Some types of
depression run in families, suggesting that a biological vulnerability
can be inherited. This seems to be the case with bipolar disorder.
Studies of families in which members of each generation develop
bipolar disorder found that those with the illness have a somewhat
different genetic makeup than those who do not get ill. However,
the reverse is not true: Not everybody with the genetic makeup
that causes vulnerability to bipolar disorder will have the
illness. Apparently additional factors, possibly stresses at
home, work, or school, are involved in its onset.
In some families, major depression also seems to occur generation
after generation. However, it can also occur in people who have
no family history of depression. Whether inherited or not, major
depressive disorder is often associated with changes in brain
structures or brain function.
People who have low self-esteem, who consistently view themselves
and the world with pessimism or who are readily overwhelmed
by stress, are prone to depression. Whether this represents
a psychological predisposition or an early form of the illness
is not clear.
In recent years, researchers have shown that physical changes
in the body can be accompanied by mental changes as well. Medical
illnesses such as stroke, a heart attack, cancer, Parkinson's
disease, and hormonal disorders can cause depressive illness,
making the sick person apathetic and unwilling to care for his
or her physical needs, thus prolonging the recovery period.
Also, a serious loss, difficult relationship, financial problem,
or any stressful (unwelcome or even desired) change in life
patterns can trigger a depressive episode. Very often, a combination
of genetic, psychological, and environmental factors is involved
in the onset of a depressive disorder. Later episodes of illness
typically are precipitated by only mild stresses or none at
all.
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