Introduction

Bipolar disorder, or manic-depressive illness, is characterized by moods that swing between two opposite poles:

Periods of mania with exaggerated euphoria, irritability, or both
Episodes of depression

Although chemical imbalances in the brain are a key component of bipolar disorder, it is a complex condition that involves genetic, environmental, and other factors.

Bipolar Disorder Categories

Bipolar disorder is classified according to the pattern and severity of the symptoms as bipolar disorder I, bipolar disorder II, or cyclothymic disorder. Patients with one type may develop another. Nevertheless, they are distinct enough to merit separate classifications, and some experts believe these conditions are actually separate disorders with different biologic factors that account for their differences.

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Bipolar Disorder I. Bipolar disorder I is characterized by at least one manic episode, with or without major depression. In 60 - 70% of cases, manic episodes precede or follow depressive episodes in a regular pattern. Episodes are more acute and severe than in the other two categories.

Without treatment, patients average four episodes of dysregulated mood each year. With mania, either euphoria or irritability may mark the phase. In addition, there are significant negative effects (such as sexual recklessness, excessive and impulsive shopping, and sudden traveling) on a patient's social life, performance at work, or both. Untreated mania lasts at least a week, and it can last for months. Typically, depressive episodes tend to last 6 - 12 months, if left untreated.

Bipolar Disorder II and Hypomania. Bipolar disorder II is characterized by predominantly depressive symptoms with occasional episodes of hypomania. Hypomania is similar to mania, but the symptoms (typically euphoria) are less severe and do not last as long.

Patients do not experience manic or mixed episodes, and most return to fully functional levels between episodes. However, bipolar II patients have a more chronic course, significantly more depressive episodes, and shorter periods of being well between episodes than patients with type I have. It is highly associated with the risk for suicide.