Blood Markers Associated With Autism And Mental Retardation

The investigators examined and compared archived neonatal blood samples from children, born in four northern California counties from 1983 to 1985, who later developed autism, mental retardation, cerebral palsy, or developed normally. The investigators measured concentrations of several neural growth factors and found that the growth factors were significantly elevated in the neonatal blood of children who later developed autism or mental retardation, but not in the blood from children who developed cerebral palsy or blood from the normal controls.

“Finding that major regulators of brain development were different in children with autism from normal controls in the first days of life opens an exciting new avenue of research,” says Karin B. Nelson, M.D., Senior Investigator in the Neuroepidemiology Branch of the NINDS. “We think this work will be a step to better understanding the biologic basis of autism and hope it will lead to better ways to treat and perhaps prevent autism.”

“We have these promising new results because the California Department of Health Services had the foresight many years ago to save specimens from the newborn screening program,” added study co-author, Judith K. Grether, Ph.D., of the California Department of Health Services. “This archive of newborn blood specimens is an incredible treasure, providing a tremendously valuable resource for scientific study of a wide range of developmental disabilities and birth defects.”

Neural growth factors are important to the formation of the central nervous system during embryonic development. Previous research shows that many of these growth factors play a vital role in the production of new brain cells and the organization of those cells into distinct networks. The investigators hypothesize that an abnormal abundance of these proteins may disrupt the normal process of cell migration, differentiation, and programmed death during early nervous system development. Animal studies have shown that an early shortage of one of these proteins leads to microcephaly and other developmental problems.

The investigators speculate that a breakdown in the regulation of factors that influence early brain development is important in autism and mental retardation. Since these disorders cannot be clinically diagnosed until later in childhood, the identification of molecular markers could be helpful in the early diagnosis of the disorders and in the design of future clinical studies to test therapies. The researchers plan to continue their work to further elucidate the biological and genetic mechanisms that underlie the development of autism and other developmental disorders.

Autism is a pervasive developmental disorder that affects approximately 10 to 20 people in every 10,000 and affects males about four times more frequently than females. Symptoms of autism may surface in children around the age of 2. People with classical autism show three types of symptoms: impaired social interaction, problems with verbal and nonverbal communication, and unusual or severely limited activities and interests. People with autism may also show abnormal responses to sensory stimuli, such as touch, sounds, and sights. Twin studies suggest that autism has a strong genetic component.

Mental retardation is a term that is applied to people who show significantly delayed or impaired mental, intellectual, and social development. People with mental retardation generally score below 70 points on an intelligence quotient (IQ) test and have trouble adapting to complex social situations.

Cerebral palsy is a term used to describe a group of chronic disorders caused by faulty early development of or damage to motor areas in the brain. Symptoms of cerebral palsy include difficulties with control of limb movement. Some people with cerebral palsy may also have mental impairment.

(1) Nelson, K. B.; Grether, J. K.; Croen, L. A.; Dambrosia, J. M.; Dickens, B. F.; Jelliffe, L. L.; Hansen, R. L.; Phillips, T. M. “Neuropeptides and Neurotrophins in Neonatal Blood of Children with Autism or Mental Retardation.” Annals of Neurology, May 2001, Vol. 49(5), 597-606.

The NINDS, part of the National Institutes of Health in Bethesda, Maryland, is the nation’s leading supporter of research on the brain and nervous system. The NINDS is now celebrating its 50th anniversary.