F31.31 — Bipolar I Disorder, Current Episode Depressed, Mild

Clinical Description

F31.31 specifies bipolar I disorder where the current or most recent episode is a depressive episode of mild severity. Accurate coding requires documentation of at least one prior manic episode and the current depressive presentation.

Key Symptoms to Document

When using F31.31, your documentation should reference these symptoms:

• Depressed mood most of the day, nearly every day
• Diminished interest or pleasure in activities
• Fatigue or loss of energy
• Feelings of worthlessness
• Mild sleep disturbance (insomnia or hypersomnia)
• History of at least one manic episode

Common Interventions to Document

Evidence-based interventions typically documented with this diagnosis:

• Mood stabilizer pharmacotherapy (lithium, valproate, lamotrigine)
• Atypical antipsychotic augmentation (quetiapine, lurasidone)
• Interpersonal and Social Rhythm Therapy (IPSRT)
• CBT for bipolar disorder
• Psychoeducation on mood monitoring and early warning signs

CPT Code Pairings

Common CPT codes used when billing with F31.31:

• 90791 — Psychiatric diagnostic evaluation
• 90834 — Individual psychotherapy, 45 minutes
• 90837 — Individual psychotherapy, 60 minutes
• 99214 — Office visit, moderate complexity (medication management)
• 96127 — Brief emotional/behavioral assessment

Documentation Tips

• Document the history of at least one prior manic episode — this is what distinguishes bipolar I from MDD.
• Specify that the current episode is depressed and justify the mild severity rating (few symptoms beyond minimum, minor functional impairment).
• Note current medications, particularly mood stabilizers, and document rationale for avoiding antidepressant monotherapy.
• Record mood charting data or prospective mood tracking to support the bipolar pattern.
• Assess and document risk of mood switching, especially if antidepressants are being considered.

Differential Diagnosis Considerations

When documenting F31.31, consider and rule out:

• Major depressive disorder, single episode or recurrent (F32.x / F33.x)
• Bipolar II disorder, depressive episode (F31.81)
• Cyclothymic disorder (F34.0)
• Schizoaffective disorder (F25.x)
• Substance-induced mood disorder

Screening Tools

Standardized measures commonly used with this diagnosis:

• MDQ (Mood Disorder Questionnaire)
• PHQ-9 (for depressive symptoms)
• Young Mania Rating Scale (YMRS — to rule out mixed features)
• Altman Self-Rating Mania Scale (ASRM)
• Bipolar Spectrum Diagnostic Scale (BSDS)