What are the diagnostic criteria and treatment options for bipolar 2 disorder?

Diagnostic Criteria for Bipolar II Disorder

Bipolar II disorder requires at least one major depressive episode and at least one hypomanic episode lasting a minimum of 4 days, with no history of full manic or mixed episodes. 1, 2, 3

Core Diagnostic Requirements

Hypomanic Episode Criteria

• A distinct period of abnormally elevated, expansive, or irritable mood lasting at least 4 consecutive days, representing a clear departure from baseline functioning 1, 2
• Must include at least three of the following symptoms (four if mood is only irritable): grandiosity, decreased need for sleep without fatigue, increased talking/pressured speech, racing thoughts, distractibility, increased goal-directed activity, and excessive involvement in risky pleasurable activities 2
• The key distinction from mania: hypomania does NOT cause marked impairment in social or occupational functioning and does NOT require hospitalization 1, 2
• Hypomania often actually increases functioning, which helps distinguish it from mania 2

Major Depressive Episode Criteria

• Bipolar II depression is the dominant feature and most common reason patients seek treatment 2, 3
• Depressive episodes often present with psychomotor retardation and hypersomnia (excessive sleep), distinguishing them from manic states where sleep need dramatically decreases 1, 4
• Depression in bipolar II may be "mixed depression" with concurrent subsyndromal hypomanic symptoms 2
• Patients with bipolar II experience depressive episodes that outnumber hypomanic episodes by a ratio of 39:1 3

Critical Diagnostic Challenges

Underdiagnosis and Misdiagnosis

• Bipolar II is frequently misdiagnosed as unipolar major depressive disorder because patients typically present during depressive episodes and may not recognize or report past hypomanic periods 5, 2, 3
• While DSM-IV reported a lifetime prevalence of 0.5%, epidemiological studies find the actual prevalence (including bipolar spectrum) is around 5% 2
• In depressed outpatients, one in two may actually have bipolar II disorder 2

Essential Assessment Approach

• A longitudinal life chart documenting mood patterns over time is essential, not just a cross-sectional assessment 1
• Map the exact duration of activated states, changes in sleep patterns (particularly decreased need for sleep), and functional changes across multiple settings 1
• Key diagnostic questions: Are there distinct periods representing significant departure from baseline? Does the patient experience decreased need for sleep (not just insomnia) during elevated mood? Do mood changes occur spontaneously or only reactively to stressors? 1

Common Diagnostic Pitfalls

• Brief mood swings lasting minutes to hours do NOT meet criteria for hypomania, which requires at least 4 days duration 1
• Chronic baseline irritability and emotional dysregulation without distinct episodes departing from baseline do not constitute hypomania 1
• Mood changes that are purely reactive to stress or interpersonal conflict rather than spontaneous do not meet hypomania criteria 1
• Patients with mood dysregulation are often misdiagnosed as bipolar II when they may have borderline personality disorder, especially in youth 1, 3

Special Considerations

Rapid Cycling Pattern

• Rapid cycling is defined as four or more distinct mood episodes within 12 months, with each episode still meeting full duration criteria (4 days for hypomania, 7 days for mania) 1, 6
• This is a course specifier, not a separate diagnosis, and can occur in both bipolar I and II 6
• More common in youth, where mood shifts may be more labile and erratic 1, 6

Psychotic Features

• If psychotic features are present, they should occur primarily during mood episodes, not between episodes 1
• Document the temporal relationship between mood symptoms and any psychotic features 1

Comorbidities

• High rates of comorbid anxiety disorders, substance use disorders, and ADHD must be evaluated 1, 3, 7
• Elevated suicide risk equivalent to bipolar I disorder requires careful assessment 3, 7

Treatment Implications

Acute Hypomania

• Treat hypomania even if associated with increased functioning, because depression typically follows the hypomania-depression cycle 2
• Mood stabilizers (lithium, valproate) and second-generation antipsychotics (quetiapine, olanzapine, risperidone, aripiprazole) are indicated 8, 2

Acute Depression

• Antidepressant monotherapy may worsen prognosis and should be avoided 3
• Quetiapine has demonstrated efficacy in controlled trials for bipolar II depression 5, 2
• If antidepressants are used, they must be combined with a mood stabilizer, as monotherapy may destabilize mood or precipitate hypomania 8

Maintenance Treatment

• Lithium is supported by multiple controlled studies for preventing both depressive and hypomanic recurrences 5, 2
• Lamotrigine has shown efficacy in delaying depression recurrences 5, 2, 9
• Ongoing monitoring is essential as mood episode relapses are common despite treatment 7