptoms: (1) change in appetite (i.e., increase or decrease), (2) change in sleep pattern (i.e., increase or decrease), (3) fatigue or low energy, (4) low self-esteem, (5) decrease in concentration or indecisiveness, and (6) feelings of hopelessness. While brief periods of normal mood may punctuate the course, symptoms during this two-year period are never absent for more than two consecutive months. At the outset, there is no history of major depression, although after onset, a substantial number of patients experience superimposed episodes of acute depression.

Early- versus Late-Onset Dysthymia: The Clinical Differences

In the existing literature on dysthymia, there are a number of studies that have compared patients with dysthymia to those with major depression. In these studies, the majority of patients with dysthymia are reported to suffer from the early-onset subtype. However, far fewer studies have undertaken direct comparisons of patients with early-onset versus late-onset dysthymia within the same study. While the following review may not be fully complete, we believe that it provides evidence that this subclassification of dysthymia is clinically useful. We will present these studies in chronological order, beginning with the earliest publication in this area that we could locate.

In 1988, Klein et al[4] examined the validity of the early versus late-onset distinction by comparing the two on a number of different clinical variables. At the conclusion of the study, researchers found that, compared with late-onset dysthymics, those with early-onset dysthymia evidenced a greater number of major depressive episodes (a common comorbidity in patients with dysthymia), a greater number of anxiety disorders, more treatment-seeking, a greater rate of major affective disorders in first-degree relatives, and greater levels of depression during a six-month follow-up period.

In 1990, McCullough et al[5] compared early- versus late-onset dysthymics with regard to onset patterns, cognitive styles, coping strategies, and symptom measures. While the two groups were similar in many ways, they displayed some differences in coping style. Explicitly, patients with early-onset dysthymia were significantly more likely to use (1) stress as an impetus for growth and (2) emotion-focused coping rather than problem-solving coping.

In a Hungarian sample, Szadoczky et al[6] examined epidemiological and neurohormonal differences between these two subgroups of dysthymics. In this 1994 study, all participants also had comorbid major depression. In examining between-group differences, the researchers found that early-onset dysthymics were more likely to be unmarried, report childhood adversity, evidence nonsuppression on the dexamethasone suppression test, and have blunted thyroid stimulating hormone responses after thyrotropin-releasing hormone administration.

In a 1996 Canadian study, Ravindran et al[7] examined onset differences in dysthymia with regard to life stressors and coping styles. Compared with late-onset participants, those with early-onset dysthymia were less resilient in dealing with life stressors and evidenced a greater degree of emotion-based coping strategies.

In a Brasilian sample, Versiani, Amrein, and Stabl[8] examined antidepressant responses as a function of symptom onset in dysthymia. In this endeavor, the study medications were moclobemide (a reverse inhibitor of monoamine oxidase, with adjunctive effects on norepinephrine, serotonin, and dopamine) and imipramine. In examining symptom response to these medications according to the Hamilton Rating Scale for Depression, moclobemide was significantly more effective in the early-onset group, compared to imipramine.

In a 1999 study in the UK, Garyfallos et al[9] examined the prevalence of comorbid personality disorders in a sample of patients with dysthymia. These investigators encountered a number of comorbid Axis II disorders including borderline, histrionic, avoidant, dependent, and self-defeating personality disorders, which were over-represented in participants with the early-onset subtype.

In another 1999 study, Klein et al[10] examined 340 outpatients with dysthymia. In this large sample, 73 percent were classified as early-onset whereas 27 percent were classified as late-onset. Compared with late-onset participants, those with early-onset dysthymia were more likely to suffer from longer episodes of comorbid major depression, comorbid personality disorders, and a greater lifetime prevalence of substance use disorders. Participants in the early-onset subsample also had more frequent family histories of mood disorders. In this study, there were no between-group differences with regard to symptom severity or functional impairment.

Barzega et al[11] examined an Italian sample of 84 consecutive outpatients with dysthymia. Contrary to the preceding sample of Klein et al,[10] only 23 percent of participants in this 2001 study had early-onset dysthymia. Compared to those with late-onset symptoms, those with early-onset dysthymia were more likely to be younger, female, and single; report a longer duration of illness and a greater rate of consultation for treatment; and evidence a history of major depression. The early-onset subsample also evidenced a greater number of specific Axis I disorders, including social phobia and panic disorder. There were no between-group differences in terms of symptom frequency.

Devanand et al[12] examined elderly patients with dysthymia with comorbid major depression. In this 2004 study, late-onset patients were more likely to suffer from cardiovascular disease. In contrast, anxiety disorders were more prevalent in participants with early-onset dysthymia.

Finally, in an Italian study from 2006, Barbui et al[13] examined 501 patients with dysthymia. In this extensive sample, 81 percent of participants suffered from the early-onset subtype. The focus of the study was to compare healthcare utilization between the two subtypes of dysthymia. While the use of outpatient consultations, laboratory studies, and diagnostic procedures was similar between the two groups, the subsample with early-onset dysthymia experienced more inpatient psychiatric admissions, resulting in a higher total cost per patient in this subgroup.

What do these empirical findings tell us? First, and importantly, compared to patients with late-onset dysthymia, those with early-onset symptoms are far more likely to harbor psychiatric comorbidity, both on Axis I and Axis II. Axis I disorders predominantly reside in the domains of mood, anxiety, and substance use disorders. Axis II disorders predominantly reside in the domains of Cluster B (e.g., borderline and histrionic personality disorders) and Cluster C (e.g., avoidant and dependent personality disorders) disorders. Second, early-onset patients appear to experience more overall treatment exposure, including outpatient and inpatient interventions. Third, early-onset patients are less stress-resilient (i.e., more childhood adversity, greater likelihood of emotional coping styles, and greater stress responsivity). Finally, the family histories of those with early-onset dysthymia appear to be more riddled with mood disorders. These differences are summarized in Table 1.

It is important to note that we could not locate a single study that purported no differences between these two subtypes of dysthymia. From our experience with various reviews of the empirical literature, this is somewhat novel.

Clinical Implications

We believe that the clinical implications regarding the two subtypes of dysthymia are fairly evident and straight-forward. Patients with early-onset dysthymia are more difficult to treat. They exhibit more comorbidity and have more extensive treatment histories.

In examining how this observation affects mental health and primary care clinicians, we suspect that there may be differences in population loading in these two settings. It appears that the majority of patients with mental health problems, including depression, are initially evaluated and treated in the primary care setting. We suspect that as traditional treatment efforts dwindle, these more difficult, chronically depressed patients are referred to psychiatry. Thus, patients with early-onset dysthymia may be relatively over-represented in psychiatric settings. In addition, in psychiatric settings, these individuals typically present with double depression, which foreshadows a potentially challenging treatment course.

Caveats

In presenting these data and conclusions, we must broach two important caveats. First, individuals with dysthymia, either early or late-onset, are likely to be a clinically heterogeneous group. As an example, researchers and clinicians are still attempting to determine the validity and role of depressive personality disorder in relationship to dysthymia, particularly the early-onset subtype. Markowitz et al[14] state that depressive personality disorder appears to be an unstable diagnosis, and that the two appear to be related but different diagnostic constructs. Likewise, in their study, Phillips et al[15] found that 63 percent of participants with depressive personality disorder did not have either subtype of dysthymia. These impressions and findings suggest that chronic depression is likely to be a broad designation for various types of longstanding mood disorders, some of which may be characterologically based. Therefore, while we present dysthymic individuals as simply early versus late-onset, there is likely to be far greater heterogeneity within both subgroups.

A second potential confound in these studies is the self-declaration of the onset of symptoms. While it appears that early-onset patients are more complex, it may be that this very complexity contributes to a distorted recollection of onset. For example, in a patient with borderline personality, the attendant extremist cognitive style may promote the patient’s misperception that, “I have always felt this way.”

Conclusions

The designation of early- versus late-onset dysthymia made its initial appearance with the introduction of the DSM-III-R.[2] Since that time, a number of studies have, within the same study, compared these two subtypes. In all studies, investigators have found meaningful clinical differences. These differences relate to psychiatric comorbidity, treatment utilization, psychological resilience, and family histories of mood disorders. Importantly, to our knowledge, no study has reported an absence of differences. From a clinical perspective, these differences indicate that, compared to late-onset dysthymia, early-onset dysthymia is more challenging to treat. This is an important and unwavering distinction for both mental health and primary care clinicians.

References
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