Asthma is one of the most impairing diseases of childhood, affecting more than 6% of children.1 Each year, it is responsible for 14 million lost school days and $3 billion in treatment costs.1 The earliest definitions of asthma recognized the impact of psychological distress on the disorder. While most would agree that having a chronic illness increases the risk of depression, there is emerging evidence that depression may have an impact on the onset and course of asthma. Several mechanisms have been suggested as explanations for the association between the 2 disorders. Many of these models focus on the impact of depression on treatment adherence and risk-taking behaviors in adolescence (eg, smoking, binge drinking), which alter asthma control; however, studies have found that adherence models cannot explain all the effects of depression on asthma.2
Recent research found that compared with euthymic adults, depressed adults have reduced knowledge of their asthma and ability to identify the signs of worsening asthma.3 These findings suggest that depression may also impair asthma control by reducing a person's ability to identify symptom exacerbations in a timely fashion. Direct psychobiologic pathways among stress, emotions, and asthma severity have also been hypothesized. For example, it is thought that early psychosocial distress may affect the development of the immune system, thereby affecting the onset of asthma.4 However, this theory is more relevant to stressors during infancy than to the effects of depression later in childhood. In this regard, Miller and Wood5 have proposed that the autonomic dysregulation seen in depressed emotional states may potentiate vagally mediated asthma exacerbations.
The combination of depression and asthma has been associated with increased morbidity and mortality in adults and children.6-8 In a double-blind, placebo-controlled study, an improvement in depressive symptoms in asthmatic adults was associated with a reduction in asthma severity and frequency of corticosteroid use.9 While controlled treatment studies of depression have not been completed in asthmatic children, the efficacy of psychosocial interventions for stress reduction in this population has been evaluated.10 Biofeedback, cognitive-behavioral therapy, and progressive relaxation have been found to improve outcome, although there are few controlled efficacy studies. There is an increasing effort to screen for depression in children with asthma, since the identification of treatable comorbid conditions that worsen asthma severity may improve the long-term course of the disorder.Assessment
Up to 50% of adults with asthma will experience depression in their lifetime.9 Children with asthma also have increased rates of depression and anxiety,8,11,12 although findings vary across studies with regard to the exact prevalence of depression and the impact of mood symptoms on asthma severity. These discrepancies probably stem from the different measures used to assess depressive symptoms, with few studies integrating both child and parent reports with direct clinical observation. Many studies relied solely on the parent-report form of the Child Behavior Checklist (CBCL), which was designed to assess global functioning, not depression. Parents' ratings of their child's mood could be impacted by their own depression,12,13 and there is concern that parents of medically ill children may be hypervigilant about signs of depression in their child, limiting the reliability of parent reports.
Child self-report measures should not be affected by biases in parent reporting. To date, children's self-reports of depressive symptoms have been assessed primarily using the Children's Depression Inventory (CDI), which, unlike the CBCL, inquires about symptoms specific to pediatric depression. While the psychometrics of this scale have been well established in medically healthy populations, it has not been extensively validated in children with chronic medical illnesses. Moreover, in pediatric depression trials, young children tended to underreport depressive symptoms, compared with parents and clinicians.14 In asthma studies, children's reports of internalizing psychopathology correlated poorly with asthma severity.12,13
Clinician-driven ratings of depression would avoid the potential confounding factor of parent mood and are generally deemed more reliable than the child's report of his or her mood. However, these ratings have not been widely used in pediatric asthma studies. When implemented, most studies have used structured interviews, such as the Diagnostic Interview Schedule for Children, which do not require experienced raters who can integrate symptom reports with direct observation of the child. Many structured interviews rely on categorical definitions of depressive symptoms (either present or not) that do not adequately identify subthreshold depressive states and that have limited statistical power to detect correlations. Given these limitations, it is not surprising that several studies have failed to find a relationship between asthma severity and depressive symptoms.12,15
The Children's Depression Rating Scale-Revised (CDRS-R) has become the standard assessment tool for depression in pediatric antidepressant trials, including the much-publicized Treatment for Adolescents With Depression Study.14,16 In this scale, trained raters integrate information from direct observation, child report, and parent report into one composite score of depressive symptoms.17 The scale, which is modeled after the Hamilton Rating Scale for Depression in adults, yields a total score of 17 to 113; a score of 40 or above is considered to be a strong indicator of an impairing depressive state and a score of 30 or above indicates the presence of subthreshold depressive symptoms.
The CDRS-R has been shown to reliably detect meaningful depressive states in normal and psychiatric populations.18 Although it does require trained raters to administer reliably, it is less time-consuming than most structured interviews and provides a dimensional measure of depressive symptoms. Moreover, there do not appear to be problems with parent overreporting in nonpsychiatric samples.19 In a psychiatric setting where trained raters are available, the CDRS-R appears to be an excellent choice for assessing depressive symptoms in children with asthma, but it has not been well studied in this population.