All ICD10 Codes
F09Billable, valid for claims from October 1, 2026

Unspecified mental disorder due to known physiological condition

In Mental disorders due to known physiological conditions (F01-F09), chapter 5: Mental, Behavioral and Neurodevelopmental Disorders

  • F09 is an unspecified code: use it only when the record doesn't document anything more specific. If the record has more detail, check the other codes under F01-F09 below.
  • As a secondary diagnosis it is not a CC or MCC, so it doesn't raise the MS-DRG payment.
  • Doesn't count toward a Medicare Advantage risk score (no HCC in V28).
  • AHRQ's Chronic Condition Indicator classes it as not chronic (an acute or short-term condition).

Also indexed as: Deficiency, cognitive; Disease, mental, organic; Disorder, cognitive; Disorder, cognitive, due to general medical condition; Disorder, mental, due to, brain disease, damage and dysfunction; Disorder, mental, due to, general medical condition; Disorder, mental, organic or symptomatic; Organic, brain syndrome; Organic, mental disorder; Organic, psychosis; Psychosis, organic; Psychosis, symptomatic; Syndrome, brain; Syndrome, brain, with psychosis, psychotic reaction; Syndrome, brain, organic; Syndrome, brain, organic, post-traumatic, psychotic; Syndrome, brain, psycho-organic; Syndrome, organic, brain

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Instructional notes

Includes: conditions that are coded here

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

Excludes1: not coded here, use a different code

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

Code first: code the underlying condition first, then this code

  • the underlying physiological condition

Official coding guidelines

From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.

Covers psychological pain disorders, substance use, abuse, dependence and remission, factitious disorder including Munchausen by proxy, and dementia severity.

Read Section I.C.5 (page 43)

Other codes under F01-F09

Mental disorders due to known physiological conditions (F01-F09)

F09 MS-DRGs

As the principal diagnosis, F09 groups to MS-DRG 884, 974, 975, or 976 (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.

Related conditions

Grouped by AHRQ's Clinical Classifications Software Refined (CCSR), which sorts every diagnosis code into clinically meaningful categories.

F09 is in Miscellaneous mental and behavioral disorders/conditions (MBD013, its default category), with 53 codes. Others in it:

  • F06.8 Other specified mental disorders due to known physiological condition
  • F07.9 Unspecified personality and behavioral disorder due to known physiological condition
  • F48.8 Other specified nonpsychotic mental disorders
  • F48.9 Nonpsychotic mental disorder, unspecified
  • F52.0 Hypoactive sexual desire disorder
  • F52.1 Sexual aversion disorder
  • F52.21 Male erectile disorder
  • F52.22 Female sexual arousal disorder

Medicare coverage articles listing F09

These 7 Medicare billing and coding articles list F09 as a diagnosis that supports medical necessity for the services they cover. From the CMS Medicare Coverage Database; check your own contractor's article before billing.

Other codes that refer to F09

Notes on these codes point to F09.

  • F29 Excludes1: unspecified mental disorder due to known physiological condition (F09)
  • F63.1 Excludes2: mental disorders due to known physiological condition (F01-F09)
  • F63.2 Excludes2: stealing in mental disorders due to known physiological condition (F01-F09)
  • F99 Excludes1: unspecified mental disorder due to known physiological condition (F09)
  • O99.34 Includes: Conditions in F01-F09, F20-F52 and F54-F99

About the condition

Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.

Mental Disorders

Mental disorders (or mental illnesses) are conditions that affect your thinking, feeling, mood, and behavior. They may happen over a short period of time or come and go. Some can be chronic (long-lasting). They can affect your ability to relate to others and function each day..

Read more about mental disorders on MedlinePlus

Code history

Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.

ICD-9-CM equivalent

Legacy crosswalk from the CMS General Equivalence Mappings (last updated 2018).

  • 310.9 Unspecified nonpsychotic mental disorder following organic brain damage (approximate)
ICD-9 to ICD-10 converter