Dysthymic Disorder 

Dysthymic disorder is a depressive mood disorder characterized by a chronic course and an insidious onset. Many people with dysthymia describe lifelong depression. (See Presentation.)

By definition, this condition has a duration of at least 2 years (1y in adolescents and children). It is manifested as a depressed mood for most of the day, occurring more days than not, and is accompanied by at least 2 of the following symptoms (see Presentation):

• Poor appetite or overeating
• Insomnia or hypersomnia
• Low energy or fatigue
• Low self-esteem
• Poor concentration
• Difficulty making decisions
• Feelings of hopelessness

To diagnose dysthymia, any major depressive episodes must not have occurred in the first 2 years of the illness (the first 1 year in children) and history of mania should not exist. The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR)^[1] allows transient euthymic episodes (periods of normal mood) of up to 2 months during the course of dysthymia.

The DSM-IV-TR categorizes dysthymia according to course specifiers. These include (1) early onset if symptoms began before age 21 years, (2) late onset if symptoms began at age 21 years or later, and (3) dysthymia with atypical features if symptoms include increased appetite or weight gain, hypersomnia, a feeling of leaden paralysis, and extreme sensitivity to rejection.

Although dysthymia was traditionally considered less severe than major depression, the consequences of dysthymia are increasingly recognized as grave; they include severe functional impairment, increased morbidity from physical disease, and increased risk of suicide. (See Prognosis.)

Anxious versus anergic dysthymia

Niculescu and Akisal proposed that dysthymia be divided into 2 subtypes: anxious dysthymia and anergic dysthymia. They described the subset of patients with anxious dysthymia as having pronounced symptoms of low self-esteem, undirected restlessness, and interpersonal rejection sensitivity. They also characterized these patients as help-seeking and more likely to make lower-lethality suicide attempts and to have a better response to selective serotonin reuptake inhibitors (SSRIs). Substances of choice for these patients include benzodiazepines, alcohol, marijuana, opiates, and possibly food. (See Treatment and Medication.)^[2]

This group is compared with persons who have anergic dysthymia, characterized by low energy, hypersomnia, and anhedonia. Patients with anergic dysthymia, the authors suggest, may have a better response to treatment with agents that increase norepinephrine or dopamine. (See Treatment and Medication.)

Dysthymia versus major depression

Dysthymia should be differentiated from major depression. In contrast to dysthymia, a diagnosis of major depression requires that at least 5 or more of the following symptoms have been present most of the day, every day, for the past 2 weeks:

• Depressed mood
• Loss of interest or pleasure in usual activities
• Significant weight loss or gain
• Insomnia or hypersomnia
• Psychomotor agitation or retardation
• Fatigue or loss of energy
• Feelings of worthlessness or excessive or inappropriate guilt
• Diminished ability to think or concentrate
• Recurrent thoughts of death or suicide

A diagnosis of major depression requires depressed mood and/or significant loss of interest or pleasure in activities. Differentiating dysthymia from major depression may be challenging in, for example, cases of major depression with a partial response to treatment.

Major depressive disorder, dysthymia, double depression, and some apparently transient dysphorias may all be manifestations of the same disease process. These varieties of depressive mood states, while distinct diagnostic entities, share similar symptoms and respond to similar pharmacologic and psychotherapeutic approaches. (See the diagram below.)^{[3, 4, 5, 6]}

Double depression

Of note, an estimated 75% of people with dysthymia meet criteria for at least 1 major depressive episode, referred to as double depression.^[7] Those with dysthymia who have depressive episodes tend to have longer periods of depression and spend less time fully recovered.^[8] In a 10-year follow-up study of people with dysthymia, 75% experienced some (at least 2mo) period of recovery from major depression; the mean time to recovery was 52 months from study entry. In this study, most (70%) of those who recovered experienced a relapse into another episode of depression, most commonly in the 3 years following recovery.^[9]

Depressive personality disorder

The DSM IV-TR also includes research criteria for depressive personality disorder, which may also be considered in the differential diagnosis of chronic low mood. Depressive personality disorder is characterized by a depressive disposition, introversion, a tendency toward self-criticism, and pessimistic cognitive processes, with fewer of the mood and neurovegetative symptoms seen in dysthymia. Dysthymia or depression may be comorbid with depressive personality disorder.^{[10, 11, 12]}

The cause of dysthymia, although not clear, is likely multifactorial. A biopsychosocial formulation considering the interplay of family history and other genetic factors, medical problems, psychological make-up and coping strategies, and social stressors, is helpful when considering the cause of dysthymia. Some examples of common contributing factors include the following:

• Genetic predisposition
• Biological factors - Such as alterations in neurotransmitters, endocrine, or inflammatory mediators
• Chronic stress - Particularly with feelings of hopelessness and/or helplessness
• Chronic medical illness
• Psychosocial factors - Such as social isolation, losses
• Ruminative coping strategies - These, as opposed to problem solving or cognitive restructuring strategies, are common among people with dysthymia and may predispose to or sustain dysthymia^[13]
• Antisocial, borderline, dependent, depressive, histrionic, or schizotypal personality traits - People diagnosed with these are at an increased risk for developing dysthymic disorder^{[14, 15]}

Electroencephalogram (EEG) and polysomnogram data demonstrate that about 25% of people who have dysthymia have sleep changes similar to those of persons who have major depression, including shortened rapid eye movement (REM) latency, increased REM density, and poor sleep continuity.

Physiology of dysthymia

The involvement of serotonin and noradrenergic systems in dysthymia is suggested by the disease’s positive clinical responses to serotonergic and noradrenergic medications, such as SSRIs, serotonin/norepinephrine reuptake inhibitors (SNRIs), and tricyclic antidepressants.

Abnormalities in neuroendocrine systems, especially thyroid and hypothalamo-pituitary-adrenocortical (HPA) systems, have been linked to depressive disorders in general, although the HPA axis has not been adequately studied in dysthymic disorder.

Cytokines and inflammation have also been implicated in major depression; however, a link to dysthymia has not been clearly established.

Occurrence in the United States

Best estimates are that the lifetime risk of significant depression exceeds 25%, with a point prevalence of about 5%. The lifetime community prevalence of dysthymia is 6%. Dysthymia affects an estimated 36% of patients in outpatient mental health treatment.

Race-related demographics

Minimal research has been performed to define differences in frequency and symptoms between races. One study, the National Health and Nutrition Examination Survey III (NHANES III), found that dysthymia is more common among African Americans and Mexican Americans than among Caucasians.^[16]

Sex-related demographics

For major depressive disorders, females outnumber males, with a female-to-male ratio of 2:1 during their childbearing years. Before puberty and after menopause, the 2 sexes appear to be affected about equally. In elderly people, dysthymia is relatively more frequent in females, but dysthymia adversely affects survival in males more than in females.

Age-related demographics

Most often, patients with dysthymia recall unexplained unhappiness in preadolescent childhood. Whether the DSM-IV-TR adequately addresses dysthymia in children and adolescents is a matter of some controversy.^[17]

Dysthymia is by definition chronic. Periods of depression or euthymia may occur during the course of the illness. A systematic review of epidemiologic studies found that 46-71% of persons with dysthymia reported remission at follow-up points ranging from 1-6 years.

Comorbidities, such as anxiety disorders and depressive personality disorder, are associated with lower recovery rates.^{[18, 10, 19, 12]} Chronic stress is associated with more severe symptoms and a lower likelihood of recovery.^[19]

With adequate treatment, substantial, prolonged improvement can be expected in most patients. Emphasis is increasing on the importance of striving for remission, rather than response, when treating depressive disorders.^[20]

Morbidity and mortality

Patients should be closely monitored for the emergence of major depression or bipolar disorder. Review of longitudinal studies showed that 76% of dysthymic children developed major depression and that 13% developed bipolar disorder over follow-up periods of 3-12 years.

Patients with dysthymia have a higher risk of employment problems, including decreased productivity and increased unemployment.^[21] A study found that at 6 months, 14% of patients with dysthymia were newly unemployed, compared with 2% new unemployment in the control group and 3% new unemployment in a group with rheumatoid arthritis.^[22]

Additional concerns in dysthymia include the following:

• Increased mortality and morbidity from unrelated physical illnesses - Dysthymia is associated with poorer self-rated health status^[23]
• Suicide, attempted or completed - Dysthymia significantly increases risk of suicide^{[24, 25]}

If possible, family members and other significant individuals should be helped to understand depression, to view the patient's complaints as symptoms of an illness, and to be sensitive to signs of major depression, with its risk of suicide. For example, an increase in irritability often heralds the progression from dysthymia to depression and may be apparent to people close to the patient before the patient is aware of the change.

The following Web sites contain additional patient information:

• WebMD, Dysthymia (Mild, Chronic Depression)
• Harvard Health Publications, Dysthymia
• MedlinePlus, Dysthymia
• Depression and Bipolar Support Alliance

For patient education information, see the Depression Center, as well as Depression.