Physiology Behind Mood Disorders and Why You Are Anxious or Depressed

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Are you the type of person who weighs every decision, tries to determine every possible outcome and analyzes each risk before taking a single step? Are you moodier than those around you, more frequently negative, and more aware of pitfalls, both potential and real? If so, then a region of the brain just behind your right eye (if you are right-handed—left-handed people’s brains may differ) may be working overtime. Scientists have found that people who have a generally negative outlook on life show increased activity in an area of the brain called the ventromedial prefrontal cortex.

The ventromedial prefrontal cortex is the part of the brain that governs mood swings. While many areas of the brain are involved in producing emotions, this particular region acts as a sort of volume knob for those emotions, making them powerful or muted. This “volume” aspect of personality is what some people call temperament. Some temperaments are deemed “volatile,” for instance, while others are said to be “unflappable.”

David Zald, a psychologist at Vanderbilt University, led a study that sought to connect moods with brain activity in 89 people. Researchers purposely chose volunteers who had no history of medical or neurological problems, and none of whom were taking mood-altering medications. The researchers asked the volunteers to take detailed tests that measured their emotional outlook over the previous month. The questionnaires were designed to screen out people’s moods on the day of the test and their anxiety about test-taking, and to evaluate their general attitudes or temperament. After the volunteers filled out their questionnaires, researchers rated them on a scale of “negative affect.” Negative affect is a technical term for a range of unpleasant moods from irritability to anxiety to anger.

The researchers then performed brain scans on each subject, using positron emission tomography (PET) to record brain activity. In order to get an idea of a subject’s standard brain activity, the researchers looked at that subject’s brain while at rest. The researchers wanted to get an idea of how people’s brains operate all the time, not when they are directed toward a specific function, since brain activity changes during actions such as solving a puzzle, or remembering words. Zald’s team looked for areas of the brain that showed either increasing or decreasing activity during a resting state in people with more negative outlooks.

“The most striking positive correlation we found was localized in … the ventromedial prefrontal cortex,” Zald said. But he admits that even though there seems to be a connection between activity in this brain region and a negative outlook, that does not necessarily mean that brain activity is the only, or even main, cause. Personality is determined by more than simply physiology, though brain structure and function do contribute. “Because this is just a correlation, we don’t know whether this activity is the cause or the effect of negative mood states. Such a connection does make sense, however, because animal studies show that this region of the brain controls heart rate, breathing, stomach acidity levels, sweating and similar autonomous functions that have a close connection to mood.” Autonomous functions are those that operate without conscious effort.

The results revealed that people who reported generally high levels of anxiety, anger or depression had more active ventromedial prefrontal cortices (VMPFCs). But when people were given tasks to distract them, that region became less active. The decrease in activity correlated with a decrease in anxiety and negative affect while the task was being completed.

The researchers looked to see whether people with more positive outlooks also showed any corresponding activity in the VMPFCs, and found no correlation at all. The region is primarily associated with emotional intensity of negative affect, so it plays no role in positive emotions.

Research team member José Pardo told the Washington Post, “In a practical sense, what we know is a person with higher activity in this area can be predicted to have a high level of negative affect. High levels of negative affect have been shown to have a high risk of depression and anxiety. This may begin to tie aspects of temperament to disease.”

Hopefully, the discovery will one day lead to treatments for people with anxiety disorders or clinical depression.

On the other hand, people with negative affect cannot afford to simply “turn off” this region of the brain, or even temper its activity. Researchers find that people who have damage to this part of the brain (so that function is diminished) are not happier. Instead, they lack normal responses to emotional cues. This area of the brain is responsible for sensing danger, or even picking up on potential outcomes. People with brain damage in this area “don’t seem able to appreciate risk,” Zald told the Washington Post. “They can tell you they are doing something that has a good chance of failing, but they don’t have the emotional reaction to it—they don’t have visceral arousal. For example, if you are betting a lot of money, you may get a feeling in the pit of your stomach—they won’t experience that, they won’t get as upset about it.”

Some brain and body functions, though bothersome when taken to an extreme, are also extremely necessary. “Anxiety is often helpful to us—it is protective,” Zald said. “If you don’t have it, you are likely to not detect when you are in danger or when you are taking too big a risk.” Too much anxiety, though, becomes a barrier to living a normal life.

Sources

“Brain Activity in Ventromedial Prefrontal Cortex Correlates with Individual Differences in Negative Affect.” David Zald, Dorothy Mattson, José Pardo. Proceedings of the National Academy of Sciences. February 19, 2002, page 2450.

“Brain Part Appears to Accentuate Negativity.” Shankar Vedantam. Washington Post. February 12, 2002, page A8.

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