Mood Disorders

Description

Major depressive disorder (MDD) is characterized by a distinct period of at least 2 wk (an episode ) in which there is a depressed or irritable mood and/or loss of interest or pleasure in almost all activities that is present for most of the day, nearly every day ( Table 39.1 ). Major depression is associated with characteristic vegetative and cognitive symptoms, including disturbances in appetite, sleep, energy, and activity level; impaired concentration; thoughts of worthlessness or guilt; and suicidal thoughts or actions. Major depression is considered mild if few or no symptoms in excess of those required to make the diagnosis are present, and the symptoms are mildly distressing and manageable and result in minor functional impairment. Major depression is considered severe if symptoms substantially in excess of those required to make the diagnosis are present, and the symptoms are highly distressing and unmanageable and markedly impair function. Moderate major depression is intermediate in severity between mild and severe.

Persistent depressive disorder is characterized by depressed or irritable mood for more days than not, for at least 1 yr (in children and adolescents). As with major depression, this chronic form of depression is associated with characteristic vegetative and cognitive symptoms; however, the cognitive symptoms of persistent depression are less severe (e.g., low self-esteem rather than worthlessness, hopelessness rather than suicidality). As with major depression, persistent depressive disorder is characterized as mild, moderate, or severe ( Table 39.2 ).

Overall, the clinical presentation of major and persistent depressive disorders in children and adolescents is similar to that in adults. The prominence of the symptoms can change with age: irritability and somatic complaints may be more common in children, and energy, activity level, appetite, and sleep disturbances may be more common in adolescents. Because of the cognitive and linguistic immaturity of young children, symptoms of depression in that age-group may be more likely to be observed than self-reported.

The core feature of disruptive mood dysregulation disorder (DMDD) is severe, persistent irritability evident most of the day, nearly every day, for at least 12 mo in multiple settings (at home, at school, with peers). The irritable mood is interspersed with frequent (≥3 times/wk) and severe (verbal rages, physical aggression) temper outbursts ( Table 39.3 ). This diagnosis is intended to characterize more accurately the extreme irritability that some investigators had considered a developmental presentation of bipolar disorder, and to distinguish extreme irritability from the milder presentations characteristic of oppositional defiant disorder (ODD) and intermittent explosive disorder.

Other specified/unspecified depressive disorder (subsyndromal depressive disorder) applies to presentations in which symptoms characteristic of a depressive disorder are present and cause clinically significant distress or functional impairment, but do not meet the full criteria for any of the disorders in this diagnostic class.

Epidemiology

The overall prevalence of parent-reported diagnosis of depressive disorder in the United States (excluding DMDD) among 3-17 yr old children is approximately 2.1% (current) and 3.9% (ever); the prevalence rate increases to 12.8% (lifetime) for 12-17 yr olds. The male:female ratio (excluding DMDD) is approximately 1 : 1 during childhood and beginning in early adolescence rises to 1 : 1.5-3.0 in adulthood.

Based on rates of chronic and severe persistent irritability, which is the core feature of DMDD, the overall 6 mo to 1 yr prevalence has been estimated in the 2–5% range. In 3 community samples, the 3 mo prevalence rate of DMDD ranged from 0.8–3.3%, with the highest rates occurring in preschoolers (although DSM-5 does not permit this diagnosis until age 6 yr). Approximately 5–10% of children and adolescents are estimated to have subsyndromal (unspecified) depression .

Clinical Course

Major depression may first appear at any age, but the likelihood of onset greatly increases with puberty. Incidence appears to peak in the 20s. The median duration of a major depressive episode is about 5-8 mo for clinically referred youth and 3-6 mo for community samples. The course is quite variable in that some individuals rarely or never experience remission, whereas others experience many years with few or no symptoms between episodes. Persistent depressive disorder often has an early and insidious onset and by definition, a chronic course (average untreated duration in both clinical and community samples: 3.5 yr).

Prepubertal depressive disorders exhibit more heterotypic than homotypic continuity; depressed children appear to be more likely to develop nondepressive psychiatric disorders in adulthood than depressive disorders. Adolescents exhibit greater homotypic continuity, with the probability of recurrence of depression reaching 50–70% after 5 yr. The persistence of even mild depressive symptoms during remission is a powerful predictor of recurrence; other negative prognostic factors include more severe symptoms, longer time to remission, history of maltreatment, and comorbid psychiatric disorders. Up to 20% of depressed adolescents develop a bipolar disorder; the risk is higher among adolescents who have a high family loading for bipolar disorder, who have psychotic depression, or who have had pharmacologically induced mania.

Differential Diagnosis

A number of psychiatric disorders, general medical conditions, and medications can generate symptoms of depression or irritability and must be distinguished from the depressive disorders. The psychiatric disorders include autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and bipolar, anxiety, trauma- and stressor-related, disruptive/impulse control/conduct, and substance-related disorders. Medical conditions include neurologic disorders (including autoimmune encephalitis), endocrine disorders (including hypothyroidism and Addison disease), infectious diseases, tumors, anemia, uremia, failure to thrive, chronic fatigue disorder, and pain disorder. Medications include narcotics, chemotherapy agents, β-blockers, corticosteroids, and contraceptives. The diagnosis of a depressive disorder should be made after these and other potential explanations for the observed symptoms have been ruled out.

Comorbidity

Major and persistent depressive disorders often co-occur with other psychiatric disorders. Depending on the setting and source of referral, 40–90% of youths with a depressive disorder have other psychiatric disorders, and up to 50% have ≥2 comorbid diagnoses. The most common comorbid diagnosis is an anxiety disorder and as such may reflect a common diathesis; other common comorbidities include ADHD and disruptive behavior, eating, and substance use disorders. The development of depressive disorders can both lead to and follow the development of the comorbid disorders.

Preliminary data suggest that DMDD occurs with other psychiatric disorders, including other depressive disorders, ADHD, conduct disorder, and substance use disorders, from 60–90% of the time. Because the symptoms of DMDD overlap in part with symptoms of bipolar disorder, ODD, and intermittent explosive disorder, by Diagnostic Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) convention, hierarchical diagnostic rules apply. Thus, bipolar disorder takes precedence over DMDD if a manic/hypomanic episode has ever occurred, and DMDD takes precedence over ODD and intermittent explosive disorder if full criteria for DMDD are met.

Sequelae

Approximately 60% of youths with MDD report thinking about suicide, and 30% attempt suicide. Youths with depressive disorders are also at high risk of substance abuse, impaired family and peer relationships, early pregnancy, legal problems, educational and occupational underachievement, and poor adjustment to life stressors, including physical illness.

Children with DMDD have displayed elevated rates of social impairments, school suspension, and service use. Irritability in adolescence has predicted the development of major depressive and dysthymic disorders and generalized anxiety disorder (but not bipolar disorder) 20 yr later, as well as lower educational attainment and income.

Etiology and Risk Factors

Current models of vulnerability to depressive disorders are grounded in gene and environment pathways. Genetic studies have demonstrated the heritability of depressive disorders, with monozygotic twin studies finding concordance rates of 40–65%. In families, both bottom-up (children to parents) and top-down (parents to children) studies have shown a 2-4–fold bidirectional increase in depression among first-degree relatives. The exact nature of genetic expression remains unclear. Cerebral variations in structure and function (particularly serotonergic), the function of the hypothalamic-pituitary-adrenal axis, difficult temperament/personality (i.e., negative affectivity), and ruminative, self-devaluating cognitive style have been implicated as components of biologic vulnerability. The great majority of depressive disorders arise in youths with long-standing psychosocial difficulties, among the most predictive of which are physical/sexual abuse, neglect, chronic illness, school difficulties (bullying, academic failure), social isolation, family or marital disharmony, divorce/separation, parental psychopathology, and domestic violence. Longitudinal studies demonstrate the greater importance of environmental influences in children who become depressed than in adults who become depressed. Factors shown to be protective against the development of depression include a positive relationship with a parent; better family function; closer parental supervision, monitoring, and involvement; a prosocial peer group; higher IQ; and greater educational aspirations.