Scientists are beginning to understand the connection between brain atrophy, neurogenesis, and depression. What happens within the brain when a person is depressed? Our concept of that is rapidly shifting, thanks to work in brain imaging and molecular medicine. In the late 1990s, several lines of research began turning our concept of mood disorders upside down.
NEW BRAIN CELL GROWTH CONTINUES THROUGHOUT LIFE
Taken chronologically, the first step was research showing that neurogenesis — the birth of new brain cells — can continue throughout life. Most of us remember being told that we’re born with all the brain cells we’ll ever have. Not true. We now know that the process of neurogenesis is an ongoing one, with new brain cells being born even as old brain cells die off.
DAMAGE TO BRAIN CAUSED BY DEPRESSION
The second was evidence that depression is associated with loss of volume in parts of the brain. Researchers have also found that depression appears to inhibit this birth of new brain cells. And that may help explain the second line of research — why people who’ve had depression are likelier to have a smaller hippocampus (a part of the brain that plays a role in emotion and is associated with memory and learning). The more severe and long-lasting the depression, the greater the loss of brain volume.
This process of brain atrophy also affects the frontal lobes, which are involved in managing emotional reactions. The good news is that most of the change seems to be related to cell shrinkage, rather than outright cell death, and thus can potentially be reversed. Genetic studies have also found a subgroup of people more susceptible to this process of brain atrophy.
WHAT ABOUT NEUROTRANSMITTERS?
Where does this leave familiar neurotransmitters such as serotonin and norepinephrine? They are still understood to play a significant role in mood disorders — but with a new twist. Most people are familiar with the research that underlies the use of fluoxetine (Prozac) and similar antidepressants. These drugs block the reuptake of certain neurotransmitters at receptor sites in the brain, thus increasing the concentrations of serotonin and other neurotransmitters in the synapses (gaps) between cells in the brain. This increase is believed to be responsible for the elevation of mood.
ACTIONS WITHIN THE CELLS
The twist? More recently, instead of focusing on tinkering with the level of neurotransmitters between cells, researchers have looked at what happens when the neurotransmitter binds to the cell membrane. The reactions that then go on inside the cell are now thought to be more important to the cell’s functioning than the binding of the neurotransmitter to the outside. For instance, researchers have found that antidepressants increase levels of brain-derived neurotrophic factor (BDNF), which helps nourish neurons, aiding them in becoming more active and make more connections to other cells. Researchers also have found that antidepressants are involved in neurogenesis — at least in rats — increasing the production of new neurons in the rat hippocampus.
THE ROLE OF EXERCISE VERSUS STRESS
In animal studies, stress puts a halt to the process of neurogenesis. Under stress, existing cells shrink and the total number of cells decreases. Exercise and “environmental enrichment,” on the other hand, have a beneficial effect.
In humans, there are hints that exercise may help reverse brain atrophy. Treatment with antidepressants also has been found to be effective, although the extent of the response varies among individuals and may be moderated by how severe a person’s depression has been, and how often it has recurred. And psychotherapy still has a role to play because how we interpret a stressful event can have a significant impact on our emotional response and ability to recover.
HOW MUCH EXERCISE?
According to John Ratey, MD, author of Spark: The Revolutionary New
Science of Exercise and the Brain www.amazon.com a simple equation can help you get on target for the right amount of activity. “An exercise regimen can work as well as an antidepressant,” says Dr. Ratey. The equation is to multiply your body weight by 8 to find the number of calories you need to burn each week. Once you come up with that total, go online to a calorie-burning site, such as www.calorieking.com or www.my-calorie-counter.com to find the amount of time per activity you will need to expend to reach your goal. As an example, the list below shows a few activities and the number of minutes it takes for a 135-pound woman to burn 200 calories:
Walking (4 mph, brisk) — 37 minutes
Aerobics — 29 minutes
Dance (general) — 29 minutes
Elliptical Trainer — 29 minutes
Spinning (moderate) — 27 minutes
Jogging (5 mph) — 24 minutes
Swimming — 19 minutes
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Disclaimer: The purpose of this weblog is not to dispense medical advice nor in any way is meant to be construed as diagnostic or prescriptive. Always check with your physician before beginning any new program or trying any of the items discussed in the posts that appear on this site.





















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