Diagnostic Criteria for Bipolar II Disorder
Bipolar II disorder is defined by the occurrence of at least one hypomanic episode and at least one depressive episode. 1 This clear diagnostic definition is recognized in both the ICD-11 and DSM-5 classification systems as a distinct subtype of bipolar disorder.
Core Diagnostic Features
Hypomanic Episode Requirements
- Requires elevated (euphoric) and/or irritable mood
- Plus at least 3 of the following symptoms (4 if mood is only irritable):
- Grandiosity
- Decreased need for sleep
- Increased talking
- Racing thoughts
- Distractibility
- Overactivity (increase in goal-directed activity)
- Psychomotor agitation
- Excessive involvement in risky activities 2
- Duration requirement: At least 4 days according to DSM criteria 2
- Must represent a marked departure from baseline functioning and be evident across different settings 3
- Must NOT be severe enough to cause marked impairment in social or occupational functioning or require hospitalization 2
Depressive Episode Requirements
- Must meet criteria for a major depressive episode
- Patients with Bipolar II often present with recurrent depressive episodes, which significantly outnumber hypomanic episodes by a ratio of approximately 39:1 4
Key Diagnostic Distinctions
Bipolar I vs. Bipolar II
The primary distinction between Bipolar I and Bipolar II disorders is:
- Bipolar I: Presence of at least one manic episode (which may include psychotic features and causes marked impairment)
- Bipolar II: Presence of hypomanic episodes only (no history of mania) 4
Common Diagnostic Challenges
- Bipolar II is frequently misdiagnosed as major depressive disorder due to the prominence of depressive episodes 4
- Patients often present during depressive episodes and may not report past hypomanic episodes unless specifically questioned 5
- Clinicians should not rule out bipolar disorder simply because a patient lacks a history of depressive episodes 3
- Hypomanic episodes may be associated with increased functioning, making patients less likely to report them as problematic 2
Clinical Presentation Considerations
- Bipolar II often presents with mixed depression (depression with concurrent subsyndromal hypomanic symptoms) 2
- Family history of mood disorders is important to assess, with early-onset cases being predominantly male 3
- Common premorbid conditions include disruptive behavior disorders and anxiety 3
- Significant overlap of symptoms with other disorders, particularly borderline personality disorder, can complicate diagnosis 4
Important Diagnostic Pitfalls to Avoid
- Failure to screen for past hypomanic episodes in patients presenting with depression is the most common reason for misdiagnosis
- Overlooking brief hypomanic episodes that don't meet the full 4-day duration requirement but may still indicate bipolar spectrum disorder
- Focusing only on mood changes rather than also assessing for increased goal-directed activity, which is a core feature of hypomania 4
- Assuming Bipolar II is less severe than Bipolar I - evidence suggests significant functional and cognitive impairment with elevated suicide risk in Bipolar II 4
- Treating with antidepressant monotherapy without mood stabilizers, which may worsen the course of illness 4
Early and accurate diagnosis is crucial for appropriate treatment selection and improved outcomes in patients with Bipolar II disorder.