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Causes of Eating Disorders - Biological Factors Continued

Bridget Engel, Psy.D., edited by Kathryn Patricelli, MA

While those with bulimia may have low levels of serotonin, other studies indicate that those with anorexia have high levels of neurotransmitters in some areas of the brain. For example, researchers in London found that those with anorexia have an overproduction of serotonin. This can cause a continual state of intense stress and anxiety. When a person with anorexia reduces intake of calories to starvation level, it leads to decreased levels of serotonin in the brain. This may result in a sense of calmness. The exact relationship between serotonin and anorexia has yet to be determined. Researchers are puzzled because medications that raise serotonin levels have been found to be a successful treatment for some with anorexia. This is confusing because those with anorexia already have high levels of serotonin. These scientists guess that that there may be different subtypes of anorexia with different neurochemicals involved.

neurons Researchers have also noted that abnormal eating behaviors and the resulting changes in the body can cause a disruption in serotonin levels. This contributes to an already existing problem. Abnormalities in serotonin levels can lead to depression and anxiety, both for under-eaters and over-eaters. It can also lead to other mental health conditions such as Obsessive Compulsive Disorder, Bipolar Disorder, Borderline Personality Disorder, and Attention Deficit/Hyperactivity Disorder (ADHD). Studies also suggest serotonin disruptions appear to run in some families.

New research suggests that women who develop anorexia may have altered levels of dopamine in their brains. Dopamine disturbances can cause hyperactivity, repetition of behavior (such as food restriction), and a decreased sense of pleasure. Dopamine also affects reward-motivated behavior. Improper levels of dopamine may explain why those with anorexia feel intensely driven to lose weight, yet feel little pleasure in shedding pounds.

Many other hormones in the brain have also been linked to eating disorders. Stress triggers the production and release of a hormone called cortisol. Ongoing high cortisol levels have been seen in patients with both anorexia and bulimia. Cortisol is very important in preparing multiple body systems to deal with threats. These systems include the heart, lungs, circulation, metabolism, immune systems, and skin. Increased cortisol also results in decreased appetite. This process may serve as a link between stressful conditions and the later development of eating disorders, although some imaging studies indicate that stress-hormone related changes occur after the disorders have developed. It is currently unclear whether changes in stress hormones are a cause or a result of eating disorders.

Leptin is a protein hormone produced by the body's fat tissue. This hormone travels to the brain, where it tells the body how much energy is available. This information plays a part in the regulation of reproduction, appetite, metabolism, and bone formation. If individuals with eating disorders lose extreme amounts of body fat, leptin levels drop. The side effects can include amenorrhea (when a female's period stops), impaired metabolism, and bone loss.

Leptin levels do not immediately return to normal when someone receives treatment for an eating disorder. Initially during therapy, levels often increase dramatically as people gain weight. Researchers think that during this period, individuals with eating disorders are at great risk for relapsing into disordered eating behavior and failing to maintain weight gains. For most people, it takes approximately 6 months or more of sustained, effective treatment before leptin levels return to normal. Because of this, it is crucial that people who are receiving therapy for eating disorders stick with a treatment program long-term (at least six months). This will ensure that their bodies are returning to normal hormone levels. As with stress hormones, it is not entirely clear whether changes in leptin levels are a cause or a result of eating disorders.