Impact of Comorbid Attention Deficit Disorder on the Direct Medical Costs of Treating Adults With Depression in Managed Care

Objective: To assess the impact of comorbid attention deficit disorder (ADD) on the direct medical costs of treating adults with depression in a mixed-model health maintenance organization.

Method: Annual mean and marginal health care costs were calculated for adults who were continuously enrolled at Group Health Cooperative during 2001 and who were diagnosed with depression, ADD, or both ADD and depression according to ICD-9-CM criteria during 2001.

Results: Of 249,874 adults continuously enrolled during 2001, 17,792 (7.1%) were diagnosed with depression, 1023 (0.4%) were diagnosed with ADD, and 454 (0.2%) were diagnosed with both depression and ADD. The mean total annual cost for an adult with a diagnosis of depression in 2001 exceeded that for the average adult enrolled in Group Health by 109% ($6029 vs. $2880). Of the $6029 mean total annual cost for treating an adult with a diagnosis of depression, $1872 (31%) was specifically attributable to depression. The presence of comorbid ADD resulted in ADD- and depression-attributed marginal costs approximately 29% higher than the costs specifically attributed to depression alone ($2418 vs. $1872). In fact, among patients with a diagnosis of ADD and depression, ADD- and depression-attributed costs approached the mean total cost of health care in the sample as a whole ($2880).

Conclusion: Depression is associated with high direct medical costs. The marginal costs of treating comorbid depression and ADD substantially exceed those of treating depression alone. These results underline the importance of considering the costs of comorbidities in estimating the economic burden of depression and developing cost-effective disease-management strategies.