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Biomedical Engineering

The Biomedical Engineering blog is the place for conversation and discussion about topics related to engineering principles of the medical field. Here, you'll find everything from discussions about emerging medical technologies to advances in medical research. The blog's owner, Chelsey H, is a graduate of Rensselaer Polytechnic Institute (RPI) with a degree in Biomedical Engineering.

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Treatments for Depression, Part 2

Posted January 20, 2016 12:00 AM by Chelsey H

Stress has been discussed many times on this blog. The dangers and benefits of stress are widely discussed in the scientific community as well as in the lifestyle industry concerning productivity and behavior. In part 1, we talked about early research on mental health issues and some current treatment options for those suffering with depression.

The stress hormone cortisol cycles daily to help when we need to pay attention to what's going on around us. Many studies find that in rodents and humans a mild increase in stress is good for the brain, particularly for memory. For example, students who get stressed while studying are more alert and remember more than those who feel no urgency - up to a point. Stress becomes a problem when there is too much at one moment such as in a rape or violent attack or too sustained as in long-term poverty, neglect, or abuse.

Stress changes the brain's architecture and the effect of hormones on the brain. For example, in a case of chronic stress, neurons in the hippocampus and the prefrontal cortex (mood and impulse control) start to shrink, while those in the amygdala (fear and anxiety) expand. However, everyone has different levels of vulnerability depending on genes and prior life experience. According to Maurizio Popoli, a professor of pharmacology at University of Milan, "it is because they perceive the stress differently." Image Credit

The role of the stress hormone is to flood parts of the brain with glutamate, the brain's "go" signal. Glutamate triggers neurons to generate sudden bursts of electricity that release more glutamate, which can trigger electrical bursts in nearby neurons. This function is called excitation and is fundamental to how information is processed in the brain. It ebbs and flows, meaning there is a "refractory period" following each neural firing during which the neuron cannot be excited.

Other neurotransmitters, like serotonin, are called "modulatory," because they change the sensitivity of neurons that secrete glutamate. As Popoli puts it, these modulators are "very important for fine-tuning the machine. But the machine itself is an excitatory machine," driven by glutamate.

Stress hormones affect the glutamate system along its journey through the brain. Stress causes more glutamate to be released, then block glial cells from removing the glutamate from the synapse, and block the glutamate from reaching its destination on the other side of the synapse. All of these changes increase the amount of glutamate in the synapse, flooding the cell with aberrant signals. A depressed person's brain, or at least animal models of depression, shows that all three of these problems lead to long-lasting excess glutamate in key portions of the brain. This makes a neuron fire sooner than it should and triggers a cascade of signals inside the cell damaging its structure. An overdose of glutamate causes the neurons and their dendrites (branches of the neuron) to shrink and after a time whole branches recede.

This dangerous process, called excitotoxicity, is thought to be involved in bipolar disorder, depression, epilepsy, and neurodegenerative diseases like Alzheimer's, Huntington's, and Parkinson's. In depressed brains, many area are shrunken and underactive.

Usually the brain's ability to adapt is considered a good thing; however in the case of mental disorders the human brain's flexibility allows regeneration, but also renders it vulnerable to being altered by stress. A traumatic event or a time of homelessness could cause a person with a genetic predisposition to find his mind stuck in a loop of chronic fear or depression.

In part 3 we'll discuss how drugs can be used to modify the effect of stress.


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Re: Treatments for Depression, Part 2

01/20/2016 1:46 PM

I realize there are multiple barriers (gastro-intestinal, blood-brain) in the human body that keeps foreign chemicals in our diet to not directly effect the brain. However, since your article specifically mentions glutamate as a neurotransmitter, might the consumption levels of MSG come into play here? Has this been studied?

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Re: Treatments for Depression, Part 2

01/20/2016 1:59 PM

I've been told that with seasonal depression is due to a lack of vitamin D and that by either taking vitamin D or going to a sun tanning booth will help.


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Re: Treatments for Depression, Part 2

01/21/2016 9:19 PM

I'm a believer that light therapy for mood elevation should not be pooh-poohed.

I couldn't understand why I felt so up in the dead of one winter but for the hours day after day I spent working at a bench illuminated by a 500W quartz light.


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Re: Treatments for Depression, Part 2

01/22/2016 2:28 PM

SAD lights have been used by coal miners to cope with Seasonal Affective Disorder that also affects people in Alaska. I remember an episode on Northern Exposure that Walt wore a light visor and became addicted to the visor.

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Re: Treatments for Depression, Part 2

01/29/2016 11:43 AM

I just searched for SAD and turned up a brand-new study questioning the validity of the SAD diagnosis. I wonder if the light is secondary to Vitamin D deficiency: less sunlight = less Vitamin D = perhaps more inclination to depression, along other issues Vitamin D deficiency brings about.

Despite this new study, there is a lot of anecdotal evidence that use of full-spectrum lights have at least a placebo effect. Don't know of these lights have anything to do with Vitamin D. A friend of mine who quilts and does other handcrafts noticed a correlation between using a full-spectrum lamp when crafting during the winter and improved mood. But it could be that just doing an activity she likes, and that takes concentration, were just as important mood-changers. So difficult to control for all the variables. And one has to take into consideration who sponsored the research.


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Re: Treatments for Depression, Part 2

07/24/2019 3:34 AM

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