The proposed study seeks to determine if among persons receiving periodontal treatment, those with clinical depression have poorer outcomes compared to those without clinical depression. Adult periodontitis is widespread in the population, periodontal case status has been associated with serious systemic conditions, the treatment of adult periodontitis is costly, and existing treatment modalities are of varying effectiveness. It is likely that depression plays a substantial role in determining periodontal treatment outcomes. A retrospective cohort study will be conducted using data obtained from the dental practices of Kaiser-Permanente Dental Program(KPDCP) in Portland, Oregon, allowing us to address the following research questions: l) Does clinical depression increase the risk of poor periodontal treatment outcomes? 2) Does treatment for clinical depression (including psychotropic medications) reduce the observed negative effect of depression status on periodontal treatment outcomes? 3) Do comorbidities of clinical depression(anxiety, alcohol and drug abuse, panic disorder, obsessive-compulsive disorder) increase the observed negative effect of clinical depression on periodontal treatment outcomes? This proposal investigates the effect of clinical depression on periodontal outcomes for the first time. Measures of depression status, comorbidities, treatment for depression, sociodemographics, medications and other potential confounders, and outcome of periodontal treatment will be collected and analyzed. 110 patients with depression and an equal number of non-depressed patients will be retrospectively followed for a period of l year during which time they underwent periodontal treatment. Periodontal treatment outcome will be assessed at the one year-follow-up by comparing the change in proportion of sites with pocketing equal to or > 4 millimeters in depth for depressed and non-depressed patients. Results of the study will be useful in determining the need for altered therapeutic intervention for clinically depressed periodontal patients, so as to improve the outcomes of periodontal treatment. These altered therapeutic interventions will serve to improve the quality, accessibility, and effectiveness of periodontal treatment for the population of periodontal patients suffering from clinical depression.