As remarked in Chap. 23, the term depression embraces more than a feeling of sadness and unhappiness. It stands for a complex of disturbed feelings (called mood or affective disorder)—which may include aspects of despair, hopelessness, sense of worthlessness, and thoughts of self-harm—associated with decreased energy and libido, loss of interest in personal affairs, impaired concentration, various abnormalities of behavior and appearance, and sometimes, prominent physical complaints. The most important of these include anxiety, insomnia, anorexia or overeating, headache, and various types of regional pain. At one extreme are depressive symptoms of psychotic proportions that incorporate paranoid or somatic delusions, which create chaos in the lives of patients and those close to them. At the other extreme are the common feelings of unhappiness, anhedonia (loss of pleasurable responses), discouragement, and resentment that may occur in almost everyone as a reaction to the disappointments of everyday life such as loss of employment, failure to gain recognition, or unsuccessful social adjustment.
The place in this nosology of the special case of postpartum depression has not been clear, and it is discussed in this chapter as well in the next one, as it is sometimes difficult to differentiate it from postpartum psychosis, a more dramatic and well-defined disorder. Some authors question the primacy of a primary biologic entity that is tied to the postpartum period (see summary by Brockington) but this diverges markedly from the general experience, in which varying degrees of depression are quite common in the weeks after delivery and cannot simply be attributed to psychosocial factors or sleep deprivation.
As a purely phenomenological observation, an abnormally elevated mood, or mania, is about one-third as frequent as depression. It may develop as a relatively pure, recurrent clinical state, or more often may alternate or be intertwined with depression, in which case it was referred to as manic-depressive disease (now, bipolar disorder in the classification of the Diagnostic and Statistical Manual of Mental Disorders (see under American Psychiatric Association in references). Hypomania and cyclothymic disorder are the names given to milder forms of mania and bipolar disorder, respectively. The DSM classifications also acknowledge the existence of a mixed schizoaffective state in which attributes of depression and schizophrenia are combined. Distinguishing these various types of depressive illnesses is of therapeutic as well as theoretical importance insofar as a particular type may respond better to one form of treatment than to another. Finally, the neurologist should bear in mind the possibility of an incipient dementia presenting as a depression, although the reverse, a masked depression causing difficulty with thinking and memory (pseudodementia) is more common in general practice.
Patients reacting to a medical or neurologic illness seldom express feelings of sadness or despair without mentioning physical accompaniments such as easy fatigability, anxiety, headaches, dizziness, loss of appetite, reduced interest in life and love, trouble in falling asleep, or premature awakening. It follows that whenever these symptoms become manifest in the course of medical disease, they should arouse suspicion of a depressive reaction (Table 48-1).
Chronic pain is a frequent somatic manifestation of depression. The pain may be based on an attendant disease but is prolonged, disabling, sometimes vague in nature, and recalcitrant to straightforward medical and surgical approaches. Furthermore, depressed mood exacerbates and prolongs pain of any type. All patients with chronic pain syndromes should be evaluated psychiatrically, as pointed out in Chap. 7.