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The subjective feelings known as emotions are an essential feature of normal
human experience; moreover, some of the most devastating psychiatric problems
involve emotional (affective) disorders. Although everyday emotions
are as varied as happiness, surprise, anger, feer, and sadness, some characteristics
are common to all of them. Thus, all emotions are expressed through
both physiological changes and stereotyped motor responses, especially of
the facial muscles. These responses accompany subjective experiences that
are not easily described, but which are much the same in all human cultures.
Expression of the emotions is closely tied to the
autonomic nervous system
and therefore entails the activity of certain brainstem nuclei, the hypothalamus,
and the amygdala, as well as the preganglionic neurons in the spinal
cord, the autonomic ganglia and peripheral effectors. The centers that coordinate
emotional responses have been grouped under the rubric of the limbic
system. At the cortical level, the two hemispheres differ in their governance
of the emotions, the right hemisphere being more critically involved
than the left - yet another example of hemispheric specialization.
AFFECTIVE DISORDERS
Whereas some degree of disordered emotion is present in virtually all psychiatric problems,
in affective (mood) disorders, the essence of the disease is an
abnormal regulation of the feelings of sadness and happiness that are part of
everyone's life. The most severe of these afflictions are major depression and
manic depression. (Manic depression is also called bipolar disorder, since such
pasients experience alternating episodes of depression and euphoria.) Depression,
the most common of the major psychiatric disorders, has a lifetime prevalence
of about 5 - 8% in the population; if one includes bipolar disorder, the lifetime
prevalence of affective disorders rises to nearly 10%! For clinical purposes, depression
(as distinct from bereavement or neurotic unhappiness) is defined by a set
of standard criteria, one or more of which must be present to tender the
diagnosis. In addition to an abnormal sense of sadness, despair, and bleak feelings
about the future (depression itself), these criteria include disordered eating
and weight control; disordered sleeping
(insomnia or hypersomnia); and diminished sexual interest.
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The overwhelming quality of major depression has been
compellingly described by pasient/authors such as William Styron, and by
afflicted psychologists such as Kay Jamison. But the depressed patient's profound sense of despair has been nowhere
better expressed than by Abraham Lincoln, who during a period of depression said:
"I am now the most miserable man living. If what I feel were equally distributed to
the whole human family, there would not be one cheerful face on earth. Whether I shall ever
be better, I cannot tell; I awfully forbode I shall not. To remain as I am is impossible.
I must die or be better, it appears to me."
Indeed, about half the suicides in this country occur in individuals with clinical
depression.
In earlier times, depression and mania were considered disorders that
arose from circumstances or the neurotic inability to cope with normal problems.
It is now universally accepted that these conditions are neurobiological disorders.
Among the strongest lines of evidence for this consensus are studies of the inheritance
of these diseases. For example, the concordance of affective disorders is
very high in monozygotic compared to dizygotic twins.
Despite evidence for a genetic pre disposition to affective disorders, the
cause remains unknown. The efficacy of a large number of drugs that influence
catecholaminergic and serotonergic neurotransmission strongly implies that the
basis of the disorder is ultimately neurochemical. The majority of patients (about
70%) can be effectively treated with one of a variety of drugs, which are among the most
widely prescribed agents worldwide.
Pharmaceutical companies have now succeeded in synthesizing drugs
that selectively block the uptake of serotonin without affecting the uptake of
other neurotransmitters.
Teksten er hentet fra boken "Neuroscience", Purves et al., 1997. Sinauer forlag
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