NEDA TOOLKIT for Parents
Neurotransmitters Although eating disorders result from the interplay of
a variety of cultural and biological factors, the brain
is central to understanding why some people develop
eating disorders, why people stay ill, and how they
can recover. In recent years, scientists have made
tremendous strides in understanding the brain science
of eating disorders.
Based on evidence from hundreds of studies, it
appears that one of the factors that make a person
more likely to develop an eating disorder is how their
brain functions. Researchers have identified specific
neurobiological differences in the brains of people
with anorexia, bulimia, or binge eating disorder. These
differences affect how we eat, as well as things like
mood, anxiety, personality, and decision-making.
This section will introduce you to the basics of eating
disorder neurobiology, and how various neural systems
work together in individuals with eating disorders.
Neurons Neurons send signals to each other using chemicals
known as neurotransmitters. The type and amount
of neurotransmitters released will tell neighboring
neurons whether to become active or to stay silent.
The body produces an array of neurotransmitters and
their receptors, which are proteins on the surface of the
cell that recognize a specific neurotransmitter and relay
the signal from the outside to the inside of the cell. Small
variations in the shape and number of receptors, as well
as the amount of neurotransmitter produced — known
as polymorphisms — exist in the population, which
increase or decrease the amount of neurotransmitter in
the synapse (the small space between a neuron and its
neighbors) and our sensitivity to it. These variations have
been linked to a variety of mental illnesses, including
eating disorders.
For eating disorders, there are two primary neurotrans-
mitters you need to know about: serotonin and dopa-
mine. Each of these neurotransmitters has an influence
in how we think and behave, our personalities, and even
perhaps our risk for developing an eating disorder.
Serotonin Given that serotonin (sometimes referred to as
5-hydroxytryptophan) helps control everything from
memory and learning to sleep, mood, and appetite,
researchers quickly began to look for potential
relationships between polymorphisms in serotonin
receptor genes and eating disorders.
A variety of studies have found alterations in the
serotonin system in individuals currently ill with
anorexia nervosa and those recovered from the
disorder. Researchers found that people who are
currently suffering from anorexia have significantly
lower levels of serotonin metabolites in their cerebro
spinal fluid than individuals without an eating disorder.
This is likely a sign of starvation, since the body
synthesizes serotonin from the food we eat. After
long-term recovery from anorexia, however, individuals
have significantly elevated serotonin levels (Kaye et al.,
1991). In this study, the researchers found that higher
levels of serotonin correspond with levels of anxiety
and obsessive behavior. Geneticists have also found
that individuals with anorexia are slightly more likely
to carry a particular variant of the 5HT2A serotonin
receptor, which is thought to increase the amount of
serotonin in the brain during the non-starved state
(Gorwood et al., 2002).
In an article published in 2009 in Nature Neuroscience,
leading eating disorder researcher Walter Kaye
hypothesizes that starvation actually makes people
with anorexia feel better by decreasing the serotonin
in their brains (Kaye, Fudge, & Paulus, 2009). As they
continue to starve themselves, however, the brain
responds by increasing the number of serotonin
receptors to more efficiently utilize the remaining
serotonin. So in order to keep feeling better, the
person needs to starve themselves further, creating the
illness’s vicious cycle. When someone with anorexia
starts eating again, however, serotonin levels spike,
causing extreme anxiety and emotional chaos, which
makes recovery difficult without adequate support.
Individuals with bulimia also have dysfunctions in
their serotonin circuitry. Those with bulimia, however,
appear to have somewhat different alterations than
those with anorexia. When going without food for
longer periods of time (such as during sleep), those
with bulimia had a larger drop in serotonin levels than
women without eating disorders, which led to binge
eating and increased irritability (Steiger et al., 2001).
Researchers also found that women with bulimia who
carried a particular variant of a serotonin receptor
were also significantly more impulsive (Bruce et al.,
2005). Abnormalities in the serotonin system were
also found to persist after recovery, hinting that these
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