The goal of this study is to examine the effectiveness the selective serotonin reuptake inhibitor (SSRI) escitalopram (also known by the trade name "Lexapro") in reducing desire to self-harm and actual self-harming among young adults with borderline personality disorder who are also currently depressed. Subjects will receive either escitalopram or placebo for eight weeks. During this time subjects will be make weekly visits to see the psychiatrist and record their thoughts and feelings several times each day using an electronic diary.