What are the diagnostic criteria for bipolar 2 disorder?

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, with no history of manic or mixed episodes. 1, 2

Hypomanic Episode Criteria

A hypomanic episode requires:

• Duration of at least 4 days 1, 3
• Elevated (euphoric) and/or irritable mood
• At least 3 of the following symptoms (4 if mood is only irritable):
  • Grandiosity or inflated self-esteem
  • Decreased need for sleep without feeling tired
  • More talkative than usual or pressure to keep talking
  • Racing thoughts or flight of ideas
  • Distractibility
  • Increased goal-directed activity or psychomotor agitation
  • Excessive involvement in pleasurable activities with high potential for painful consequences 1, 3
• Observable change in functioning that is uncharacteristic of the person
• Not severe enough to cause marked impairment in social or occupational functioning
• Does not require hospitalization
• No psychotic features 3

Depressive Episode Criteria

A major depressive episode requires:

• At least 5 of the following symptoms present during the same 2-week period, representing a change from previous functioning (at least one symptom must be depressed mood or loss of interest/pleasure):
  • Depressed mood most of the day, nearly every day
  • Markedly diminished interest or pleasure in almost all activities
  • Significant weight loss/gain or change in appetite
  • Insomnia or hypersomnia
  • Psychomotor agitation or retardation
  • Fatigue or loss of energy
  • Feelings of worthlessness or excessive guilt
  • Diminished ability to think or concentrate
  • Recurrent thoughts of death or suicidal ideation 1

Key Diagnostic Features and Distinctions

• The primary distinction between Bipolar I and Bipolar II is the absence of full manic episodes in Bipolar II 1, 3
• Depressive episodes typically outnumber hypomanic episodes by a ratio of 39:1 in Bipolar II disorder 4
• Bipolar II depression is often the predominant feature and usually what leads patients to seek treatment 3
• Bipolar II depression may frequently present as "mixed depression" with concurrent subsyndromal hypomanic symptoms 3, 5

Diagnostic Challenges

• Bipolar II disorder is frequently underdiagnosed or misdiagnosed as unipolar depression 3, 4
• Recent epidemiological studies suggest a lifetime community prevalence of around 5% for Bipolar II disorder, much higher than the 0.5% reported in DSM-IV 3
• In depressed outpatients, as many as one in two may have Bipolar II disorder 3
• The combination of racing thoughts, irritability, and distractibility during a depressive episode has high sensitivity (76.8%) for predicting Bipolar II diagnosis 5
• The presence of 3 or more hypomanic symptoms during a depressive episode (DMX3) has high specificity (86.7%) for Bipolar II diagnosis 5

Clinical Implications

• Early and accurate diagnosis is crucial for proper management 6
• Despite being often perceived as less severe than Bipolar I, evidence suggests significant functional and cognitive impairment in Bipolar II 4
• Bipolar II carries an elevated risk of suicidal behavior, with completed suicide rates at least equivalent to those in Bipolar I disorder 4
• Psychiatric comorbidities, particularly anxiety and substance use disorders, are common 4
• Cardiovascular diseases and other physical comorbidities occur at higher rates in Bipolar II patients 4

Clinicians should maintain a high index of suspicion for Bipolar II disorder when evaluating patients with recurrent depressive episodes, particularly when there is a family history of bipolar disorder, early onset of depression, antidepressant-induced hypomania, or atypical depressive features.