DESCRIPTION (provided by applicant): In October 2004, the U.S. Food and Drug Administration (FDA) issued an advisory that antidepressants may be associated with an increased risk of suicidal thoughts and behaviors in children and adolescents. These warnings were prompted by its meta-analysis of all available randomized trials of antidepressants in this age group, in which patients randomized to antidepressants had nearly twice the rate of suicidal ideation or behavior relative to those given placebo. However, following the warnings clinicians, policymakers, and patients still need guidance on important treatment questions. We propose pooling 3 large cohorts of patients who initiated antidepressant therapy (Medicaid <65; Medicare 65+, and a province-wide population-based cohort in British Columbia) and link that use to data on their health care utilization. We will employ several innovative analytic methods to produce data that will help guide treatment choices. Specifically, we will answer the following research questions: 1) Identify the rates of suicidality in users of antidepressants in terms of class, specific agents, dosages, and durations of use. 2) Identify sociodemographic, clinical, and concomitant treatment factors that may modify the relationship between antidepressant use and suicidality. 3) Identify the impact of FDA actions on antidepressant utilization and clinical outcomes. 4) Identify patterns and potentially modifiable determinants of patient monitoring after initiation of therapy to help design and target future risk management interventions. 5) Assess and improve the accuracy of coding attempted suicide in hospital and emergency room admissions. This large pharmacoepidemiologic study by an experienced interdisciplinary team using multiple analytic methods will assess the most critical issues surrounding the safety of antidepressant therapy, and will provide guidance to develop and target better prescribing and risk management strategies.