Prolonged Crying in Infants a Marker for Later Cognitive Problems
Infants who cry persistently in an uncontrollable manner without
any obvious cause after 12 weeks of age may be at risk for lower
IQ scores and poorer fine motor skills by the time they reach 5
years of age, according to researchers from the National Institute
of Child Health and Human Development of the National Institutes
The research appears in the November issue of Archives of Disease
"Prolonged infant crying is not only stressful for children's
families, it also can be a warning sign for a delay in children's
mental development," said Dr. Duane Alexander, Director of
the NICHD. "This study strongly suggests that we need to monitor
children who cried for prolonged periods as infants to ensure that
they're developing appropriately for their age level."
Researchers have studied colic, which is persistent crying that
occurs during the first few weeks of life up to three months of
age. However, there has been little research on prolonged crying,
which continues after an infant reaches three months of age, explained
the study's first author, Malla Rao, Ph.D., who conducted the study
while he was a researcher in NICHD's Division of Epidemiology, Statistics,
and Prevention Research.
To conduct the current study, Dr. Rao and his coworkers analyzed
information from an earlier study of pregnant women in Norway and
Sweden with one or two previous singleton births. After delivery,
the infants were evaluated during routine preventive care visits
at 6 and 13 weeks and again at 6, 9, and 13 months of age. The researchers
compared maternal and infant characteristics of normal infants,
infants with colic, and those with prolonged crying. The three groups
did not differ in the occurrence of birth complications or other
occurrences of the birth process, such as injury during birth or
admission to neonatal intensive care units. Of the 327 children
whose records were analyzed for the study, 48 were found to have
had colic and 15 were found to have had prolonged crying.
The researchers found that at 5 years of age, the 15 children who
had prolonged crying as infants had, on average, IQ scores 9 points
lower than those who had no crying problems. The prolonged crying
group also had significantly poorer eye-hand coordination. There
was no significant difference in IQ scores and eye-hand coordination
scores between children in the colic group and the normal infant
In addition, the researchers obtained information on personality
traits on a subset of nine children within the prolonged crying
group study who had taken a personality inventory test. Although
the researchers did not obtain enough information on a large enough
number of children to allow them to draw any firm conclusions, the
children's scores suggested that children who cry for prolonged
periods during infancy may also be more likely to later exhibit
behavioral problems such as hyperactivity or problems with discipline.
To explore the possibility that factors other than prolonged crying
might have been responsible for the children's developmental delays,
Dr. Rao and his colleagues compared the home environments and overall
health of children in the three groups. They found no differences.
The study also examined the effects of genetic factors, mothers'
IQ, and factors like the duration of exclusive breast feeding.
"This study supports earlier findings that colic does not
affect cognitive development," said Dr. Rao. "Prolonged
crying, on the other hand, appears to be related to cognitive problems.
It is not clear whether prolonged crying is a sign of delayed developmental
maturation since infants cry less as they mature, or whether irritability
caused by subtle underlying neurological problems is resulting in
The study also confirmed findings from earlier studies that mothers
who were smokers were twice as likely to have children with colic.
However, smoking was not associated with prolonged crying.
The NICHD is part of the National Institutes of Health (NIH),
the biomedical research arm of the federal government. NIH is an
agency of the U.S. Department of Health and Human Services. The
NICHD sponsors research on development, before and after birth;
maternal, child, and family health; reproductive biology and population
issues; and medical rehabilitation. NICHD publications, as well
as information about the Institute, are available from the NICHD
Web site, http://www.nichd.nih.gov,
or from the NICHD Information Resource Center, 1-800-370-2943; e-mail