Who Has Clinical Depression
Q: Much of what we know about the genetic influence of clinical depression is
based upon research that has been done with identical twins. Identical twins
are very helpful to researchers since they both have the exact same genetic
code. It has been found that when one identical twin becomes depressed the
other will also develop clinical depression approximately 76% of the time.
When identical twins are raised apart from each other, they will both become
depressed about 67% of the time. Because both twins become depressed at such
a high rate, the implication is that there is a strong genetic influence. If
it happened that when one twin becomes clinically depressed the other always
develops depression, then clinical depression would likely be entirely
genetic. However because the rate of both identical twins developing
depression is not closer to 100% this tells us that there are other things
that influence a person's vulnerability to depression. These may include
environmental factors such as childhood experiences, current stressors,
traumatic events, exposure to substances, medical illnesses, etc.
A:Research has also been done with fraternal twins. Unlike identical twins who
have the same genetic code, these siblings share only about 50% of their
genetic makeup and do not necessarily look alike. Studies have shown that
when one fraternal twin becomes depressed, the other also develops depression
about 19% of the time. This is still a higher rate of depression when compared to
overall rates for the general public, again pointing towards a genetic
influence in the development of clinical depression.
Bipolar Disorder
It has long been known that depressive illnesses can run in families, but
until fairly recently it was not fully known whether people inherited a
susceptibility to these illnesses or if something else such as the
environment
was the true culprit. Those who research depression have been able to
determine that to some extent depressive illnesses can be inherited. What
appears to be inherited is a vulnerability to depression. This means that if
we have close relatives who have clinical depression, we may inherit a
tendency to develop the illness. It does not mean that we are destined to
become depressed.
Genes that we inherit from our parents determine many things about us such
as our gender and the color of our eyes and hair. Our genes also determine
which illnesses we may be vulnerable to at some point in our lives. Every cell in
the human body contains somewhere between 50,000 and 100,000 genes. They are
all made up of something called deoxyribonucleic acid, or DN
A: Genes are located on chromosomes within the nucleus of each cell. All of the cells in the body, except sex cells, contain 46 chromosomes, and genes are typically located in a specific place on a particular chromosome. Except for identical twins, no two people in the world have the exact same genetic makeup. Research on the heredity of depression within families shows that some individuals are more likely to develop the illness than others. If you have a parent or sibling that has had major depression, you may be 1.5 to 3 times more likely to develop the condition than those who do not have a close relative with the condition. You would also have a higher chance of developing bipolar disorder. Because close relatives of those with clinical depression have such a vulnerability to developing the condition themselves strongly suggests that it can be an inherited illness. Bipolar disorder has a strong genetic influence. Of those with bipolar disorder, approximately 50% of them have a parent with a history of clinical depression. When a mother or father has bipolar disorder, their child will have a 25% chance of developing some type of clinical depression. If both parents have bipolar disorder, the chance of their child also developing bipolar disorder is between 50% and 75%. Brothers and sisters of those with bipolar disorder may be 8 to 18 times more likely to develop bipolar disorder, and 2 to 10 times