Depression should be classified by episode, severity, and state of remission.

Depression is estimated to affect nearly 17 million adults in the U.S., but this is probably an underestimate of the true rate. Women are diagnosed with depression much more often than men, so underestimation is particularly likely for the latter.

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Image by Getty Images

Depression rates tend to decrease with increasing age, especially over 65 years. Again, though, the condition could be underdiagnosed as symptoms may differ between the young and the old. In older patients, manifestations may be subtle. Patients who are chronically ill, have dementia, or live in chronic care facilities are quite likely to become depressed. Depression can be due to an underlying medical condition or to a treatment, notably hypercortisolism (Cushing's disease), long-term steroid therapy, beta-blockers, or interferon.

Accurately diagnosing, documenting, and coding depression have a significant impact on diagnosis-related group assignment and quality reporting, and it only takes a basic understanding to become relatively proficient. When depression appears likely, a mental health consult may be in order to assist with accurate diagnosis and treatment, since symptoms of depression occur commonly in other mental health disorders, especially bipolar disorders.

The diagnostic standards for depression are defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). The various types of depression described by DSM-5, major depressive disorder (MDD) being by far the most commonly encountered, are listed in Table 1, together with corresponding ICD-10-CM codes and comorbidity/complication (CC) status.

According to DSM-5, MDD is diagnosed by the presence of all of the following: five or more cardinal symptoms (one must be depressed mood or loss of interest or pleasure in activities) during the same two-week period representing a change from baseline function (see Table 2); no history of mania or hypomania; symptoms that cause significant distress or impairment; and symptoms that are not attributable to the effects of substance abuse, a psychosis like schizophrenia, or an underlying medical condition.

MDD is further classified by episode (single vs. recurrent), severity (mild, moderate, severe, or with psychotic features), and state of remission (partial, full, or not in remission). A single episode is simply the first occurrence of MDD symptoms; all subsequent episodes are considered “recurrent” (the vast majority of cases).

MDD is classified in categories F32 (single episode) and F33 (recurrent episode). Single-episode codes F32.0 to F32.3, which describe severity, have CC status, affecting revenue and quality metrics. Therefore, when a patient is admitted with the first-ever episode, it's necessary to document it as a single episode of MDD and specify the severity. If any state of remission is mentioned, it will not be a CC. All cases of MDD documented as “recurrent” are classified as CCs except when specified as full or partial remission. Otherwise recurrent MDD not specified as “in remission” will be assigned a CC code (F33.40). Documentation of MDD alone without further specification is coded as F32.9 (non-CC). Documentation of recurrent (with or without severity) or single episode plus severity is necessary for CC status. State of remission does not have to be documented.

The patient in full remission is one who has had no significant signs or symptoms for over two months following an MDD episode. Partial remission describes a patient who has persistent symptoms that no longer meet the full criteria or who has gone less than two months without significant symptoms following an episode.

Severity is determined by the clinician's professional assessment of the intensity of symptoms and degree of functional impairment. Mild cases demonstrate only a few symptoms with distressing but manageable intensity and minor functional impairment. Severe MDD is associated with a large number of symptoms, especially suicidal thoughts or intention or deep withdrawal, intense and unmanageable symptoms, and marked functional impairment. In moderate MDD, symptoms are intermediate between mild and severe. Psychotic features are recognized by delusions and/or hallucinations.

MDD must be distinguished from bipolar I and II. The diagnosis of bipolar I (category F31) requires both fulfillment of MDD criteria and a current or previous manic episode. Mania is described as a distinct period of persistently elevated, expansive, irritable mood, causing marked impairment of social/occupational function, necessitating hospitalization, or exhibiting psychotic features.

The diagnosis of bipolar II (code F31.81) is essentially the same as bipolar I except only a hypomanic episode has occurred, manifested by an uncharacteristic change in function not requiring hospitalization or exhibiting psychotic features.

Almost every code for any description of bipolar I and II, or for isolated manic episodes that don't meet MDD criteria (category F30), has CC status unless in any way stated as “in remission.” The code assigned for an unspecified type of bipolar disorder (F31.9) and for a hypomanic episode alone that doesn't meet MDD criteria (F30.8) are non-CCs. Therefore, always identify the type of bipolar disorder.