Background
In the American Psychiatric Association’s Diagnostic and Statistical Manual, Fifth Edition (DSM-5), persistent depressive disorder (dysthymia) represents a consolidation of DSM-IV-defined chronic major depressive disorder and dysthymic disorder. [1] Persistent depressive disorder is a depressive mood disorder characterized by a chronic course and an early and inisidious onset (i.e., in childhood, adolescence, or early adulthood). Early onset (i.e., before age 21) is associated with higher risk for comorbid personality disorders and substance use disorders.
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.)
Of note, an estimated 75% of people with dysthymia meet criteria for at least 1 major depressive episode, referred to as double depression. [3] Those with dysthymia who have depressive episodes tend to have longer periods of depression and spend less time fully recovered. [4] In a 10-year follow-up study of people with dysthymia, 75% experienced some (at least 2 mo) 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. [5]
Diagnostic criteria (DSM-5)
The specific DSM-5 criteria for persistent depressive disorder (dysthymia) are as follows: [1]
Depressed mood for most of the day, for more days than not, as indicated by either subjective account or observation by others, for at least 2 years. In children and adolescents, mood may be irritable and duration must be at least 1 year.
Presence, while depressed, of two (or more) of the following:
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Poor appetite or overeating
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Insomnia or hypersomnia
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Low energy or fatigue
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Low self-esteem
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Poor concentration and/or difficulty making decisions
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Feelings of hopelessness
During the 2-year period (1 year for children and adolescents) of the disturbance, the individual has never been without symptoms in Criteria A and B for more than 2 months at a time.
Criteria for major depressive disorder may be continuously present for 2 years.
There has never been a manic episode or a hypomanic episode, and criteria have never been met for cyclothymic disorder.
The disturbance is not better explained by a persistent schizoaffective disorder, schizophrenia, delusional disorder, or other specified or unspecified schizophrenia spectrum and other psychotic disorders.
The symptoms are not attributable to the physiological effects of a substance (e.g., a drug of abuse, a medication) or another medical condition (e.g., hypothyroidism).
The symptoms cause clinically significant distress or impairment in social, occupational, or other important areas of functioning.
As with other depressive disorders, persistent depressive disorder (dysthymia) can be given further specifiers:
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With anxious distress
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With mixed features
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With melancholic features
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With atypical features
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With mood-congruent psychotic features
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With mood-incongruent psychotic features
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With peripartum onset
Etiology
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:
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Genetic predisposition
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Biological factors - such as alterations in neurotransmitters, endocrine, or inflammatory mediators
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Chronic stress - particularly with feelings of hopelessness and/or helplessness
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Chronic medical illness
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Psychosocial factors - such as social isolation, losses
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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 [6]
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. [9]
Epidemiology
Frequency
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.
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. [10]
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.
Prognosis
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. [11, 12, 13, 14] Chronic stress is associated with more severe symptoms and a lower likelihood of recovery. [13]
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, as is the strategy with other mood disorders. [15, 16]
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. [17] 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. [18]
Additional concerns in dysthymia include the following:
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Increased mortality and morbidity from unrelated physical illnesses - dysthymia is associated with poorer self-rated health status [19]
Patient Education
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 websites contain additional patient information:
For patient education information, see the Depression Center, as well as Depression.
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The various outcomes of dysthymia.
