Learning Objective
Understand the diagnostic criteria, clinical features, and treatment of Bipolar I, Bipolar II, and Cyclothymic disorder for an accurate USMLE Step 1 application.
Overview of Bipolar Disorders
| Disorder | Required Episodes | Key Features | Typical Course | Treatment | Notes |
|---|---|---|---|---|---|
| Bipolar I | ≥1 manic episode ± hypomanic or depressive episode | Mood elevation, irritability, distractibility, grandiosity | Mood and functioning usually normalize between episodes | Mood stabilizers: lithium, valproate, carbamazepine, lamotrigine; Atypical antipsychotics | Antidepressants may destabilize mood; high suicide risk |
| Bipolar II | ≥1 hypomanic episode + ≥1 major depressive episode | Hypomania: milder than mania; no psychosis | Mood and functioning usually normalize between episodes | Same as Bipolar I | Less severe; never has a full manic episode |
| Cyclothymic Disorder | ≥2 years of fluctuating hypomanic and mild depressive symptoms | Symptoms present ≥50% of the time; remissions <2 months | Chronic, less severe mood swings | Often, psychotherapy may use mood stabilizers if needed | Considered a milder form of bipolar disorder |
Key Points
- Manic episode: ≥1 week of elevated/irritable mood + ≥3 additional symptoms (e.g., grandiosity, decreased need for sleep).
- Hypomanic episode: ≥4 consecutive days; less severe than mania; no marked impairment or psychosis.
- Depressive episodes: ≥2 weeks of depressed mood or anhedonia plus ≥4 additional symptoms.
- Mood normalization occurs between episodes in Bipolar I and II.
- Cyclothymic disorder is persistent but subthreshold; it rarely progresses to full bipolar disorder.
