12/15/2025
Coding Tip of the Week: Understanding “Code First” Rules in Behavioral Health
When coding behavioral health conditions, certain ICD-10-CM codes include a “code first” instruction. This means the underlying medical condition must be sequenced before the behavioral health manifestation.
Failing to follow this rule can lead to inaccurate risk capture, sequencing errors, and claim denials.
Why It Matters
“Code first” notes appear when the behavioral condition is caused by or is a manifestation of another illness. ICD-10-CM requires the etiology (cause) to be coded before the behavioral diagnosis.
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Common Behavioral Health Categories With “Code First” Requirements
1. Dementia in Other Diseases Classified Elsewhere (F02.80–F02.81x)
These codes are never used alone.
Sequence first: the underlying neurological or medical disease.
Example:
• G20.(XX) Parkinson’s disease
• F02.80 Dementia in other diseases classified elsewhere
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2. Mood Disorders Due to a Medical Condition (F06.31–F06.34)
These represent manifestation codes.
Example:
• I63.9 Cerebral infarction
• F06.31 Mood disorder due to known physiological condition with depressive features
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3. Psychotic Disorders Due to a Medical Condition (F06.2)
Used when psychosis results from an identified illness.
Example:
• E05.90 Hyperthyroidism
• F06.2 Psychotic disorder due to known physiological condition
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4. Anxiety Disorders Due to a Medical Condition (F06.4–F06.42)
Example:
• J44.9 COPD
• F06.4 Anxiety disorder due to known physiological condition
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5. Behavioral or Cognitive Changes Due to Physiological Conditions (F07.*)
Includes post-concussion syndrome, personality change after brain injury, and other cognitive disturbances.
Example:
• S06.2X9A Traumatic brain injury
• F07.81 Postconcussional syndrome
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Key Takeaway
If a behavioral health condition is secondary to another medical condition, check the Tabular List for a “code first” note.
Always code:
1. Underlying medical etiology
2. Behavioral/mental health manifestation
Proper sequencing ensures accurate clinical reporting and reimbursement.
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