Marty is correct.
WebMD has useful information about the multiple causes as well.
How Is Biology Related to Depression?
Researchers have noted differences in the brains of people who are depressed as compared to people who are not. For instance, the hippocampus, a small part of the brain that is vital to the storage of memories, appears to be smaller in people with a history of depression than in those who've never been depressed. A smaller hippocampus has fewer serotonin receptors. Serotonin is a calming brain chemical known as a neurotransmitter that allows communication between nerves in the brain and the body. It's also thought that the neurotransmitter norepinephrine may be involved in depression.
Scientists do not know why the hippocampus is smaller in those with depression. Some researchers have found that the stress hormone cortisol is produced in excess in depressed people. These investigators believe that cortisol has a toxic or poisonous effect on the hippocampus. Some experts theorize that depressed people are simply born with a smaller hippocampus and are therefore inclined to suffer from depression.
One thing is certain -- depression is a complex illness with many contributing factors. The latest scans and studies of brain chemistry that show the effects of antidepressants help broaden our understanding of the biochemical processes involved in depression. As scientists gain a better understanding of the cause(s) of depression, health professionals will be able to make better "tailored" diagnoses and, in turn, prescribe more effective treatment plans.
How Is Genetics Linked to the Risk of Depression?
We know that depression seems to run in families. This suggests that there's a genetic link to depression. Children, siblings, and parents of people with severe depression are much more likely to suffer from depression than are members of the general population. Multiple genes interacting with one another in special ways probably contribute to the various types of depression that run in families. Yet despite all the evidence of a family link to depression, scientists still have not been able to identify a "depression" gene.
- 4/19/2011 9:44:02 AM