I. GENERAL PRINCIPLES
A. Major depressive disorder is a psychiatric condition that affects mood and neurovegetative functions (e.g., sleep, appetite).
1. While experiencing a depressed mood transiently can be a normal and expected part of life, having the full constellation of symptoms meeting the criteria for major depressive disorder is never a normal or appropriate reaction to a stressful situation.
2. Left untreated, major depression increases rates of morbidity and mortality, especially from cardiac conditions.
B. Definition.
1. Major depressive disorder is a syndrome characterized by five or more of the symptoms listed in
Table 144-1 for 2 weeks or more.
2. One of the five symptoms must be either depressed mood or anhedonia (i.e., an absence of pleasure).
3. The mnemonic SIG: E CAPS (i.e., label: energy capsules) is a helpful guide to remember these defining criteria (
Table 144-1).
II. DIAGNOSIS
A. Clinical features. The manifestations of depression include affective, behavioral, and cognitive abnormalities (i.e., the ABCs of depression) (
Table 144-2). Though a depressed patient may be psychomotorically slowed and have scant facial expression, his or her sensorium will be intact. This helps to distinguish depression from delirium, in which the patient will have a reduced level of wakefulness, alertness, and/or attentiveness. The hypomanic or manic patient will have an elevated, expansive, or irritable mood rather than a dysphoric one.
B. Differential diagnosis. Depression in the intensive care unit (ICU) can occur as a primary affective disorder (e.g., major depressive disorder), a mood disorder associated with a specific medical condition or its treatment, or a psychological reaction to an acute medical illness.