Bipolar Disorder for USMLE Step 1 / COMLEX-USA Level 1
Bipolar Disorder Overview
- Types:
- Bipolar I Disorder: Characterized by one or more manic episodes, often alternating with major depressive episodes.
- Bipolar II Disorder: Presence of one or more hypomanic episodes and at least one major depressive episode.
- Cyclothymic Disorder: Milder form involving numerous periods of hypomanic symptoms and depressive symptoms lasting for at least 2 years.
Pathophysiology
- Genetic Factors: High heritability; multiple genes involved, often in pathways related to ion channel regulation and neurotransmitter systems.
- Neurotransmitter Imbalances:
- Increased Norepinephrine and Dopamine: Linked to manic episodes.
- Serotonin Dysregulation: Associated with both depressive and manic phases.
- Neural Circuitry: Dysregulation in the prefrontal cortex, limbic system, and basal ganglia implicated in mood regulation and emotional processing.
Clinical Features
- Manic Episode:
- Elevated or irritable mood, increased energy or activity for at least one week.
- Symptoms include inflated self-esteem or grandiosity, decreased need for sleep, more talkative than usual, flight of ideas or subjective experience that thoughts are racing, distractibility, increase in goal-directed activity or psychomotor agitation, excessive involvement in activities with a high potential for painful consequences.
- Depressive Episode:
- Depressed mood, loss of interest or pleasure in nearly all activities.
- Additional symptoms include significant weight change, sleep disturbances, psychomotor changes, fatigue, feelings of worthlessness or excessive guilt, diminished ability to think or concentrate, recurrent thoughts of death or suicide.
Pharmacology
- Mood Stabilizers:
- Lithium: Gold standard for treating and preventing both manic and depressive episodes; mechanism includes modulation of neurotransmitter signaling and neuroprotective effects.
- Anticonvulsants: Valproate and lamotrigine are commonly used for mood stabilization.
- Antipsychotics:
- Used during acute manic episodes and for maintenance in patients with severe episodes. Examples include olanzapine, risperidone, and quetiapine.
- Antidepressants:
- Used cautiously in bipolar disorder due to the risk of triggering manic episodes. Often prescribed in combination with a mood stabilizer.
High-Yield Points for Step 1
- Bipolar vs. Unipolar Depression: Understanding the distinguishing features and implications for treatment.
- Mechanisms of Mood Stabilizers: Key pharmacologic profiles of lithium, valproate, and lamotrigine.
- Genetic and Environmental Influences: Role of genetic predisposition and environmental triggers in the onset and progression of bipolar disorder.
- Neuroanatomy and Pathophysiology: Key brain structures involved in emotion regulation and their relevance to bipolar disorder.