Depression Due to Medical Condition: ICD-10

Depression caused by a physiological condition — hypothyroidism, stroke, Parkinson’s disease, traumatic brain injury — does not code to the F32/F33 major depressive disorder family. It codes to the F06.3 family (“mood disorder due to known physiological condition”), and it comes with a mandatory sequencing rule that trips coders constantly: the underlying medical condition is coded first. This guide maps the family as published in the FY2026 ICD-10-CM tabular list ↗, works through the sequencing, and draws the three-way differential against primary mood disorders and adjustment disorders.

This page is part of our ICD-10 directory for behavioral health; for the primary mood-disorder block, see the F30–F39 guide.

The F06.3 family table

F06.3 sits in the F01–F09 block — “Mental disorders due to known physiological conditions.” All titles below are verified against the FY2026 tabular.

Note the F06.3 category’s Excludes2 boundaries: mood disorders due to alcohol and other psychoactive substances belong in the F10–F19 structure (the.14/.24/.94 character patterns — see the substance family pages ), and mood disorders not due to a known physiological condition belong in F30–F39.

The F06.31 vs. F06.32 line is the family’s everyday decision, and it is a symptom-threshold question: features vs. full episode. The note should say which — “depressive symptoms not meeting full episode criteria” or “meets criteria for a major depressive-like episode” — because the code asserts it either way.

Sequencing: code the underlying condition first

The F06 category carries the instructional note “code first the underlying physiological condition” in the FY2026 tabular. Code-first notes are not suggestions — they are sequencing instructions, and claims that ignore them are coded incorrectly even when both codes are present.

A correct claim is therefore a two-code minimum, medical condition first:

(Examples are illustrative; code the specific condition the provider documents — e.g., a thyroid disorder more specific than E03.9 when established.)

Two operational notes for behavioral health settings:

• The medical code must come from somewhere. A BH facility’s clinicians often are not the ones managing the endocrine or neurological condition. The intake and coordination-of-care workflow needs to capture the documented medical diagnosis — from referral records or the treating physician — so the claim can carry it first-listed. “Depression due to hypothyroidism” with no thyroid code on the claim is an incomplete claim.
• First-listed ≠ primary focus of treatment. Sequencing E03.9 ahead of F06.31 does not mean the encounter was about thyroid management. The F06.3x code still tells the payer what the behavioral health service treated.

F06.3x vs. primary MDD vs. adjustment disorder

Three mechanisms, three code families. The decision logic:

The hard case is the medically ill patient who is depressed. Due to the condition (physiological mechanism → F06.31/.32) is different from upset about the condition (psychological reaction → F43.21) and from independent of the condition (primary MDD → F32/F33). The differential turns on mechanism and course: did the mood disturbance track the onset or exacerbation of the medical condition? Does it respond to treating the underlying condition? Is there a prior psychiatric history that better explains it? DSM-5-TR frames the F06-equivalent diagnosis as requiring evidence from history, examination, or laboratory findings that the disturbance is the direct pathophysiological consequence of the condition — a standard described here in original words.

Getting this wrong has real consequences in both directions: coding F32.x for an untreated-hypothyroid depression buries the reversible cause; coding F06.32 on clinician hunch without a documented causal link is unsupportable in audit.

Documentation requirements

The F06.3x codes assert causation, so the documentation must establish it:

For facilities treating medically complex clients, this is fundamentally a records-coordination problem: external medical documentation, internal psychiatric assessment, and the claim have to agree. ’s EHR supports multi-diagnosis problem lists and documentation workflows built for behavioral health teams coordinating with outside medical providers.

• Explicit causal language. “Depression due to hypothyroidism,” “mood disorder secondary to CVA” — the linkage must be stated by the diagnosing provider, not assembled by the coder from a problem list that happens to contain both conditions. If the chart shows depression and a medical condition without a stated link, the compliant route is a provider query.
• Who establishes causation. The clinical judgment belongs to the diagnosing clinician — typically the psychiatrist or psychiatric NP in a BH setting, ideally corroborated by the treating medical provider’s records. Document the basis: temporal course, known association, lab findings, response to medical treatment.
• The medical record trail. Keep the referral records, labs, or consult notes that document the underlying condition in the chart. The first-listed medical code on the claim needs support in your record, not just in another provider’s.
• Reassessment over time. If the depressive syndrome persists after the underlying condition is controlled, the diagnosis deserves review — it may declare itself as a primary mood disorder, and the code should follow. Build that review into treatment plan updates.

Billing notes

Request a Demo of diagnosis-to-claim workflows built for behavioral health: contact us.

• Benefit routing. F06.3x claims sit at the medical/behavioral boundary, and payers differ on whether they adjudicate under the behavioral health benefit (by the F-code and service type) or flag for the medical benefit (by the first-listed condition). Expect more routing friction than with F32/F33 claims, and confirm benefit handling at verification for clients carrying F06.3x diagnoses.
• UR framing. For utilization review, the F06.3x code plus its underlying condition is a strength, not a complication: it documents medical complexity that supports care-coordination intensity and, where applicable, a medically monitored level of care. State both conditions and the management plan for each in continued-stay submissions.
• Watch the denial pattern. Sequencing errors (F06.3x first-listed where the payer enforces the code-first note) produce a distinctive, fixable denial cluster — track it in your revenue cycle reporting. Psychiatric evaluation of these presentations is billed under 90791 like any other diagnostic workup.

Sources: FY2026 ICD-10-CM code set and tabular list ↗ (CMS, effective Oct 1, 2025), F06 category notes including the code-first instruction; ICD-10-CM Official Guidelines for Coding and Reporting, FY2026 ↗; CDC NCHS ICD-10-CM ↗. Accessed June 2026.

Reference tables

Common questions

Official sources

• FY2026 ICD-10-CM tabular listcms.gov
• ICD-10-CM Official Guidelines for Coding and Reporting, FY2026cms.gov
• CDC NCHS ICD-10-CMcdc.gov