What about Genetic or Biological Factors?
There is now little doubt that genetic factors play a role in depression. The scientific evidence on genetics comes from two major findings. First, depression tends to run in families. When an illness is common among family members, it is often assumed to have at least some genetic component, although families share much more than their genes. Second, identical twins raised in separate family environments tend to have related symptoms of depression more often than nonidentical twins who are raised in the same family environment do (Gatz et al. 1992). Because identical twins in these studies share all the same genetic material but not the same family environment, these findings suggest that genetic factors playa role in depression.
Notice the words “playa role.” We didn’t say “cause” or “are the reason for,” because no research has shown that depression is caused specifically by-and only by-genetics. As mentioned before, there is an equally strong body of research pointing to the importance of life events in leading to depression. In addition, many people are able to end depression by changing their behavior, the way they think, or other nongenetic or biological processes. Thus, the approach described here can be helpful regardless of whether depression is ultimately found to have a genetic basis.
