Abstract
BACKGROUND:
Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous condition with extensive psychiatric comorbidities. ADHD has been associated with substantial clinical and economic burden; however, little is known about the incremental burden specifically attributable to psychiatric comorbidities of ADHD in adults.
OBJECTIVE:
To assess the impact of psychiatric comorbidities, specifically anxiety and depression, on health care resource utilization (HRU) and costs in treated adults with ADHD in the United States.
METHODS:
A retrospective case-cohort study was conducted. Adults with ADHD were identified in the IQVIA PharMetrics Plus database (10/01/2015-09/30/2021). The index date was defined as the date of initiation of a randomly selected ADHD treatment. The baseline period was defined as the 6 months prior to the index date, and the study period as the 12 months following the index date. Patients with at least 1 diagnosis for anxiety and/or depression during both the baseline and study periods were classified in the ADHD+anxiety/depression cohort, whereas those without diagnoses for anxiety or depression at any time were classified in the ADHD-only cohort. Entropy balancing was used to create reweighted cohorts with similar baseline characteristics. All-cause HRU and health care costs were assessed during the study period and compared between cohorts using regression analyses. Cost analyses were also conducted in subgroups stratified by comorbid conditions.
RESULTS:
After reweighting, patients in the ADHD-only cohort (N = 276,906) and ADHD+anxiety/depression cohort (N = 217,944) had similar characteristics (mean age 34.1 years; 54.8% male). All-cause HRU was higher in the ADHD+anxiety/depression cohort than the ADHD-only cohort (incidence rate ratios for inpatient admissions: 4.5, emergency department visits: 1.8, outpatient visits: 2.0, and psychotherapy visits: 6.4; all P < 0.01). All-cause health care costs were more than 2 times higher in the ADHD+anxiety/depression cohort than the ADHD-only cohort (mean per-patient per-year [PPPY] costs in ADHD-only vs ADHD+anxiety/depression cohort: $5,335 vs $11,315; P < 0.01). Among the ADHD+anxiety/depression cohort, average all-cause health care costs were $9,233, $10,651, and $15,610 PPPY among subgroup of patients with ADHD and only anxiety, only depression, and both anxiety and depression, respectively.
CONCLUSIONS:
Comorbid anxiety and depression is associated with additional HRU and costs burden in patients with ADHD. Comanagement of these conditions is important and has the potential to alleviate the burden experienced by patients and the health care system.
Plain language summary
Patients with attention-deficit/hyperactivity disorder (ADHD) often also have other mental health conditions. We found that adult patients with ADHD who had anxiety/depression used 2-6 times more health care resources than those with ADHD only. These resources included hospitalizations and visits to emergency departments, outpatient clinics, specialists, and psychotherapists. The presence of anxiety/depression, particularly both together, also resulted in higher health care costs among patients with ADHD. ADHD management should consider other mental health conditions to minimize burden.
Implications for managed care pharmacy
This study provided insights on the drivers of health care resource utilization and costs associated with anxiety and depression in adults with ADHD in the United States. Knowledge on the incremental clinical and economic burden imposed by these common ADHD psychiatric comorbidities may facilitate the formulation of more targeted management approach and health plan policies. Strategies to comanage ADHD and psychiatric comorbidities have the potential to alleviate the substantial burden associated with adult ADHD.
Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental condition characterized by inattention, hyperactivity, and impulsivity that is estimated to affect 4.4% of adults in the United States.1,2 Adult patients with ADHD have been shown to have higher health care resource utilization (HRU) and costs compared with those without ADHD.3,4 At the societal level, excess direct health care costs attributable to ADHD have been estimated at $14.3 billion in the United States.5
ADHD is a heterogeneous condition with extensive psychiatric comorbidities,6 among which anxiety and depression are particularly common.7,8 A US national survey found that 40%-50% of adult patients with ADHD have comorbid anxiety and mood disorders (including depression).2 The presence of psychiatric comorbidities can complicate ADHD management,9,10 which may result in an increased burden on patients, clinicians, and the health care system at large.
Despite previous studies reporting excess HRU and costs associated with ADHD,3,4,11,12 little is known about the incremental clinical and economic burden specifically attributable to psychiatric comorbidities of ADHD in adults. A nationwide database study among hospitalized children and adolescents with ADHD in the United States reported that patients with comorbid depression had longer length of inpatient stay and tended to incur higher inpatient costs compared with those without the comorbidity.13 Another US survey found that children with ADHD who had comorbid anxiety, depression, and phobias had significantly greater odds of HRU than those with ADHD only.12 Although the results of these pediatric studies have highlighted the potential added burden attributed to psychiatric comorbidities of ADHD, there is a dearth of relevant data in adults.
Insights on the drivers of HRU and costs associated with comorbid anxiety and depression in adult patients with ADHD may provide a better understanding of the impact of these conditions on patients with ADHD and on the health care system. Research on this topic may also help raise awareness among stakeholders regarding the need to consider these comorbid conditions in clinical management, health plan policies, and therapeutic development. This study was therefore conducted to assess the impact of anxiety and depression on HRU and health care costs in US adults with ADHD. As HRU and costs could vary considerably between treated and untreated populations, this study focused on adults with ADHD who had received pharmacological treatment for ADHD.
Methods
STUDY DESIGN AND DATA SOURCE
A retrospective case-cohort study was conducted using the IQVIA PharMetrics Plus database covering the period from October 1, 2015, to September 30, 2021. The IQVIA PharMetrics Plus database contains integrated claims data of more than 190 million beneficiaries across the United States and includes information on inpatient and outpatient diagnoses and procedures, prescription fills, patients’ pharmacy and medical benefits, inpatient stays, and provider details. Additional data elements encompass dates of service, demographic variables, plan type, payer type, and start and stop dates of health plan enrollment. Data are deidentified and comply with the patient requirements of the Health Insurance Portability and Accountability Act of 1996; therefore, no institutional review board exemption or informed consent was required.
The index date was defined as the date of initiation of a randomly selected US Food and Drug Administration (FDA)–approved agent for the treatment of ADHD. Only treatments that were first initiated after the first ADHD diagnosis were eligible to be an index treatment; from all eligible treatments that were newly initiated after diagnosis, one was randomly selected as the index treatment, and its initiation date was the index date. This approach allowed the capture of a broad range of patients who were at different stages of their ADHD treatment journeys, which reflects more closely patients seen in routine clinical practice. The baseline period was defined as the 6-month period prior to the index date, and the study period was defined as the 12-month period following the index date.
PATIENT POPULATION
The sample selection flowchart is presented in Supplementary Figure 1 (204.8KB, pdf) (available in online article). Patients were included in the study if they met the following criteria: (1) had at least 2 ADHD diagnoses (International Classification of Diseases, Tenth Revision, Clinical Modification F90.x) recorded on a medical claim on distinct dates; (2) had at least 1 prescription fill for an FDA-approved pharmacological treatment for ADHD on or after the first ADHD diagnosis; (3) had continuous enrollment in a commercial health plan, including both medical and pharmacy coverage, during the baseline and study periods; and (4) were aged 18 years or older at the start of the baseline period.
STUDY COHORTS AND SUBGROUPS
Patients meeting the study criteria were classified into 2 study cohorts based on the presence of anxiety and/or depression (as defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition) at the initiation of a new treatment for ADHD. Patients with at least 1 diagnosis for anxiety and/or depression recorded on a medical claim during both the baseline and study periods were classified into the ADHD+anxiety/depression cohort, whereas those without diagnoses for anxiety or depression at any time were classified into the ADHD-only cohort.
For cost analyses, patients in the ADHD+anxiety/depression cohort were further stratified by comorbid conditions into subgroups of patients with ADHD who, during both the baseline and study periods, only had a diagnosis for comorbid anxiety (ie, the ADHD+only anxiety subgroup), comorbid depression (ie, the ADHD+only depression subgroup), or both anxiety and depression (ie, the ADHD+both anxiety and depression subgroup).
STUDY MEASURES AND OUTCOMES
Baseline characteristics, including demographic (eg, age and sex), clinical (eg, type of ADHD and comorbidities), and treatment characteristics (eg, pharmacological and nonpharmacological treatments received) were measured.
The study outcomes were all-cause HRU and health care costs during the study period. All-cause HRU included the following components reported per patient per year (PPPY): inpatient admissions, days with emergency department visits, days with outpatient visits, number of specialist visits (ie, psychiatrist or neurologist), and psychotherapy visits. All-cause health care costs consisted of medical costs (including inpatient, emergency department, and outpatient costs) and pharmacy costs. Costs PPPY were assessed from the payers’ perspective and adjusted to 2022 US dollars using the medical component of the Consumer Price Index.
STATISTICAL ANALYSES
Baseline characteristics and study outcomes were summarized using descriptive statistics. Means, medians, and SDs were reported for continuous variables; frequency counts and percentages were reported for categorical variables.
Entropy balancing was used to balance key baseline characteristics between the cohorts that may have an impact on the differences in outcomes; these included variables relating to ADHD disease and treatment characteristics to isolate the impact of anxiety/depression from differences in ADHD journeys at baseline. The cohorts were reweighted for the following characteristics: age, sex, region, health plan type, type of ADHD, calendar year of index date, number of agents received on or after ADHD diagnosis and before the index date, time from first observed ADHD diagnosis to first ADHD treatment, and time from first observed diagnosis to index date. Because the objective of the study was to assess the incremental burden of anxiety and depression in ADHD, comorbidities related to anxiety and depression were not balanced on as they may be a part of the disease burden. The balance of baseline characteristics between the cohorts was assessed using standardized differences, where less than 0.10 was considered well balanced.
Regression analyses were used to compare all-cause HRU and health care costs. Specifically, all-cause HRU was compared between the balanced cohorts using weighted negative binomial regression models with a log link, and the results were reported as incidence rate ratios (IRRs) along with their 95% CIs and P values. All-cause health care costs were compared between the balanced cohorts using weighted 2-part regression models. The first part of the model was a logistic model with a binomial distribution, and the second part was a generalized linear regression model with a log link and a γ distribution. To delineate the excess cost burden associated with each comorbid condition, additional regression analyses between the ADHD-only cohort and each of the balanced comorbidity subgroups (ie, ADHD+only anxiety, ADHD+only depression, and ADHD+both anxiety and depression) were also conducted.
Results
A total of 494,900 patients met the cohort-specific inclusion criteria, of whom 276,906 (56.0%) were included in the ADHD-only cohort and 217,994 (44.0%) were included in the ADHD+anxiety/depression cohort. Subgroups stratified by comorbid conditions included 100,215 patients with ADHD and only anxiety, 59,907 with ADHD and only depression, and 57,872 with ADHD and both anxiety and depression (Supplementary Figure 1 (204.8KB, pdf) ).
DEMOGRAPHIC AND CLINICAL CHARACTERISTICS
After reweighting, patient demographic and clinical characteristics were well balanced between cohorts (Table 1). In both cohorts, patients had a mean age of 34.1 years, and slightly more than half of patients were male (ADHD only: 54.8%; ADHD+anxiety/depression: 54.7%) and resided in the South region (both 51.4%). The majority of patients (76.5%) in both cohorts were covered by a preferred provider organization health plan.
TABLE 1.
Patient Demographic, Clinical, and Treatment Characteristics of Weighted Cohorts
| ADHD-only cohort (N = 276,906) | ADHD+anxiety/depression cohort (N = 217,994) a | Standardized differenceb | |
|---|---|---|---|
| Demographic characteristics as of index date | |||
| Age, mean ± SD [median], years | 34.1 ± 11.9 [31.7] | 34.1 ± 11.9 [31.9] | 0.00 |
| Sex, n (%) | |||
| Male | 151,626 (54.8) | 119,296 (54.7) | 0.00 |
| Female | 125,280 (45.2) | 98,698 (45.3) | 0.00 |
| Region, n (%)c | |||
| South | 142,413 (51.4) | 112,095 (51.4) | 0.00 |
| Midwest | 62,727 (22.7) | 49,393 (22.7) | 0.00 |
| Northeast | 45,639 (16.5) | 35,935 (16.5) | 0.00 |
| West | 25,944 (9.4) | 20,428 (9.4) | 0.00 |
| Health plan type, n (%)c | |||
| Preferred provider organization | 211,796 (76.5) | 166,728 (76.5) | 0.00 |
| Health maintenance organization | 36,338 (13.1) | 28,613 (13.1) | 0.00 |
| Point of service | 21,163 (7.6) | 16,662 (7.6) | 0.00 |
| Consumer-directed health care | 5,859 (2.1) | 4,612 (2.1) | 0.00 |
| Indemnity/traditional | 1,729 (0.6) | 1,363 (0.6) | 0.00 |
| Clinical characteristics during baseline | |||
| Time from first observed ADHD diagnosis to first ADHD treatment, mean ± SD [median], months | 0.9 ± 3.5 [0.0] | 0.9 ± 3.5 [0.0] | 0.00 |
| Time from first observed ADHD diagnosis to index date, mean ± SD [median], months | 14.9 ± 14.3 [10.4] | 14.9 ± 14.3 [10.1] | 0.00 |
| Number of ADHD treatments received between diagnosis and index date, mean ± SD [median] | 2.1 ± 2.1 [2.0] | 2.1 ± 2.1 [2.0] | 0.00 |
| 0, n (%) | 54,257 (19.6) | 42,711 (19.6) | 0.00 |
| 1, n (%) | 76,105 (27.5) | 59,908 (27.5) | 0.00 |
| ≥2, n (%) | 146,544 (52.9) | 115,375 (52.9) | 0.00 |
| Type of ADHD at most recent diagnosis on or prior to index date, n (%) | |||
| Inattentive | 141,964 (51.3) | 111,736 (51.3) | 0.00 |
| Combined presentation | 64,324 (23.2) | 50,684 (23.3) | 0.00 |
| Hyperactive | 8,354 (3.0) | 6,575 (3.0) | 0.00 |
| Other/unspecified | 62,264 (22.5) | 48,998 (22.5) | 0.00 |
| Psychiatric comorbidities, n (%)d | |||
| Anxiety | 0 (0.0) | 166,113 (76.2) | 2.53e |
| Depression | 0 (0.0) | 128,182 (58.8) | 1.69e |
| Sleep-wake disorders | 17,134 (6.2) | 33,310 (15.3) | 0.30e |
| Trauma- and stressor-related disorders | 13,188 (4.8) | 26,264 (12.0) | 0.27e |
| Substance-related and addictive disorders | 11,180 (4.0) | 26,138 (12.0) | 0.30e |
| Bipolar and related disorders | 5,708 (2.1) | 22,509 (10.3) | 0.35e |
| Obsessive-compulsive and related disorders | 1,258 (0.5) | 5,750 (2.6) | 0.18e |
| Neurodevelopmental disorders (excluding ADHD) | 1,815 (0.7) | 4,497 (2.1) | 0.12e |
| Feeding and eating disorders | 749 (0.3) | 3,255 (1.5) | 0.13e |
| Physical comorbidities, n (%)f | |||
| Hypertension | 24,833 (9.0) | 27,559 (12.6) | 0.12e |
| Obesity | 12,636 (4.6) | 15,596 (7.2) | 0.11e |
| Hypothyroidism | 12,097 (4.4) | 12,377 (5.7) | 0.06 |
| Cardiac arrhythmias | 4,861 (1.8) | 8,163 (3.7) | 0.12e |
| Treatment characteristics | |||
| ADHD treatment initiated at index date, n (%)g | |||
| Stimulant | 268,292 (96.9) | 203,862 (93.5) | 0.16e |
| Nonstimulants | 9,259 (3.3) | 14,889 (6.8) | 0.16e |
| Pharmacological treatments during baseline, n (%)g | |||
| ADHD treatments | 213,115 (77.0) | 169,756 (77.9) | 0.02 |
| Stimulants | 208,743 (75.4) | 162,992 (74.8) | 0.01 |
| Nonstimulants | 7,404 (2.7) | 11,577 (5.3) | 0.14e |
| Antianxiety agents | 17,360 (6.3) | 65,676 (30.1) | 0.65e |
| Antidepressants | 39,391 (14.2) | 148,486 (68.1) | 1.31e |
| Nonpharmacological treatments during baselineh | |||
| Psychotherapy, n (%) | 30,148 (10.9) | 94,808 (43.5) | 0.79e |
| Number of psychotherapy visits, mean ± SD [median] | 4.5 ± 5.7 [2.0] | 7.3 ± 7.9 [4.0] | 0.41e |
| Specialist visits, n (%) | 45,613 (16.5) | 90,962 (41.7) | 0.58e |
| Number of specialist visits, mean ± SD [median] | 2.4 ± 2.4 [2.0] | 3.6 ± 4.6 [2.0] | 0.34e |
a The ADHD+anxiety/depression cohort comprised patients with ADHD+only anxiety, ADHD+only depression, and ADHD+both anxiety and depression.
b A standardized difference of less than 0.10 was considered as well balanced.
c In both cohorts, less than 0.1% reported “Unknown.”
d Based on American Psychiatric Pub (2022). Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR).
e Indicates standardized differences greater than 0.10.
f Based on Elixhauser A, Steiner C, Kruzikas. D. HCUP Comorbidity Software. Healthcare Cost and Utilization Project (HCUP). October 2015. Agency for Healthcare Research and Quality, Rockville, MD. Available from: https://www.hcup-us.ahrq.gov/toolssoftware/comorbidity/comorbidity.jsp#download.
g Categories are not mutually exclusive.
h Calculated among those with at least 1 visit.
ADHD = attention-deficit/hyperactivity disorder.
At the most recent diagnosis prior to the index date, the most frequently observed ADHD type in both cohorts was inattentive ADHD (both 51.3%), followed by the combined presentation (ADHD only: 23.2%; ADHD+anxiety/depression: 23.3%) and hyperactive ADHD (both 3.0%). The mean time from first observed ADHD diagnosis to index date in both cohorts was 14.9 months, during which patients received a mean of 2.1 ADHD treatments.
During the baseline period, an overall higher proportion of patients in the ADHD+anxiety/depression cohort had comorbidities relative to the ADHD-only cohort. The most prevalent psychiatric comorbidities with a standardized difference of greater than 0.10 between the study cohorts included anxiety (ADHD only: 0.0% vs ADHD+anxiety/depression: 76.2%), depression (0.0% vs 58.8%), sleep-wake disorders (6.2% vs 15.3%), trauma- and stressor-related disorders (4.8% vs 12.0%), substance-related and addictive disorders (4.0% vs 12.0%), and bipolar and related disorders (2.1% vs 10.3%). The most prevalent physical comorbidities with a standardized difference of greater than 0.10 between the cohorts were hypertension (9.0% vs 12.6%), obesity (4.6% vs 7.2%), and cardiac arrhythmias (1.8% vs 3.7%).
TREATMENT CHARACTERISTICS
As index treatment, most patients received stimulants in both cohorts (ADHD only: 96.9%; ADHD+anxiety/depression: 93.5%; Table 1). During the baseline period, the proportion of patients treated with ADHD pharmacological treatments was 77.0% in the ADHD-only cohort (of whom 97.9% [208,743 of 213,115] received stimulants) and 77.9% in the ADHD+anxiety/depression cohort (of whom 96.0% [162,992 of 169,756] received stimulants).
Compared with the ADHD-only cohort, more patients in the ADHD+anxiety/depression cohort received antianxiety agents (6.3% vs 30.1%), antidepressants (14.2% vs 68.1%), and nonpharmacological treatments, including a higher proportion of patients with psychotherapy visits (10.9% vs 43.5%) and specialist visits (16.5% vs 41.7%), during baseline.
HRU
All-cause HRU was significantly higher in the ADHD+anxiety/depression cohort than in the ADHD-only cohort across components (Figure 1). Relative to patients in the ADHD-only cohort, those in the ADHD+anxiety/depression cohort had a higher incidence rate for inpatient admissions (IRR = 4.53), emergency department visits (IRR = 1.75), outpatient visits (IRR = 2.03), specialist visits (IRR = 3.63), and psychotherapy visits (IRR = 6.43) (all P < 0.01).
FIGURE 1.
All-Cause HRU During the Study Period
HEALTH CARE COSTS
All-cause health care costs were more than 2 times higher in the ADHD+anxiety/depression cohort than in the ADHD-only cohort (Figure 2). The mean all-cause health care costs PPPY were $5,335 in the ADHD-only cohort vs $11,315 in the ADHD+anxiety/depression cohort (mean difference: $5,979; P < 0.01). The cost difference was driven by both medical costs ($3,014 vs $7,627; P < 0.01) and pharmacy costs ($2,321 vs $3,688; P < 0.01).
FIGURE 2.
All-Cause Health Care Costs During the Study Period
When stratified by comorbid conditions, patients in each of the comorbidity subgroups incurred significantly higher all-cause health care costs than those with ADHD only (Figure 3). The mean all-cause health care costs PPPY were $9,233 among those in the ADHD+only anxiety subgroup, $10,651 among those in the ADHD+only depression subgroup, and $15,610 among those in the ADHD+both anxiety and depression subgroup (mean differences relative to the ADHD-only cohort were $3,897, $5,315, and $10,274, respectively; all P < 0.01).
FIGURE 3.
All-Cause Health Care Costs During the Study Period: Subgroup Analysis
Discussion
This US retrospective case-cohort study has illustrated the incremental HRU and cost burden attributable to comorbid anxiety and/or depression in adult ADHD using a large database. Overall, patients with ADHD and these comorbidities were found to have higher rates of psychiatric and physical comorbidities than those with ADHD only. Although more than 90% of patients with ADHD, irrespective of the presence of psychiatric comorbidities, had received stimulants, those with comorbid anxiety and/or depression were frequently also treated with antianxiety agents and antidepressants and had more psychotherapy and specialist visits than those with ADHD only. Comorbid anxiety and/or depression were associated with approximately 2- to 6-times-higher rates of HRU. Notably, increased outpatient and psychotherapy/specialist visits among those with ADHD comorbidities may point to more complex management (eg, longer time to find the optimal treatment, potentially more complications due to combined use of medications to treat ADHD and the comorbidities),10 whereas increased acute HRU may suggest more severe disease course.
The presence of comorbid anxiety and/or depression among patients with ADHD also resulted in more-than-2-times-higher annual health care costs, with the excess cost burden being the greatest among those with both comorbid conditions. The increased medical costs may reflect the observed increased HRU in these patients, whereas the increased pharmacy costs may be related to costs of additional medications received for the comorbid conditions. Although statistically significant differences are expected with large sample sizes, the large differences in all-cause HRU and health care costs across cohorts in this study were also practically meaningful. To contextualize the cost burden using a simulated health plan of 100,000 lives, a $5,979 excess cost incurred by patients with ADHD and comorbid anxiety and/or depression equates to approximately $8.7 million of incremental cost beyond ADHD alone in the health plan (ie, 100,000 lives × 4.4% prevalence of ADHD in adults2 × 75.0% initiated treatment × 44.0% had ≥1 diagnosis for anxiety, depression, or both based on proportions in the current study; Figure 4). Altogether, the findings of this study provide insights on the drivers of HRU and costs associated with comorbid anxiety and/or depression among adult patients with ADHD and highlight the unmet medical needs in this patient population.
FIGURE 4.
Incremental Cost of Comorbid Anxiety and/or Depression in ADHD Relative to ADHD Alone in a Simulated Health Plan
The burden of ADHD has been demonstrated in prior studies evaluating the clinical and economic burden borne by adult patients with ADHD compared with their counterparts without ADHD,3-5,14,15 but few studies have evaluated the incremental burden imposed by common ADHD psychiatric comorbidities. A US retrospective study assessing the cost of illness in adult ADHD found a significantly higher rate of psychiatric comorbidities in a subgroup of patients with ADHD and comorbid depression compared with those with ADHD only. The authors of that study suggested that the higher rates of comorbidities in the comorbid depression subgroup may drive HRU and costs, although no specific analyses were conducted to confirm the hypothesis.3 The current study isolated the impact of common ADHD psychiatric comorbidities such as anxiety and depression on HRU and costs, and the results are in accordance with the above hypothesis that these comorbidities impose an excess clinical and economic burden in patients with ADHD. Another US electronic medical record–based pre-post study found that among patients with ADHD who were later diagnosed with 1 or more psychiatric comorbidities, HRU rates and costs incurred by the patients increased in the 12-month period after vs before the psychiatric comorbidity diagnoses.16 Despite differences in study design precluding the direct comparability of the results, the findings of the aforementioned study and the current study both support that psychiatric comorbidities result in excess HRU and costs incurred by patients with ADHD. Contrary to the previous study that examined the combined impact of all psychiatric comorbidities, the current study focused on 2 of the most common ADHD comorbidities (ie, anxiety and depression), which may facilitate the formulation of a more targeted management approach and health plan policies.
The bulk of our knowledge on ADHD and its management approach stems from pediatric research. However, ADHD in adults can be associated with different challenges than those in children and adolescents, such as higher prevalence of psychiatric comorbidities2,17 and functional impairment,7,18 potentially because of increasing life responsibilities and stressors.6,19 Furthermore, adult ADHD has been estimated to account for nearly $123 billion of excess societal cost in the United States, of which approximately 86% is attributable to indirect costs such as unemployment and loss of productivity.5 It should also be noted that the societal cost of anxiety and that of depression, separately, is also substantial among adults in the United States.20-23 The presence of both conditions together may further increase the magnitude of the societal cost compared with each condition alone, as seen in the trends of the health care costs associated with these comorbidities observed in the current study. Thus, the impact of psychiatric comorbidities in adult ADHD is likely huge and extends beyond the individual and health care system burden assessed here.
Given the high prevalence and considerable impact of psychiatric comorbidities, the consideration of these comorbidities should become an integral part of ADHD management in adults.24,25 For instance, incorporating therapies that aim to improve psychosocial functioning of patients26,27 may help increase patients’ work performance and elevate their self-esteem, which may in turn reduce anxiety and depressive symptoms. Treatment options that target symptoms of both ADHD and psychiatric comorbidities may be explored,10,28 taking into account potential drug-drug interactions or adverse effects of medications, as some existing ADHD medications have been associated with mood fluctuations that may exacerbate the severity of symptoms in patients with ADHD and comorbid anxiety or depression.7,10 Early and optimal treatment of ADHD has also been shown to reduce the risk of developing certain psychiatric comorbidities.29 With appropriate strategies, comanagement of ADHD and psychiatric comorbidities has the potential to alleviate the substantial burden associated with adult ADHD.
LIMITATIONS
The findings of this study should be interpreted in light of some limitations. First, the current study included commercially insured patients; hence, the sample may not be representative of the entire ADHD population in the United States. Second, inherent limitations of retrospective database using claims data may include the risk of data omissions, coding errors, and the presence of rule-out diagnosis. Third, although cohorts and subgroups were balanced on observable characteristics, there might be residual confounding due to unobservable confounders; therefore, no causal inference can be made.
Conclusions
This study illustrates the added burden of common comorbid psychiatric conditions on HRU and health care costs in the US adult ADHD population. Among adult patients with ADHD, having anxiety and/or depression was associated with a statistically significantly increased risk of inpatient admissions, emergency department visits, and outpatient visits, as well as psychotherapy/specialist visits. The increased HRU translated to significantly increased health care costs, driven by both medical and pharmacy costs. Given the high prevalence and substantial impact of psychiatric comorbidities in ADHD, comanagement of these conditions is crucial and has the potential to alleviate the burden experienced by patients and the health care system.
ACKNOWLEDGMENTS
Medical writing assistance was provided by Flora Chik, PhD, MWC, an employee of Analysis Group, Inc., and funded by Otsuka Pharmaceutical Development & Commercialization, Inc.
All named authors meet the International Committee of Medical Journal Editors criteria for authorship for this article, take responsibility for the integrity of the work as a whole, and have given their approval for this version to be published.
Funding Statement
Financial support for this research was provided by Otsuka Pharmaceutical Development & Commercialization, Inc. The study sponsor was involved in several aspects of the research, including the study design, the interpretation of data, the writing of the manuscript, and the decision to submit the manuscript for publication.
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