Cost of illness and comorbidities in adults diagnosed with attention-deficit/hyperactivity disorder: a retrospective analysis.

Objective: This retrospective study assessed the cost of illness and medical and psychiatric comorbidities in adults with attention-deficit/hyperactivity disorder (ADHD) compared with adults without ADHD (matched 1:3) and adults with depression (1:1). Individuals with depression were included as a benchmark against which the burden of ADHD could be measured.

Method: Measures of health care and employment-related costs were compared to generate estimates of medical expenditures, workplace absences, and comorbidities in adults with ADHD (using ICD-9-CM codes) who were enrolled in employer-sponsored health plans throughout 2006. Individuals with ADHD (31,752) were matched with 95,256 non-ADHD controls. The majority of individuals with ADHD (n = 29,965) were also matched with an equal number of individuals with a depression diagnosis (using ICD-9-CM codes).

Results: In this adult population with ADHD enrolled in an employer-sponsored health plan, medical and psychiatric comorbidities were the primary drivers of health care utilization and cost. Of note, depression was significantly prevalent among those with ADHD compared to matched non-ADHD controls (14% vs 3.2%; P ≤ .0001). Subgroup analysis demonstrated that ADHD patients with depression had a significantly higher number of medical and other psychiatric comorbid illnesses including diabetes, hypertension, asthma, irritable bowel syndrome, bipolar disorder, anxiety, alcohol abuse, and substance abuse compared to those with ADHD alone (P ≤ .0001). Patients with ADHD incurred higher total annual health care expenditures than control subjects ($4,306 vs $2,418); approximately 15% of costs were paid by the patient. The total annual costs associated with productivity losses were also higher (driven by differences in short-term disability costs) in the ADHD group compared with controls ($4,403 vs $4,209).

Conclusions: Medical and psychiatric comorbidities were primary drivers of the direct health care cost associated with ADHD in adult patients. The present study demonstrated that the total costs of ADHD among adults are doubled when indirect costs associated with workplace productivity losses are included.