By Silvia Helena Cardoso, PhD
Graphic Animation: André Malavazzi, graphic designer
People who suffer from anorexia/bulimia may
be born differences in brain chemistry that makes them prone to eating
disorders. It has been known for many years that
the brains of adult bulimics contain abnormal
levels of the classical neurotransmitter serotonin (5-HT) (Module 6; Principles
of Psychobiology), a neurotransmitter that
influences mood states, obsessive-compulsive
behaviors, and aggression.
It has
not been known whether these abnormal levels of 5-HT relate to the eating
disorder, or whether 5-HT levels are abnormal prior to the onset of the
eating disorder.
A recent study by Dr. Walter Kaye, professor
of psychiatry at the Western Psychiatric Institute in Pittsburgh, suggests
that serotonin levels may be abnormal before adult
bulimics begin the cycle of bingeing and
purging.
The study compared
31 healthy women with 30 women who once suffered from bulimia but had returned
to normal eating habits for at least a year. Serotonin levels
were measured in spinal fluid, and Kaye
found that recovered bulimics had abnormally high levels of serotonin.
Also, recovered bulimics showed many of the symptoms
associated with high levels of serotonin,
including negative moods and obsessions. Because all of the women in the
study had resumed healthy eating habits, the findings
indicate that diet, alone, cannot account
for the altered serotonin found in individuals who are exhibiting bulimia.
Instead, high serotonin levels may be a genetic condition that
leaves some people prone to the disorder,
Kaye said. Previous studies of twins of bulimics and anorexics also have
indicated that the eating disorders may be genetic, "so
there's accumulating evidence here."
Women
with high serotonin levels may be prone to eating disorders in part because
the elevated serotonin levels tend to make them depressed, anxious or obsessed
with
control, and starvation can lower the
level of serotonin. Serotonin is a product of tryptophan, which comes from
amino acids in food. "Their abnormal eating habits make
them feel temporarily better," Kaye said.
But the serotonin levels may then drop below normal, which can cause feelings
of impulsiveness, disorder and anxiety, so the bulimic person may binge
to bring the
serotonin back up again. "They start
to chase something they never really can catch," Kaye said.
