Borderline personality disorder (BPD) and major depression are highly interactive conditions, a new study from Harvard University-affiliated McLean Hospital finds. Specifically, the presence of BPD hinders a timely recovery from major depression, while, conversely, the presence of major depression hinders a timely recovery from borderline personality disorder, researchers say. Small but significant numbers of people across the U.S. have borderline personality disorder in combination with a second mental illness classified as a mood disorder (depression or a bipolar disorder). The presence of one of these conditions can significantly alter the course of the second condition over time. In a study published in 2014 in The Journal of Clinical Psychiatry, the team of researchers from McLean Hospital examined the ways in which borderline personality disorder and several forms of mood disorder impact each other in any given individual over the course of 10 years. Borderline Personality Disorder The term borderline personality disorder originally entered professional use because psychiatrists once believed that people affected by the condition had symptoms that placed them on the \u201cborder\u201d of the definitions for certain other known mental illnesses. Modern-day professionals no longer hold this point of view, but use of the term continues just the same. A person diagnosed with borderline personality disorder typically has problems in three main areas: the ability to regulate fluctuations in thought and mood, the ability to control momentary impulses and avoid risky behavior, and the ability to maintain lasting, durable social ties with others. Common manifestations of these problems include frequent angry or panicked outbursts in certain circumstances, repeated involvement in various forms of reckless behavior and repeated involvement in various forms of damaging, romantic and non-romantic relationship conflict. People with borderline personality disorder frequently have elevated chances of thinking about suicide, making suicide-oriented plans or engaging in overtly suicidal acts. In addition, the disease is often associated with the presence of other additional forms of mental illness, including substance use disorder, anorexia nervosa and other eating disorders, panic disorder and other anxiety disorders, bipolar disorder, major depression and other forms of depressive illness. Mood Disorder Mood disorder is an unofficial term that mental health professionals and the general public use to describe the full range of depressive disorders and the full range of bipolar disorders. These conditions get their common nickname because they center on seriously or severely dysfunctional changes in affected individuals\u2019 day-to-day moods or emotional states. In addition to major depression (major depressive disorder), other mood disorders classified by the American Psychiatric Association as depressive disorders include disruptive mood dysregulation disorder, persistent depressive disorder (alternately known as dysthymia), premenstrual dysphoric disorder and substance\/medication-induced depressive disorder. In addition to classic bipolar I disorder (sometimes informally termed manic depression), other mood disorders classified by the American Psychiatric Association as bipolar and related disorders include bipolar II disorder, cyclothymic disorder and substance\/medication-induced bipolar and related disorder. Mood Disorders and BPD In the study published in The Journal of Clinical Psychiatry, the McLean Hospital researchers used an examination of 223 people diagnosed with borderline personality disorder to analyze the long-term interactions of BPD and three mood disorders: major depression, bipolar I disorder and bipolar II disorder. One hundred sixty-one of the study participants had a combination of borderline personality disorder and major depression, while 34 had a combination of BPD and bipolar I disorder. The remaining participants had a combination of BPD and bipolar II disorder. For a 10-year timeframe between the years 1997 and 2009, the researchers tracked the simultaneous impacts of borderline personality disorder and mood disorder in each individual. Over the course of 10 years, the researchers found that study participants with BPD had a delayed remission from major depression; conversely, they found that the presence of major depression slowed recovery from borderline personality disorder. The researchers also concluded that the presence of BPD increases the speed at which a person in treatment relapses back into active major depression symptoms; conversely, they concluded that the presence of major depression increases the speed at which a person in treatment will relapse back into active BPD symptoms. The researchers concluded that borderline personality disorder does not interact to a large degree with bipolar I disorder or bipolar II disorder. The only exception to this conclusion is the ability of bipolar II disorder to delay effective recovery from BPD. The study\u2019s authors believe that effective treatment of coexisting borderline personality disorder and major depression may hinge on the initial success of efforts to address BPD symptoms. They also believe that people affected by coexisting BPD and bipolar disorder need separate treatments that reflect the separate effects of these illnesses.