USMLE Step 1 · Psychiatry

Bipolar I disorder vs Bipolar II disorder and cyclothymic disorder

How to tell Bipolar I disorder and Bipolar II disorder and cyclothymic disorder apart when a board question makes them look alike.

Fastest separator

Mania equals bipolar I; hypomania plus major depression equals bipolar II; chronic subthreshold cycling equals cyclothymia.

Side by side

Bipolar I disorderBipolar II disorder and cyclothymic disorder

Key clue

Bipolar I is defined by at least one manic episode: elevated or irritable mood with increased energy, impaired function, hospitalization, or psychosis.

Bipolar II has hypomania plus major depression without mania; cyclothymic disorder has at least 2 years of subthreshold hypomanic and depressive symptoms.

Mechanism

Classification turns on episode severity: mania causes marked impairment, hospitalization, or psychosis and is enough for bipolar I.

Hypomania is noticeable but not severely impairing and has no psychosis; cyclothymia is chronic mood cycling below full episode thresholds.

Labs and tests

Decreased need for sleep, grandiosity, pressured speech, risky behavior, psychosis, or hospitalization supports mania and bipolar I.

Hypomanic episodes with major depression support bipolar II; many subthreshold mood swings over 2 years support cyclothymic disorder.

The trap

Do not diagnose bipolar II if there has ever been mania; mania automatically makes the diagnosis bipolar I.

Watch it explained

60-second lessonBipolar I vs Bipolar II vs Cyclothymia: Mania or Hypomania (USMLE Step 1)

Quiz yourselfBipolar I or II? 6-Second Psychiatry Pop Quiz (USMLE Step 1)

Test it now

The repair move

For bipolar disorders, decide whether the high-energy episode reached mania, hypomania, or only subthreshold cycling.

Try a free question

Core

A patient has 8 days of decreased need for sleep, grandiosity, pressured speech, risky spending, and hospitalization for unsafe behavior. Which diagnosis is most likely?

Show answer and explanation

Answer: A. Bipolar I disorder. A manic episode with hospitalization or marked impairment defines bipolar I disorder, even if depressive episodes are not described.

Why the other choices are tempting

B. Bipolar II requires hypomania and major depression without any manic episode.
C. Cyclothymic disorder has chronic subthreshold mood symptoms rather than a full manic episode.
D. Major depressive disorder does not include mania.
E. Persistent depressive disorder is chronic depressive mood without mania.

Flashcards

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What episode defines bipolar I disorder?

A manic episode defines bipolar I disorder.

What separates mania from hypomania?

Mania causes marked impairment, hospitalization, or psychosis; hypomania does not.

Quick answers

What is the fastest way to tell Bipolar I disorder from Bipolar II disorder and cyclothymic disorder?