Alphabetic Index FY2027

F09

Unspecified mental disorder due to known physiological condition

FY2027Chapter 5: Mental, Behavioral and Neurodevelopmental disorders/F01–F09 Mental disorders due to known physiological conditions

BillableComplete code, valid to report
Care settingsHospice: not accepted as primaryIPF Primary · MS-DRG 884

F09 is a billable ICD-10-CM diagnosis code for unspecified mental disorder due to known physiological condition. It is part of the FY2027 code set, effective October 1, 2026. The Alphabetic Index lists it under 18 entries. Its coding notes include a Code first instruction, 2 Excludes1 entries and 1 Excludes2 entry.

Code first

If the underlying condition listed here is present and known, sequence it first.

This code
  • the underlying physiological condition

Excludes1

Not coded here. The listed conditions generally should not be reported together.

This code
  • mild neurocognitive disorder due to known physiological condition (F06.7-)
  • psychosis NOS (F29)

Excludes2

Not included here. Both codes may be reported if the patient has both conditions.

Also from chapter/block level (1 note)
Inherited from Chapter 5 Mental, Behavioral and Neurodevelopmental disorders
  • symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)

Care settings

How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.

Hospice: not accepted as primary

Not accepted as the principal diagnosis on a hospice claim (bill types 081x and 082x). The Integrated OCE returns an edit for this code.
Reason: Supplementary or additional code, not allowed as principal diagnosis.

Source: CMS Integrated Outpatient Code Editor (IOCE) v27.3, effective October 1, 2026, edit 113

IPF Primary

IPF MS-DRG adjustment. A principal diagnosis of this code groups to this MS-DRG:

MS-DRGDescriptionFactor
884Organic disturbances & intellectual disabilities1.08
A principal diagnosis that groups to none of the 19 designated MS-DRGs gets no MS-DRG adjustment. Otherwise the claim still receives the federal per diem base rate and the other adjustments.

Source: CMS IPF PPS FY 2027 final rule (CMS-1847-F), Addendum A; code lists from the CMS MS-DRG Definitions Manual v44; effective for discharges on or after October 1, 2026

Includes

Further defines or gives examples of the content of the category.

Also from chapter/block level (1 note)
Inherited from Chapter 5 Mental, Behavioral and Neurodevelopmental disorders
  • disorders of psychological development

Inclusion terms

Conditions classified to this code.

This code
  • Mental disorder NOS due to known physiological condition
  • Organic brain syndrome NOS
  • Organic mental disorder NOS
  • Organic psychosis NOS
  • Symptomatic psychosis NOS

Notes

Also from chapter/block level (1 note)
Inherited from F01–F09 Mental disorders due to known physiological conditions
  • This block comprises a range of mental disorders grouped together on the basis of their having in common a demonstrable etiology in cerebral disease, brain injury, or other insult leading to cerebral dysfunction. The dysfunction may be primary, as in diseases, injuries, and insults that affect the brain directly and selectively; or secondary, as in systemic diseases and disorders that attack the brain only as one of the multiple organs or systems of the body that are involved.

Alphabetic Index terms

Terms the official Alphabetic Index lists for this code. 18 entries

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