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What is the cause of bipolar disorder?
 The
search for the cause of bipolar disorder made very little progress
over the first half of the 20th century. While there
continued to be various hypotheses as to the cause of bipolar
disorder, research did not seem to confirm their validity. For
example, psychodynamic theorists suggested that mania (similar to
depression) emerges from the loss of a loved object. They stated that
while some people introject the lost object and become depressed,
others deny the loss and become manic. In this explanation, in order
to avoid the terrifying conflicts generated by the loss, they escape
into it a dizzying round of activity. Controlled studies have not
found any systematic relationship between loss and the onset of a
manic episode, although some case reports have occasionally seemed to
fit somewhat with this explanation. More recently, biological
research has produced some much more promising clues of possible
causes of bipolar disorder including research into neurotransmitter
activity, sodium ion activity and genetic factors.
Neurotransmitters as a possible cause of bipolar disorder?
There has been
some suggestion that overactivity of the neurotransmitter
norepinephrine could be related to mania. This explanation was
suggested by several clinicians back in the 1960s when researchers
found a relationship between low norepinephrine activity and unipolar
depression. One research study found norepinephrine activity of
persons with mania to be higher than individuals with depression or
control subjects. The blood pressure medicine, Reserpine, was given
to patients in one study to reduce norepinephrine activity in the
brain and manic symptoms were said to have subsided.
Because there is often a parallel between
norepinephrine and serotonin activity in unipolar depression, some
theorists believed that mania may also be related to high serotonin
activity, but no relationship was able to be found. However, research
has found that mania like depression may be linked to low
serotonin activity. Researchers found for example, that the drug
lithium may actually increase brain serotonin activity. Lithium was
found to be and continues to be an effective treatment for bipolar
disorders. It is now believed that depression and mania both may be
related to low levels of serotonin.
In an effort to
somehow reconcile these somewhat contradictory findings, researchers
have proposed a “permissive theory” of mood disorders. They
now argue that low serotonin activity opens the door to mood disorder
and permits the activity of norepinephrine (or even possibly other
neurotransmitters) to define the actual form the disorder will take.
Low serotonin activity accompanied by a low norepinephrine activity
may lead to depression. Low serotonin activity accompanied by high
norepinephrine activity may lead to mania. These explanations seem to
be more in line with current beliefs about the cause of bipolar
disorder.
Subsequent pages
will also look at Ion activity and genetic factors as potential causes
of bipolar disorder.
Information from Abnormal Psychology Fourth Edition by Ronald
Comer
Additional information and
webpage by
Paul Susic MA Licensed Psychologist Ph.D Candidate (Health
Psychology
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