A separate diagnosis of Mood Disorder Due to a General Medical Condition is not given if the mood disturbance occurs exclusively during the course of a delirium. In contrast, a diagnosis of Mood Disorder Due to a General Medical Condition may be given in addition to a diagnosis of dementia if the mood symptoms are a direct etiological consequence of the pathological process causing the dementia and if the mood symptoms are a prominent part of the clinical presentation (e.g., Mood Disorder Due to Alzheimer’s Disease). Because of ICD-9-CM coding requirements, an exception to this is when depressive symptoms occur exclusively during the course of Vascular Dementia. In this case, only a diagnosis of Vascular Dementia with the subtype With Depressed Mood is given; a separate diagnosis of Mood Disorder Due to a General Medical Condition is not made. If the presentation includes a mix of different types of symptoms (e.g., mood and anxiety), the specific mental disorder due to a general medical condition depends on which symptoms predominate in the clinical picture.
If there is evidence of recent or prolonged substance use (including medications with psychoactive effects), withdrawal from a substance, or exposure to a toxin, a Substance-Induced Mood Disorder should be considered. It may be useful to obtain a urine or blood drug screen or other appropriate laboratory evaluation. Symptoms that occur during or shortly after (i.e., within 4 weeks of) Substance Intoxication or Withdrawal or after medication use may be especially indicative of a Substance-Induced Disorder, depending on the character, duration, or amount of the substance used. If the clinician has ascertained that the disturbance is due to both a general medical condition and substance use, both diagnoses (i.e., Mood Disorder Due to a General Medical Condition and Substance-Induced Mood Disorder) are given.
Mood Disorder Due to a General Medical Condition must be distinguished from Major Depressive Disorder, Bipolar I Disorder, Bipolar II Disorder, and Adjustment Disorder With Depressed Mood (e.g., a maladaptive response to the stress of having a general medical condition). In Major Depressive, Bipolar, and Adjustment Disorders, no specific and direct causative physiological mechanisms associated with a general medical condition can be demonstrated. It is often difficult to determine whether certain symptoms (e.g., weight loss, insomnia, fatigue) represent a mood disturbance or are a direct manifestation of a general medical condition (e.g., cancer, stroke, myocardial infarction, diabetes). Such symptoms count toward a diagnosis of a Major Depressive Episode except in cases where they are clearly and fully accounted for by a general medical condition. If the clinician cannot determine whether the mood disturbance is primary, substance induced, or due to a general medical condition, Mood Disorder Not Otherwise Specified may be diagnosed.