Definition and Core Features

• Bipolar disorder is a mood disorder characterized by episodes of mania, hypomania, and major depression.
• There are a few types; the most clinically distinct are Bipolar I and Bipolar II.

Bipolar I vs Bipolar II

• Bipolar I: defined by at least one manic episode; often accompanied by depressive or hypomanic periods.
• Bipolar II: defined by at least one hypomanic episode and at least one major depressive episode; there are no manic episodes.
• Mixed episodes: depressed mood coexists with manic symptoms; patients meet criteria for both depressive and manic episodes at the same time.
• Rapid cycling: alternating periods of hypomanic periods with mild to moderate depressive symptoms intermingled over the course of two years.

Epidemiology and Onset

• Lifetime prevalence worldwide: $1\% \text{ to } 3\%$.
• Mean age of onset: Bipolar I $\approx 18\ \text{years}$; Bipolar II $\approx 20\ \text{years}$.
• Gender distribution: equal prevalence, ratio 1:1.
• Presentation: patients will often present first in their primary care settings, not to the psychiatrist.

Recurrence and Prognosis

• Quiz: What percentage of individuals with a history of one manic episode will go on to have another manic episode? Answer: $90\%$ in the absence of treatment.
• Unmanaged illness has a very high recurrence rate.
• Sleep disruption increases mania risk: when sleep becomes imbalanced due to travel, time zone changes, or night shifts, mania risk rises.

Underdiagnosis and Misdiagnosis

• Bipolar disorder tends to be underdiagnosed and is often misdiagnosed, especially in ethnic minorities as schizophrenia.

Differential Diagnosis: Medical Mimics

• Before labeling bipolar disorder, rule out medical conditions that can mimic mood symptoms:
  • Neurological: epilepsy or seizures (especially temporal lobe), multiple sclerosis, viral encephalitis, cerebral tumors
  • Metabolic: hypothyroidism, Cushing\'s syndrome, neoplasms, HIV infection, B12 deficiency
  • Systemic: uremia, carcinoid syndrome

Substance- and Medication-Induced Mimics

• Substances or medications that can mimic bipolar disorder include:
  • Steroids; sympathomimetics; bronchodilators (common asthma medications); Levodopa; antidepressants
  • Antidepressants can unmask a manic episode in susceptible individuals
  • Any agent that increases dopamine and alpha-adrenergic activity can mimic bipolar

Euthymia vs Bipolar States

• Euthymia: a steady, baseline mood with typical ups and downs.
• In bipolar disorder, the highs become very high and the lows very low.
• Bipolar I: mania is prominent; Bipolar II: hypomania with more depressive episodes
• Cyclothymia: rapid mood shifts within a two-year period

Visual Aids and Context

• A chart exists that maps the various bipolar subtypes to their typical mood episodes to provide a visual context when studying.