Clinical Description Page 1

I copied the section about manic-depression from A MERCK manual, 1979.  It has a good clinical description of Depression, and Manic-depression.

(Manic-Depressive Reaction or Psychosis)

Manic-depressive illnesses are characterized by pathologic mood changes (elation or sadness), spontaneous recoveries, and a tendency to recur.  Two genetically independent forms of the illness have now been defined: bipolar (cycles of mania and depression) and unipolar (recurrent depression).
Incidence and Etiology
The overall incidence of manic-depressive illness is I to 2% and is twice as great in women as in men.  The incidence is high among higher socioeconomic groups.  The illness may begin any time from adolescence to old age, but the peak onset is at 30 yr of age for the bipolar states and 50 yr for the unipolar states.  Manic-depressive disorders are most likely to develop in the late spring.  Most newly disposed patients have been relatively stable, but they have experienced mild cyclothymic swings in the past. .
Hereditary factors are important, and 10 to 15% of first-degree relatives (parents, siblings, and children) of patients with bipolar illness will also suffer from the disorder.  The bipolar form is probably transmitted by
a dominant gene and the unipolar by a polygenic system.  Cultural and familial influences, such as the loss of a parent in childhood, also play an important part in predisposing to the two conditions, particularly the unipolar form.
The mood changes, whether depression or mania, usually develop for no clear external reason, though occasionally psychologic or physical stress may have preceded the illness.  Biochemical changes accompany the mood changes, and in both mania and depression there is evidence of an increased concentration of intracellular sodium that returns to normal following recovery.  More importantly in depression, cerebral monoamines in the hypothalamus and brainstem are depleted; these changes may be causative.

Symptoms and Signs

Depressive phase (manic-depressive, psychotic, or endogenous depression; Involutional melancholia): The illness has a rapid onset and swift progression.  Loss of self-esteem and a feeling of despondency, often described by the patient as different from normal unhappiness, are the characteristic central features.  However, occasionally the patient may  describe only a sense of emotional emptiness, apathy, or inertia and may even deny feeling depressed.

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