## Diagnostic Distinction Between Bipolar I and II **Key Point:** The fundamental diagnostic criterion differentiating these two disorders is the severity and duration of the elevated mood episode. ### Bipolar Disorder I - Requires **at least one full manic episode** (duration ≥7 days, nearly every day) - Manic episodes are characterized by marked impairment in functioning or hospitalization - May or may not have depressive episodes - Psychotic features may be present but are NOT required for diagnosis ### Bipolar Disorder II - Requires **at least one hypomanic episode** (duration ≥4 days, nearly every day) - Hypomanic episodes do NOT cause marked impairment or require hospitalization - **Must have at least one major depressive episode** (this is mandatory) - Psychotic features are absent during hypomanic episodes **High-Yield:** The presence of a **full manic episode** (not hypomanic) is pathognomonic for Bipolar I. If a patient has only hypomanic episodes and depression, it is Bipolar II by definition. | Feature | Bipolar I | Bipolar II | |---------|-----------|----------| | **Elevated episode type** | Mania (full) | Hypomania | | **Duration** | ≥7 days | ≥4 days | | **Functional impairment** | Marked; often requires hospitalization | Mild to moderate; no hospitalization | | **Depressive episodes** | Optional | **Mandatory** | | **Psychotic features** | May occur | Absent | **Clinical Pearl:** A patient with only manic episodes and no depression is still Bipolar I. A patient with only hypomanic episodes and no depression does NOT meet criteria for Bipolar II—they would be classified as "Other Specified Bipolar and Related Disorder." [cite:DSM-5]
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