The primary objective of this study is to measure the effects of patient cost-sharing on the initiation of adjunctive treatment and subsequent healthcare utilization and expenditures among a population of commercially insured adults on antidepressant therapy.

Inclusion Criteria:

• Adult patients (aged 18-64) will be selected from the MarketScan Commercial Database between January 1, 2004, and September 30, 2008, if they have at least two medical claims with a diagnosis of depression and at least one prescription fill for an antidepressant medication.

Exclusion Criteria:

• Patients who have any claim with a diagnosis of dementia, schizophrenia, delusional disorder, psychoses, pervasive development disorder, mental retardation, cerebral degenerations, Parkinson's disease, senility, manic depression, bipolar disorder, or major depressive disorder with psychotic symptoms.

Patients will be selected from the MarketScan Commercial Database between January 1, 2004 and September 30, 2008 (the last month of data available)