Learning Disabilities and Intellectual Functioning in School-Aged Children with Prenatal Cocaine Exposure

Connie E. Morrow, Jan L. Culbertson, Veronica H. Accornero, Lihua Xue, James C. Anthony, Emmalee S. Bandstra

First Published: 12  February 2009 DIO: 10.1207/s15326942dn3003_8

Department of Pediatrics, University of Miami School of Medicine, Miami, FL 33101, USA.

Abstract

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Risk for developing a learning disability (LD) or impaired intellectual functioning by age 7 was assessed in full-term children with prenatal cocaine exposure drawn from a cohort of 476 children born full term and enrolled prospectively at birth. Intellectual functioning was assessed using the Wechsler Intelligence Scale for Children-Third Edition short form, and academic functioning was assessed using the Wechsler Individual Achievement Test Screener by examiners blind to exposure status. LDs were categorized based on ability-achievement discrepancy scores, using the regression-based predicted achievement method described in the WIAT manual. The sample in this report included 409 children (212 cocaine-exposed, 197 non-cocaine-exposed) from the birth cohort with available data. Cumulative incidence proportions and relative risk values were estimated using STATA software. No differences were found in the estimate of relative risk for impaired intellectual functioning (IQ below 70) between children with and without prenatal cocaine exposure (estimated relative risk = .95; 95% confidence interval [CI] = 0.65, 1.39; p = .79). The cocaine-exposed children had 2.8 times greater risk of developing an LD by age 7 than non-cocaine-exposed children (95% CI = 1.05, 7.67; p = .038; IQ >/= 70 cutoffs). Results remained stable with adjustment for multiple child and caregiver covariates, suggesting that children with prenatal cocaine exposure are at increased risk for developing a learning disability by age 7 when compared to their non-cocaine-exposed peers.

Academic casualty, including the continuum of learning disorders and lower intellectual functioning requiring educational assistance, has enormous impact on the individual child and family as well as the systems that must support and care for children with disabilities. Recent data from the U.S. Department of Education revealed that over 5.7 million students ages 6 through 21 years received services under the Individuals with Disabilities Education Act, Part B, during the 2000–2001 school year. This figure represents 11.5% of the estimated student enrollment in public schools for grades kindergarten through twelfth grade. Of children receiving special services, 2,887,217 (50%) were identified as having specific learning disabilities (LD) and 612,978 (10.6%) were identified as having mental retardation.

According to the Special Education Expenditure Project, per-pupil special education expenditures for students with LD average $10,558, compared with per-pupil expenditures of $6,556 for students who do not receive special education services. Thus, educational costs for students with LD is 1.6 times the amount expended for students without special needs.  For students with mental retardation and LD, their diminished academic functioning and the impact on opportunities for employment and economic productivity have lifelong consequences. Thus, examination of populations who may have increased risk for these types of disabilities is important at the level of the affected individual as well as the educational and public health system levels.

Over the past decade significant concern has been raised regarding the public health impact of maternal cocaine use during pregnancy and the potential for long-term clinically devastating outcomes for infant and child development. The teratological approach examines whether there is an increased risk of neurodevelopmental impairments including physical malformation, growth abnormalities, or abnormal developmental functions as a result of exposure to a toxic agent. Cocaine, a potential teratogen, readily crosses the placenta and is believed to impact the developing monoaminergic neurotransmitter systems, disrupting both structural and functional aspects of fetal brain development. Monoaminergic neurotransmitters appear early in fetal brain development and are important in the development of neuronal circuitry, with the norepinephrine and serotonin systems extending throughout the brain. Accordingly, cocaine’s influence on these systems may yield more generalized deficits, whereas the impact on monoaminergic pathways involving dopamine is likely to be more focused. 

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