Genetics and Depression
Scientists have already discovered that there is a genetic component to many diseases, such as cystic fibrosis, tuberous sclerosis, certain kinds of muscular dystrophy, Tay-Sachs, sickle cell anemia, and Huntington's disease.
Discovering that link is just the first step, however. Isolating that gene responsible for that disease and then finding a way to repair the gene takes time, an enormous amount of money, skill, persistence, and occasionally, luck. For many scientists and researchers, it's the work of a lifetime.
It's a Long Story
How do you study people? You can observe them, of course, but the data you collect might not be reliable. So, along with observation, researchers conduct physiological tests — blood tests, x-rays, CT scans, and other analytical tools at their disposal. Scientists also study the frequency of specific illnesses in certain families. For this kind of research, longitudinal studies are invaluable.
Longitudinal studies are investigations that follow specific individuals or groups over a period of years. In these studies, researchers are looking for trends and patterns. By gathering information from each generation, through medical records and oral histories, they are able to create a profile of how and when the disease manifests.
These studies have to be coupled with lab tests, since memories are notoriously unreliable. Still, longitudinal studies provide important information that scientists might otherwise be hard-pressed to discover.
If you know that a specific disease shows up in your family on a regular basis, be aware that depression may be a precursor or a symptom of that disease. Keep your medical records up to date, and always keep your annual physical exam part of your health regimen. Know the warning signs and be prepared to act on them.
Finding twins to participate in research studies is rather like striking gold at Sutter's Mill. Twin studies are rich sources of information for researchers, since identical twins share 100 percent of their genes and non-identical (fraternal) twins, 50 percent. Adoption studies are used to rule out the environmental factor.
Stanford University researchers found that depression occurred more often in identical twins than in non-identical twins. They discovered that the risk of developing depression was still greater for adopted twins, if their biological parent had depression. They also found that, if your parent or sibling suffers from major depression, you probably have a two to three times greater risk of developing depression yourself, than if they didn't. This figure may be higher for severe depression.
There are many different kinds of depression, and while scientists have recognized a genetic component for some, other psychological factors, along with physical and environmental factors, also play a role. Whether genetics is totally responsible for some forms of depression, or not responsible at all in others, remains to be determined.