Serotonin Production Is Abnormal in Autistic Kids

By: Anna Nidecker, Staff Writer

[Clinical Psychiatry News 26(2):1, 1998. © 1998 International Medical
News Group.]

NEW ORLEANS -- Serotonin production appears to be disrupted during a
critical period of brain development in children and adolescents with
autism, Diane C. Chugani, Ph.D., said at the annual meeting of the
Society for Neuroscience.

Serotonin levels that are either too high or too low may disrupt the
production of new connections in the brain during childhood, a process
called synaptogenesis, said Dr. Chugani of the departments of
pediatrics, neurology, and radiology at Wayne State University, Detroit.

Using positron emission tomography, Dr. Chugani and her associates
measured the levels of a serotonin precursor in the brains of 15
children with autism, 6 of their siblings, and 10 children with

At all ages, autistic children showed altered levels of
alpha-methyl-tryptophan compared with their siblings and children with
epilepsy. Levels of alpha-methyl tryptophan, an analog of the serotonin
precursor tryptophan, are a reliable indicator of how much serotonin the
brain can synthesize, Dr. Chugani said.

Nonautistic children exhibited a rapid rise in the amount of serotonin
their brains could produce from age 3 months to 3 years, whereas
autistic children showed a gradual, low rise during this time period,
she reported.

In the nonautistic children, this capacity plateaued at three times
adult values between ages 3 and 8 years, when the process of
synaptogenesis occurs. After this stage, serotonin synthesis gradually
declined to adult values by 14 years of age.

In autistic children, however, the amount of serotonin increased
gradually between ages 2 and 12, showing no drop-off after age 8 and
plateauing at a value roughly twice that of nonautistic adults.

Both the low levels during childhood and abnormally high levels
approaching adolescence could disrupt the process of synaptogenesis, Dr.
Chugani said. She speculated that such developmental alterations caused
by abnormalities in serotonin synthesis capacity contribute to the
pathophysiology of autism.