Twin Studies Link Depression to Genetic/Biological Causes ?

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.

A.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. 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 more likely to develop major depressive disorder than others with no such siblings. I think that this sort of study in indubitably convincing. And if there is any question, about the veracity of inherited mental illness it would have to be in the description of it alone. It would be hard to see what gene or combination of genes or genes acting with embryonic chemical conditions could result in bipolar illness, but that twins have such a high percentage probability of getting it, leaves the matter clear as an unmuddied lake to me. The treatment is another matter. For it is one thing to treat the illness and quite another to treat it with minimum side effects.

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