Comorbidity of Dysthymic Disorders in Children and Adolescents by Atilla Turgay, M.D. Many patients with dysthymic disorders also have associated comorbid disorders. A detailed history will provide insight into the comorbidity profile, cross-sectionally and developmentally. Dysthymic disorder should be addressed clinically, as it may cause long-term chronic unhappiness and poor quality of life for the patient.
Dysthymic disorder (DD) is a chronic mood disorder. The depressive mood in DD is generally less intense but more chronic than in major depressive disorder (MDD). Dysthymic disorder is characterized by a chronically depressed mood that occurs for most of the day (more days than not) for at least two years. Individuals with DD describe their mood as "sad" or "down in the dumps." During periods of depressed mood, at least two of the symptoms in the Table must be present.
Differences Between Adult and Child DD
In children, mood may be irritable rather than depressed, and the required minimum duration is one year, according to DSM-IV. In many adult patients, a general history review discloses that many DD symptoms started in early childhood, continued into adolescence and became further established in adulthood. The literature provides support for similarities between the symptomatology, comorbidity profile and negative impact on the individual and family in both child and adult forms of DD (Goodman et al., 2000).
A Quick Review of Prevalence Rates
Dysthymic disorder affects 3% to 6% of individuals in the community (Kessler et al., 1994; Weissman et al., 1988) and 22% to 36% of outpatients in mental health care settings (Klein et al., 1989; Markowitz et al., 1992). The few epidemiological studies on DD have reported a prevalence of 0.6% to 1.7% in children and 1.6% to 8.0% in adolescents (Garrison et al., 1992; Kashani et al., 1987a, 1987b; Lewinsohn et al., 1994, 1993).
Challenges in Diagnosing MDD and DD
A detailed history, with a major focus on mood disorders, should be obtained. Structured or semi-structured interviews or comprehensive symptom checklists covering all psychopathology (preferably completed by children, teachers and parents) will increase the reliability of the history and the diagnosis. Mental status examinations, with primary focus on the differential diagnosis of mood disorders, will establish a reliable diagnosis and determine the nature and severity of associated comorbid disorders. Chambers et al. (1985) provided a comprehensive review of the available semi-structured interviews, their indications, sensitivity and limitations. Sprafkin et al. (2002) outlined the reliability, validity and sensitivity of their DSM-IV-based rating scales, with age-specific forms for children, adolescents and adults.
The DSM-IV diagnosis of DD can be made only if the full year period of DD symptoms is free of major depressive episodes. If the chronic depressive symptoms include a major depressive episode during the initial two years, then the diagnosis is MDD chronic (if full criteria for depressive episode are met) or MDD in partial remission (if full criteria for major depressive episode are not met). After the initial two years of DD, a major depressive episode may be superimposed on the DD. In such cases of "double depression," both MDD and DD are diagnosed. Once a person returns to a dysthymic baseline, only DD is diagnosed. The diagnosis of DD is not given if the individual has ever had a manic episode, a mixed episode or a hypomanic episode.
Because the change in mood is generally less intense than in MDD, DD is often overlooked or misdiagnosed. Although the symptoms of DD are not as severe as in MDD, they can cause similar, if not more severe, impairment in psychosocial functioning (Kovacs et al., 1994). For a DSM-IV diagnosis of DD, a child must present with depressed mood or irritability on most days for a period of one year, as well as two other symptoms from the Table.
One of the most important challenges for clinicians is to clearly establish a longitudinal understanding of the boundaries between MDD and DD. Most cases of DD appear to manifest at an earlier age than MDD and in successive cohorts, according to DSM-IV. The differential diagnostic picture may be quite complicated, as DD may become MDD, while many patients with MDD who have not yet fully recovered often present as having DD.
Reviewing Rates of Comorbid Disorders
Depressive disorder is rarely a singular DMS-IV Axis I diagnosis in a clinical setting. Dysthymic disorders are commonly accompanied by significant comorbidities (Howland, 1993; Jaffe et al., 1994). Children with DD generally experience their first episode of MDD two to three years following the onset of DD, which suggests that DD may be a gateway to recurrent mood disorders and indicates the need for preventive interventions (Kovacs et al., 1994).
The rate of comorbid disorders associated with DD in the community may not be as high as those seen in clinical samples. The presence and nature of comorbid disorders play a very important role in treatment decisions and clinical outcomes for DD (Kovacs et al., 1997, 1994).
In a clinical study with 240 patients with DD (ages 4 to 18) Turgay et al. (2004) reported that the most common comorbidities were: attention-deficit/hyperactivity disorder (62.9%), oppositional defiant disorder (41.7%), conduct disorder (29.2%) and generalized anxiety disorder (GAD) (28.3%). The ADHD subtypes were reported as hyperactive impulsive, 0.7%; predominantly inattentive, 39.7%; and combined type, 59.6%. Only 8.75% of the patients had a singular diagnosis of DD. The authors cautioned that these rates may be higher than those seen in the general public, as their sample was taken from a large metropolitan ADHD clinic.
Approximately 42% to 75% of children and adolescents with DD have superimposed MDD (Lewinsohn et al., 1994). In addition, 50% have other pre-existing psychiatric disorders, including anxiety disorders (40%), conduct disorder (30%), ADHD (24%), and enuresis or encopresis (15%). Approximately 15% have two or more comorbid disorders (Ferro et al., 1994; Kovacs et al., 1994).
Masi et al. (2003) examined a clinical sample of 100 children and adolescents without any concurrent MDD. Anxiety disorders were frequently comorbid: 59% of patients had GAD; 28% had single phobias; 18% had separation anxiety; 14% had obsessive-compulsive disorder; 13% had social phobia; and 10% had panic disorder. Comorbid ADHD, oppositional defiant disorder and conduct disorder were reported in 35% of patients. Irritability, fatigue or loss of energy, low self-esteem, depressed mood, guilt, concentration difficulties, anhedonia, and hopelessness were present in more than 50% of participants. Most reported symptoms were in the emotional and cognitive, rather than somatic and vegetative, domains.
The Need for Larger Samples, Follow-up Studies
Of the few existing prospective longitudinal studies of DD, most have used small study groups and short (one- to two-year) follow-up periods (Barrett, 1984; Gonzales et al., 1985). Compared to patients with episodic MDD, patients with DD are less severely depressed at initial examination but exhibit higher levels of symptoms in follow-ups conducted six to 30 months later. Childhood DD has a protracted course, with a mean episode duration of approximately three to four years for clinical and community samples, and is associated with an increased risk for subsequent MDD, bipolar disorder (BD) and substance use disorders (Keller et al., 1988; Klein et al., 1998; Kovacs et al., 1997, 1994). The presence of MDD and other psychiatric disorders may increase the duration of DD, lower response rate and worsen the outcome (Klein et al., 1998; Kovacs et al., 1997; Turgay et al., 2004).
Treating DD and Comorbid Disorders
There are relatively few controlled trials to provide evidence-based treatment recommendations. Single DD without any other comorbidity may respond to psychosocial (Kovacs and Bastiaens, 1995) or psychopharmacological interventions or the combination of the two (Kashani et al., 1987b; Kovacs et al., 1997, 1994; Weissman et al., 1988). Treatment of common comorbidities are reviewed below.
Dysthymic disorder and anxiety disorders. Cognitive or psychodynamic therapies may be useful in treating both depressive and anxiety symptoms. Selective serotonin reuptake inhibitors may help both anxiety disorders and MDD (Birmaher et al., 1994). Tricyclic antidepressants and bupropion (Wellbutrin) may help both ADHD and MDD (Findling, 1996). The SSRIs may be used to treat both MDD and OCD and have also been shown to treat adult DD and MDD (Kocsis et al., 1997; Thase et al., 1996). Although there is some support in the literature that this may be true for children and adolescents, further research is needed in this area. An integrative approach, bringing together crises intervention, individual and family therapy, and psychoactive medication may alleviate depressive symptoms and reduce the risk of suicide (Turgay, 1989).
Dysthymic disorder with BD. A small number of patients with DD may develop BD during follow-up. Manias tend to develop early, whereas hypomanias are evenly distributed across the follow-up period. Patients with both DD and a lifetime history of MDD were significantly more likely to have recurrent major depressive episodes than were patients with episodic MDD (Birmaher et al., 2002; Keller et al., 1988). Patients may require mood regulators and/or lithium (Eskalith, Lithobid) (Versiani, 1998).
Depressive disorder, ADHD and other disruptive behavior disorders. Dysthymic disorder is commonly associated with ADHD and other disruptive behavior disorders, including oppositional defiant disorder and conduct disorder. The treatment of ADHD with psychostimulants may also improve dysthymic symptoms. Patients with DD and conduct disorder and severe aggressive behaviors, with or without ADHD, may respond well to risperidone (Risperdal) (Snyder at al., 2002; Turgay, 2004; Turgay et al., 2004).
Dysthymic disorder is a chronic, serious mental disorder in children and adolescents with a complicated clinical picture and limitations for sufficient recovery. Research in symptomatology, comorbidity, treatment response and long-term outcome is limited. Early identification and effective treatment for DD and any comorbidities are essential for good treatment response. For most of the comorbidities, there are many effective treatment options available.
The complicated nature of DD with associated multiple psychopathologies requires comprehensive treatment with close monitoring and long-term follow-up plans. Whether the early and effective treatment of DD prevents the later development of MDD and other commonly associated comorbid disorders can be investigated with carefully controlled, long-term follow-up studies with various alternative treatment approaches. It is important to regard DD as a serious and complex disorder in children and adolescents that requires comprehensive assessment and integration of effective treatment strategies.
Dr. Turgay is a child, adolescent and adult psychiatrist. He is currently the chief of medical staff and director of psychiatric research at the Scarborough Hospital. He is also a professor at the University of Toronto, Faculty of Medicine.
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