Childhood Depression Research Paper

1. The Meaning Of The Term ‘Depression’ In Young People

The term ‘depression’ in children or adolescents can refer to three different, increasingly restrictive definitions. At the least restrictive level, ‘depression’ refers to a negative or low mood, such as sadness. In medical terms, if the low mood persists beyond an expectable duration of time, this is a single symptom. It may occur in isolation or in conjunction with other symptoms. At a more restrictive level, ‘depression’ refers to a particular set of symptoms that frequently occur together. Such a set of symptoms is designated a syndrome. For instance, children with low mood often simultaneously experience boredom, low energy, and social withdrawal, among other possible symptoms. Such a syndrome can be assessed at one point in time by the use of symptom review checklists. At the most restrictive level, ‘depression’ refers to a psychiatric disorder, characterized by a significant and persistent change in the child’s functioning. Depressive disorders have, in addition to a number of defining symptoms, a certain duration and course, a level of severity that causes considerable distress, and an impact on the daily functioning of the young person. Assessment of depressive disorders requires a comprehensive clinical interview, possibly accompanied by symptom checklists or rating scales.

Depression as a single symptom will not be a focus of this research paper. Instead the focus will be primarily on depression as a disorder, and secondarily on depression as a syndrome, since syndromal depression has been the subject of several important longitudinal studies among youths.

Depression is one of the psychiatric disorders in which disturbed mood is the core defining characteristic. Diagnoses of depression (unipolar depression) in the American Psychiatric Association (1994) nomenclature include Major Depressive Disorder and Dysthymic Disorder, both of which refer to conditions in which mood is dysphoric or low. In depression, children may report feeling sad, unhappy, bored or uninterested in usual activities, angry, or irritable, or may appear sad or tearful. By contrast, bipolar mood disorders, or manic-depressive disorders, are conditions in which mood fluctuates episodically between such dysphoric states and unusually elevated, irritable, or expansive mood states.

2. Recognition And Recent History

Recognition that depression occurs with considerable frequency in children and adolescents has been a relatively recent development. In the 1950s and 1960s, when psychoanalytic theory provided the primary conceptual model for psychiatric diagnosis and psychological assessment, clinicians rarely diagnosed depression in young people, partly because the development of superego and ego ideal functions, considered necessary to generate and maintain depression, was incomplete in youngsters. Child clinicians were also faced with the reality that their most common referral problems involved behavioral disorders or school performance problems, rather than mood problems. By the 1970s, there was recognition that depression might be ‘underlying’ such problems, but it was not until the emphasis on phenomenological or symptom-focused diagnosis that depression began to be assessed systematically in young people. Lewinsohn et al. (1993) have proposed that the study of affective disorders in children and adolescents really began in the 1970s when several sets of investigators, including Carlson, Cytryn, Kovacs, Poznanski, Puig-Antich, Rutter, and their colleagues demonstrated that such disorders do occur and can be reliably assessed in young people. This development corresponded to the shift in psychiatric assessment toward systematic review of presenting symptoms, and away from nondirective, inferential assessment based on play observations or patient narrative reporting.

Since the advent of symptom-driven diagnosis in US psychiatry in 1980, the same diagnostic criteria used to diagnose depressive disorders in adults have been applied to children and adolescents. At present, the diagnosis of Major Depressive Disorder (MDD) requires at least one episode in which the child has had five or more of the following symptoms, including one of the first two, for a minimum of two weeks: (a) depressed or irritable mood; (b) markedly diminished interest or pleasure in activities; (c) weight or appetite loss or gain; (d) insomnia or hypersomnia; (e) psychomotor agitation or retardation; (f) fatigue or loss of energy; (g) feelings of worthlessness or excessive guilt; (h) decreased ability to think, concentrate, or make decisions; (i) recurrent thoughts of death or suicide or a suicide attempt or plan. The diagnosis of Dysthymic Disorder (DD) is given if depressed or irritable mood is present most days for a year or more, and if mood disturbance is accompanied by two or more of six key symptoms: poor appetite or excessive eating, insomnia or hypersomnia, low energy or fatigue, low self-esteem, poor concentration or difficulty making decisions, and feelings of hopelessness. MDD and DD are not mutually exclusive, and some children or adolescents present with a long-standing DD, upon which an episode of MDD has been superimposed: a condition referred to as ‘double depression.’

Parallel to the application of adult criteria to childhood depression, there have been numerous studies in the psychopathology of depression, and in its treatment, which have applied concepts and research models from the adult field and extended them to children. To give just two examples, both cognitive factors known to characterize adult depression (e.g., distortions in thinking) and cognitive therapy, which is known to be effective for adult depression, have been studied in young people. Although the use of adult diagnostic criteria for child and adolescent depression is now conventional in research and clinical practice, there continues to be controversy regarding the developmental sensitivity and adequacy of this approach. In particular, the school of thought known as developmental psychopathology (Cichetti et al. 1994) is characterized by an emphasis on understanding the multiple contributions of developmental sciences toward understanding both normal development and disorders such as depression. Merely applying the same criteria and research concepts from adults to children does not adequately account for the interactive contributions of cognitive development, family processes, school environment, and biological development to the development of mood disorders. Developmental psychopathologists seek to go beyond merely establishing that depressed children differ from nondepressed children on a set of symptoms and associated features, and to determine the conditions and processes that contribute to these differences.

3. Prevalence And Gender Differences

Prevalence of depression in children and adolescents varies across studies, in part depending on whether a syndrome (elevated scores on a continuous scale) or a diagnosed disorder (based on parent and/or child interviews) serves as the measure of depression. Fleming and Offord’s (1990) review of studies showed that MDD in preadolescent children occurred in as low as 0.4 percent and as high as 2.5 percent of the samples. Upper estimates for adolescents were higher, with a range from 0.4 percent to 6.4 percent. Prevalence of DD in children ranged from 0.6 percent to 1.7 percent, and in adolescents from 1.6 percent to 8.0 percent. The subsequent Oregon Adolescent Depression Project (Lewinsohn et al. 1993) found a point prevalence of 2.57 percent for MDD and 0.53 percent for DD, and lifetime prevalence of 18.48 percent for MDD and 3.22 percent for DD in US high school students (mean age = 16.6 years).

Depression is associated with age and with gender (Birmaher et al. 1996a). Rates are higher in adolescents than in children. Phenomenology also differs to some extent by age, with adolescents with MDD more likely than children to have anhedonia, hypersomnia, weight change, or lethal suicide attempts. Among depressed children there is equal gender representation, but in adolescents the ratio is about two females to one male, similar to the pattern among adults. The reasons for gender differences in adolescent depression are the focus of considerable current research. Sociocultural pressures on girls, biological changes associated with puberty, and sex differences in cognitive coping mechanisms have been proposed as possible explanations.

4. Course Of Depressive Disorders In Childhood

Kovacs and her colleagues were the first to study the course of depressive disorders in prepubertal children. Their sample consisted of children who had been referred for clinical services, and was not an epidemiological sample. The average (mean) duration of the index episode of MDD in their sample was 32 weeks and half had recovered by nine months (median duration). For DD, however, the median duration of the episode was four years. Both MDD and DD children demonstrated a high likelihood of having a second depressive episode within a nine-year followup period, with the risk higher among DD than among MDD children (Kovacs 1996). By contrast, children diagnosed with an Adjustment Disorder with depressed mood (one or a few depressive symptoms in reaction to a stressor) were not at risk of developing MDD during follow up.

Data from the Oregon Adolescent Depression Project (Lewinsohn et al. 1993), with an epidemiological sample, indicated that there is an extraordinarily variable duration of MDD in teenagers. Mean episode duration was 26 weeks, but median was eight weeks, with a range of 2 to 520 weeks. Seventy-five percent of the adolescents recovered by 24 weeks. Overall, about 33 percent of the adolescents who recovered from their initial episode of MDD had a second episode within four years. Adolescents with onset of MDD before age 15.5 years had longer episodes and shorter times between recovery and relapse than did adolescents with later onset.

Using syndromal measures of depression assessed on rating scales or clinician-completed symptom checklists, studies both in the USA and in the UK have demonstrated that depression during the developmental period confers an increased risk of depression during adulthood. Harrington and his colleagues (Harrington et al. 1990) have shown that depressed young people followed up an average of 18 years into adulthood have nearly a fourfold increased risk of adult depression when compared to a control group matched for nondepressive childhood symptoms.

5. Comorbidity And The Risk Of Developing Bipolar Disorder

Studies from New Zealand, Puerto Rico, and the continental USA reviewed by Angold and Costello (1993) have shown that depression (either MDD or DD) in young people is very often accompanied by other disorders. The most common comorbid conditions in these studies were oppositional or conduct disorders and the various anxiety disorders. Rates of conduct or oppositional disorders in depressed children or adolescents ranged widely across studies, from 20 percent to 80 percent. Most studies showed rates of anxiety disorders between 30 percent and 50 percent, but some showed rates exceeding 70 percent. In the Oregon project, Lewinsohn and colleagues (1993) found that the most frequent comorbid diagnoses for depressed adolescents were anxiety disorder (21 percent) and substance use disorder (20 percent), with 12.4 percent of depressed teenagers having a disruptive behavior disorder.

Birmaher and colleagues (Birmaher et al. 1996a), in their review of the comorbidity literature, found that, except for substance use disorders, most of the other comorbid conditions developed before the MDD. However, conduct disorder was sometimes found to develop after MDD and to persist after resolution of the depression. Comorbid MDD and DD, in particular, have been found to predict longer depressive episodes, more suicidality, and worse social adjustment. The presence of comorbid anxiety disorders appears to raise the risk of suicidality and of substance abuse, and to be associated with poorer response to psychotherapy. There has been particular interest in comorbid depression and disruptive behavior disorders, perhaps because these represent a combination of two distinct types of disorders, internalizing and externalizing, that would not ordinarily be expected to co-occur. Birmaher and colleagues’ (1996a) review indicates that these young people are at increased risk for suicide attempts and adult criminality, and have poorer response to acute treatment, but also have more positive responses to placebo treatment and have fewer depressive recurrences.

Bipolar disorder includes distinct periods of depression and of mania. Because bipolar disorder is well recognized as distinct from unipolar depression, with a different course and different treatment requirements, it is important to assess the risk of developing bipolar disorder in depressed young people. Follow-up studies of clinically referred youths have varied in duration of follow-up period and in definition of bipolar disorder. They suggest that about 20 percent of adolescents with MDD go on to develop bipolar disorder, but the range of estimates to date varies widely. Factors that predict bipolar outcome include psychotic symptoms during the depressive episode, family history of bipolar disorder, and hypomanic reactions to antidepressant medication. There is conflicting evidence regarding the predictive utility of acute vs. prolonged onset of depression in predicting bipolar outcome. Both acute onset of severe depression in hospitalized adolescents and early onset of DD in (nonhospitalized) children have been associated with later bipolar outcome, suggesting there may be more than one path to a bipolar outcome.

6. Current Research Emphases: Psychosocial Correlates, Biology, And Treatment

Psychosocial correlates, biological correlates, and treatment efficacy and effectiveness are three areas of current research emphasis in childhood and adolescent depression. Correlates include an array of factors that are associated with and may make a causal contribution to depression or maintaining a depressive episode. Some psychosocial correlates, such as family factors and cognitive factors, can become targets of treatment in psychosocial intervention.

Compared to controls, the families of depressed young people are characterized by higher levels of parent–child and or marital conflict, poor parent–child communication, and more distant, less affectionate parent–child relationships (Birmaher et al. 1996a). The challenge for researchers is to determine whether these factors are specific to depression, and if so, whether they are causal.

A number of cognitive factors has been associated with depression in youths. These include cognitive distortions that emphasize negative interpretations of events, a tendency to attribute negative events to enduring and internal causes but positive events to transitory and external causes, low self-esteem, and low estimates of personal control and competence. Although such factors are present while youngsters are depressed, it is not clear whether they represent pre-existing risk factors or state-dependent correlates of the depressive episode. An important research question is to delineate the processes through which children acquire such cognitive characteristics.

Biological correlates of depression include family genetic factors and markers of a depressed state. Children of depressed parents are more likely to develop depression than are children of nondepressed parents. Studies in adults show a significant genetic component to the transmission of mood disorders, and family interaction studies suggest that depressed parents have deficits in parenting behaviors that raise the risk of poor adaptation in their children. Both genetics and experience, therefore, are likely involved in cross-generational transmission of depression.

A number of potential biological markers of MDD have been investigated, in the desire to clarify the biological basis of the disorder. Among these are secretion of growth hormone after pharmacological challenges, abnormalities in functioning of the hypothalamic–pituitary–adrenal axis, and abnormal sleep EEG patterns. Results to date do not suggest any single marker sufficiently sensitive to or specific to childhood or adolescent MDD that can be used for diagnostic purposes.

Effective treatment is a major current focus of research. Cognitive behavior therapy (CBT) involves working with the young person to understand and to modify thoughts and behaviors that are likely contributing to depression. Interpersonal psychotherapy (IPT) involves working with the young person to understand the impact of relationship or role conflicts on depression and to modify interpersonal patterns. There is considerable evidence to support the efficacy of CBT both for childhood and for adolescent depression, when compared to control conditions such as a waiting list (Birmaher et al. 1996b, Reinecke et al. 1998). Most of the child study subjects have been children with a depressive syndrome, and some of the interventions have been school-based. More of the adolescent studies have involved teenagers with a depressive disorder and have been clinic-based. There have been very few studies to date comparing CBT to other active treatments. IPT has also proven more effective than clinical monitoring for depressed adolescents, both in terms of symptom reduction and in terms of improved social functioning (Mufson et al. 1999).

Studies of older tricyclic antidepressant medications did not demonstrate efficacy in children or adolescents. A recent study by Emslie and his colleagues (Emslie et al. 1997) using fluoxetine, a selective serotonin reuptake inhibitor, did show a significantly better outcome for those on medication than for those receiving a placebo. As is true in the psychosocial treatment arena, research on medication treatment has been limited to acute or short-term treatment.

Numerous critical questions remain to be investigated. These include the relative efficacy of various psychosocial, medication, and combined treatments, the long-term efficacy of such treatments, optimal duration of treatment, and effectiveness of university- or laboratory-based interventions in the broader clinical world. It is not yet clear whether individuals who fail to respond to a first treatment will do better with an alternative. Finally, a major challenge to treatment research is to identify strategies and methods to address the comorbid conditions that so often accompany depressive disorders in young people.

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