WEB MD myth busters include this observation: "Depression affects nearly one in six people at some point in their lives, so folk remedies and half-truths about this common illness abound. One such idea: throw yourself into work and you'll feel better. For a mild case of the blues, this may indeed help, but depression is a different animal. Overworking can actually be a sign of clinical depression, especially in men." On Sounds Good, we continue a conversation about understanding depression with Murray State University assistant professor of psychology, Dr. Michael Bordieri, with an exploration of the biology of depression, including the serotonin hypothesis.
What is the biology of depression?
Dr. Bordieri says researchers have spent the last 30 to 50 years trying to answer this question. The short answer is: no consensus. The long answer is: theories range from chemicals in the brain to genetics to blood testing, but there is no unified answer.
There is no doubt that there are implications on the biological level - the limbic system in the brain consists of structures involved in emotion, emotional memories, fear processing, etc. A wealth of studies exist suggesting structural changes or other sorts of implications occurring in that system are because of depression, but the actual mechanism, or trigger, is unclear. Some studies suggest a genetic link, but nothing is clear yet. Bordieri says that depression appears to be a polygenic condition, where multiple factors come together.
Depression research is a tough area to talk about, he says, because people want an explanation they can understand. Unfortunately, the best evidence suggests that we are simply not there yet as a science.
Markers for Depression?
Markers in a brain scan can vary. So far, there aren't any specific markers for depression, however there are other biological factors that can show markers that may lead to or be a result of depression. A new study looking at blood testing suggests different detectable molecules in the blood that might differentiate between depressed and non-depressed patients. It's still in preliminary findings, but if it proves to be a reliable test, it could change the landscape of understanding the biology of depression.
Serotonin Hypothesis
There are two focus areas of the brain when considering depression: the hippocampus, involved in memory and some emotional processing; and the amygdala, the heart of what we consider emotional processing.
The prevailing theory of medicinal treatment today involves serotonin, which has been marketed for the past 30 years as the prevailing cause of depression. Antidepressant drugs like Prozac are selective serotonin reuptake inhibitors (SSRIs). These drugs work by inhibiting the reuptake of serotonin, which increases the amount of serotonin in the brain. So the prevailing theory for a long while in scientific theory and in popular culture is that depression is caused by a chemical imbalance and that certain drugs can fix the imbalance. Dr. Bordieri uses the analogy of a car running low on oil not running smoothly. Add more oil and the car is fine. It's a nice, simple story to understand, he says, but new data doesn't support this theory. The serotonin hypothesis no longer has widespread scientific support.
Recently, researchers have bred a type of mice that didn't have a gene of serotonin. When put through a series of tasks: swim test, suspending from tail to see how long until they gave up - they found that these mice behaved like typical mice, not mice showing typical signs of depression. This find puts into question whether serotonin levels effect depression.
Just because some antidepressants show some evidence of working doesn't necessarily mean that the lack of serotonin, which is what the medication is treating, is the cause of depression. Also, there is a high relapse rate when the drug is removed, which raises the question of what's really going on in the body? Medication for depression as the primary treatment has societal implications we're still trying to understand as a community. 20-40 years ago, depressive episodes were common, but usually as singular events. Now, we're seeing depression as a chronic illness, and in trying to resolve why this is, also trying to find biological answers.
The next discussion airs Tuesday, December 2 and will be a continuation on the topic of the biology of depression.
This is the sixth in a series of conversations about depression with Dr. Michael Bordieri, assistant professor of psychology at Murray State. Dr. Bordieri's contributions to this series are strictly informational and should not be construed as any form of psychotherapy, counseling, diagnosis or treatment. Any health condition, including depression, should be evaluated and treated by a qualified professional in the context of an established professional relationship.
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