A total of 16.2% (n = 125) of youth with asthma met DSM-IV criteria for ≥1 anxiety or depressive disorders in the last 12 months with 68 (8.9%) meeting criteria for an anxiety disorder alone, 20 (2.5%) a depressive disorder alone, and 37 (4.8%) both an anxiety and depressive disorder. Compared to youth without an anxiety or depressive disorder, youth with any disorder were significantly more likely to be female, to have a parent with high school education or less, to have a parent who is not currently married, to be a Medicaid recipient, and have a higher PCDS score (). There were no differences in the modified HEDIS measure of severity between asthmatic youth with or without a disorder. There were also no significant differences among the three groups with any anxiety or depressive disorders.
Characteristics of Youth Stratified by Anxiety or Depressive Disorder Grouping (N = 767, unless otherwise specified)
In the unadjusted analyses, youth with a disorder had significantly more total primary care visits for mental health and non-asthma non-mental health reasons (). The youth with anxiety/depressive disorders had significantly more specialty outpatient mental health and ‘other’ outpatient visits, but significantly less specialty visits for asthma than youth without a disorder. Youth with a disorder had more emergency department (ER) visits due to mental health and other non-asthma related causes. Youth with any disorder also had significantly more pharmacy fills than those without a disorder; however, this increased utilization was not attributable to asthma medications.
Health Care Utilization for Youth with and without any Anxiety/Depressive Disorder
Because youth were sampled based on health care utilization, all youth in the sample had at least some costs during the study period. Most of these costs were in the outpatient setting. Only 5.6% of youth with an anxiety or depressive disorder and 3.4% of youth without a disorder had any inpatient costs (). Two youth with an anxiety or depressive disorder and four without had inpatient costs in a mental health setting. Youth with a disorder were more likely than youth with no disorder to have any outpatient mental health costs, ER costs, and out of pocket costs.
Number and Percent of Youth with Any Costs in Each Category, Unadjusted and Adjusted Tests for Anxiety / Depression Group Differences
In the first part of the model, eight cost categories had enough variation to be examined (). None of the interactions between asthma severity and depression/anxiety group approached significance and there was no evidence of an interaction between depression and anxiety (although due to the small sample sizes in some of the cells, this test was probably underpowered). Therefore, interaction terms were not included in the final models. The unadjusted analyses showed that in the outpatient mental health, ER, and patient out of pocket cost categories, having ≥1 anxiety/depressive disorder was significantly and independently related to the probability of having any costs. In adjusted analyses, only having any ER costs [OR = 1.92, 95% CI = 1.22 – 3.02, p = .005] and any outpatient mental health costs [OR = 2.62, 95% CI = 1.60 – 4.28, p < .001] were significantly different between the groups.
The unadjusted health cost data showed similar patterns across groups (). Youth with an anxiety/depressive disorder had significantly higher total outpatient, primary care, outpatient mental health care, ER, other outpatient, and lab and radiology costs.
Unadjusted Costs for Youth with and without Anxiety/Depressive Disorders
In part two of the 2-part model, we performed linear regressions using only those patients who had costs in a given category. All analyses controlled for asthma severity, child gender, parental marital status, parental education, Medicaid status, and PCDS. As with part one, none of the interaction terms approached significance and were not included in the final model. We found that the adjusted cost ratio of 18-month median total outpatient costs were 51% greater (95% CI – 4% to 118%) for youth with a depression diagnosis (with or without anxiety disorder), 36% higher for youth with at least 1 HEDIS asthma severity measure (95% CI – 18% to 58%), and 112% higher for youth with >2 HEDIS measures (95% CI – 69% to 166%). Due to the small proportion of youth hospitalized in this sample, the results of the regression analyses for total outpatient and total costs were very similar. Youth with an anxiety diagnosis alone did not have statistically significant higher median cost ratios than youth without an anxiety disorder in either analysis.
As can be seen in , the total effect of having an anxiety diagnosis on total health care costs was .26 (p = .009). However, when the effect of anxiety is mediated by depression, then the indirect effect of anxiety is only .13 and is non-significant (p = .25). The Sobel test was statistically significant (z = 2.80, p = .005) indicating significant mediation by depression in the relationship between anxiety and health care costs. The relationship between anxiety and depression is strong (coefficient = .32, p < .0001). Very similar results were found for total outpatient costs, which also had significant mediation by depression (Sobel test z = 3.02, p = 003), and total non-asthma-related costs (Sobel test z = 2.82, p = .005). As a sensitivity analysis we looked at the mediation of depression on health care costs by anxiety, and anxiety was not a significant mediator of the relationship between depression and costs (Sobel test z =1.36, p = .17).
Association between Anxiety and Health Care Costs with and without Depression in the Model