Parents of children with autism are often frustrated by not knowing the actual cause or causes of the disorder. Studies have hinted at a variety of factors that may heighten a child’s risk, but a new research review says there is still too little evidence to point to a direct link.
Researchers did discover, while reviewing 40 previous studies, that there appears to be a range of factors at birth that have been tied to the risk of autism later in life. Their findings determined that certain delivery complications such as problems with the umbilical cord, fetal distress during labor and signs of “poor condition” in the newborn – like problems with breathing or heart rate- may be contributors to autism.
But even results from these studies often drew conflicting conclusions as to whether any one of the factors mentioned were actually related to future autism.
In a complex disorder like autism, it would be very unlikely that a single birth factor would stand out as the key culprit, explained Hannah Gardener, a researcher at the University of Miami School of Medicine who led the study.
Gardener stresses that the parents of children who may have one these problems at birth should not be alarmed.
“It’s important that parents not worry about any particular one of these risk factors.”
Moreover, autism is generally believed to involve a complex interaction between genes and environmental factors.
The current findings, Gardener said, underscore the importance of continuing to study which environmental factors — whether before, during or after birth — may act in concert with genetics to cause autism.
“There is no single strong cause of autism,” said Gardener, who was at the Harvard School of Public Health at the time of the study.
Autism is a general term used to describe a group of complex developmental brain disorders known as Pervasive Developmental Disorders (PDD). Other disorders are Asperger Syndrome, Rett Syndrome and Childhood Disintegrative Disorder. Many parents and professionals refer to this group as Autism Spectrum Disorders.
Although there is no known cause of autism, many experts believe that there is a genetic connection.
Rueters reports Gardener says that one problem in the studies is that they have focused on a relatively small groups of children. So for their study, her team combined the results of 40 studies — in what’s called a meta-analysis.
They found that a number of “perinatal” (around the time of birth) and newborn factors were linked to autism — that is, infants affected by those factors were relatively more likely to go on to develop autism than unaffected infants.
Along with low birth weight, fetal distress, and umbilical cord-problems (the cord being wrapped around the baby’s neck, for instance), other factors included multiple birth, birth injuries to the baby, maternal hemorrhaging during childbirth, anemia or jaundice in the newborn. Another was low Apgar score — a measure of a newborn’s general health that includes heart rate, breathing and muscle tone.
But, the researchers write, there was “insufficient evidence to implicate any one perinatal or neonatal factor in autism etiology.”
All the perinatal factors mentioned in the review don’t necessarily point to one cause, but evidence shows that combining more than one factor seems to increase the possibility of a child developing autism – perhaps because of the compromised health of the newborn.
The current study also found that factors such as the use of anesthesia, forceps or vacuum during childbirth, high birth weight and newborn head circumference did not show a relationship to autism.
Gardener and her colleagues have reported their findings in the journal Pediatrics.
Autism affects 1 in 110 children with 1 in 70 affecting boys. It varies widely in severity and symptoms and may go unrecognized, especially in mildly affected children or when more debilitating handicaps mask it.
• No babbling or pointing by age 1
• No single words by 16 months or two-word phrases by age 2
• No response to name
• Loss of language or social skills
• Poor eye contact
• Excessive lining up of toys or objects
• No smiling or social responsiveness.
Later indicators include:
• Impaired ability to make friends with peers
• Impaired ability to initiate or sustain a conversation with others
• Absence or impairment of imaginative and social play
• Stereotyped, repetitive, or unusual use of language
• Restricted patterns of interest that are abnormal in intensity or focus
• Preoccupation with certain objects or subjects
• Inflexible adherence to specific routines or rituals.
Experts continue to study autism hoping to find the gene or cause that will help them discover a cure or treatment. Parents meanwhile, continue to take care of and love their autistic child and hope to someday have qualitative answers to their many questions.