Are there neurologic correlates of in utero cocaine exposure at age 6 years?

Effect of socioeconomic status disparity on child language and neural outcome: how early is early?

It is not news that poverty adversely affects child outcome. The literature is replete with reports of deleterious effects on developmental outcome, cognitive function, and school performance in children and youth. Causative factors include poor nutrition, exposure to toxins, inadequate parenting, lack of cognitive stimulation, unstable social support, genetics, and toxic environments. Less is known regarding how early in life adverse effects may be detected. This review proposes to elucidate "how early is early" through discussion of seminal articles related to the effect of socioeconomic status on language outcome and a discussion of the emerging literature on effects of socioeconomic status disparity on brain structure in very young children. Given the young ages at which such outcomes are detected, the critical need for early targeted interventions for our youngest is underscored. Further, the fiscal reasonableness of initiating quality interventions supports these initiatives. As early life adversity produces lasting and deleterious effects on developmental outcome and brain structure, increased focus on programs and policies directed to reducing the impact of socioeconomic disparities is essential.

Longitudinal follow-up of poor inner-city youth between ages 8 and 18: intentions versus reality

OBJECTIVES

(1) To document, at ages 8 to 10, children's perceptions of their future and, at ages 16 to 18, youth outcomes; and (2) to assess early childhood factors associated with trajectory-altering events (TAEs), defined as youth risk behaviors that may modify developmental trajectories.

METHODS

A prospective longitudinal study of 97 poor, inner-city, African American youth followed since birth who completed (1) early childhood environment, cognitive, and social-emotional evaluations, as well as an inventory at ages 8 to 10 of perceptions of their futures; and (2) evaluation for presence or absence of 4 TAEs documented at ages 16 to 18: drug use, adjudication, school failure, and teen parenthood.

RESULTS

At age 9.4 ± 0.5, 94% of participants felt it unlikely they would try marijuana; 93% felt they were unlikely to get arrested; 92% felt they were likely to attend college or trade school; 81% did not know one could become pregnant with first-time sex. Age 18.1 ± 0.8 outcomes showed that 33% had used drugs, 33% had been adjudicated, 19% had school failure, and 20% had become parents. Fifty-six percent had ≥1 TAE. No relationship was found between childhood perceptions and intentions and documented outcomes. Odds of having a TAE increased with greater exposure to violence and poorer home environment.

CONCLUSIONS

Young inner-city children are idealistic regarding their future. By ages 16 to 18 however, more than half of this cohort had a TAE. Factors most strongly associated with a TAE were greater exposure to violence and poorer home environment.

Prenatal cocaine exposure: Effects on mother- and teacher-rated behavior problems and growth in school-age children

In this longitudinal study of prenatal cocaine exposure (PCE), school-age physical and cognitive development and behavioral characteristics were examined, while controlling for other factors that affect child development. At this follow-up phase, children were on average 7.2 years old, and their caregivers were 33.7 years old, had 12.5 years of education, and 48% were African American. During the first trimester, 20% of the women were frequent cocaine users (≥1 line/day). First trimester cocaine exposure predicted decreased weight and height at 7 years. There was no significant relationship between PCE and the cognitive and neuropsychological measures. Third trimester cocaine use predicted more total and externalizing behavior problems on the Child Behavior Checklist (Achenbach, 1991 [3]) and the Teacher Report Form (Achenbach, 1991 [4]), and increased activity, inattention, and impulsivity on the Routh Activity (Routh et al., 1974 [67]) and SNAP scales (Pelham and Bender, 1982 [55]). Children who were exposed to cocaine throughout pregnancy had more mother- and teacher-rated behavior problems compared to children of women who stopped using early in pregnancy or who never used cocaine prenatally. These detrimental effects of PCE on behavior are consistent with other reports in the literature and with the hypothesis that PCE affects development through changes in neurotransmitter systems. These school-age behaviors may be precursors of later adolescent behavior problems.

Early parental care is important for hippocampal maturation: evidence from brain morphology in humans

The effects of early life experience on later brain structure and function have been studied extensively in animals, yet the relationship between childhood experience and normal brain development in humans remains largely unknown. Using a unique longitudinal data set including ecologically valid in-home measures of early experience during childhood (at age 4 and 8 years) and high-resolution structural brain imaging during adolescence (mean age 14 years), we examined the effects on later brain morphology of two dimensions of early experience: parental nurturance and environmental stimulation. Parental nurturance at age 4 predicts the volume of the left hippocampus in adolescence, with better nurturance associated with smaller hippocampal volume. In contrast, environmental stimulation did not correlate with hippocampal volume. Moreover, the association between hippocampal volume and parental nurturance disappears at age 8, supporting the existence of a sensitive developmental period for brain maturation. These findings indicate that variation in normal childhood experience is associated with differences in brain morphology, and hippocampal volume is specifically associated with early parental nurturance. Our results provide neuroimaging evidence supporting the important role of warm parental care during early childhood for brain maturation.

Executive functioning at ages 5 and 7 years in children with prenatal cocaine exposure

This prospective longitudinal study evaluated the effect of prenatal cocaine exposure (PCE) on executive functioning in 5- and 7-year-old children. In total, 154 pregnant cocaine users, identified by urine toxicology and structured interviews, were matched to 154 nonusers. Children were assessed by certified masked evaluators, and caregivers were interviewed by experienced staff during home visits. In approximately 90% of the surviving sample tested at ages 5 and 7 years, structural equation modeling demonstrated that an increased head circumference at birth (adjusted for gestation) significantly predicted better performance on executive functioning, and that PCE was indirectly related to executive functioning through its significant negative effect on head circumference at birth. At age 5 years, quality of environment also predicted executive functioning, and the R(2) for the total model was 0.24. At 7 years, caregiver functioning predicted quality of environment, which in turn was positively related to executive functioning, and girls had better executive functioning. The total model at age 7 years accounted for 30% of the variance in executive functioning.

Prenatal drug exposure: effects on cognitive functioning at 5 years of age

The goal of this cross-sectional study was to compare cognitive functioning at age 5 years in prenatal drug-exposed children with nondrug-exposed children from a comparable inner-city environment. Children with prenatal drug exposure scored significantly lower on measures of language, school readiness skills, impulse control, and visual attention span/sequencing than controls matched for age and socioeconomic status. Intelligence, visual-motor, manual dexterity, and sustained attention scores were not significantly different between groups. The total sample scored significantly below the normative mean on standardized measures of intelligence, language, school readiness, visual-motor skills, impulse control, and sustained attention, with 40% scoring at least 1 standard deviation below the mean (IQ < 85) on a measure of intelligence. Findings suggest that children with prenatal drug exposure are at increased risk for learning and attention problems and are in need of close developmental surveillance and possible intervention to support school success and improve behavioral outcome.

Altered resting cerebral blood flow in adolescents with in utero cocaine exposure revealed by perfusion functional MRI

OBJECTIVES

Animal studies have clearly demonstrated the effects of in utero cocaine exposure on neural ontogeny, especially in dopamine-rich areas of cerebral cortex; however, less is known about how in utero cocaine exposure affects longitudinal neurocognitive development of the human brain. We used continuous arterial spin-labeling perfusion functional MRI to measure the effect of in utero cocaine exposure on resting brain function by comparing resting cerebral blood flow of cocaine-exposed adolescents with non-cocaine-exposed control subjects.

PATIENTS AND METHODS

Twenty-four cocaine-exposed adolescents and 25 matched non-cocaine-exposed control subjects underwent structural and perfusion functional MRI during resting states. Direct subtraction, voxel-wise general linear modeling, and region-of-interest analyses were performed on the cerebral blood flow images to compare the resting cerebral blood flow between the 2 groups.

RESULTS

Compared with control subjects, cocaine-exposed adolescents showed significantly reduced global cerebral blood flow. The decrease of cerebral blood flow in cocaine-exposed adolescents was observed mainly in posterior and inferior brain regions, including the occipital cortex and thalamus. After adjusting for global cerebral blood flow, however, a significant increase in relative cerebral blood flow in cocaine-exposed adolescents was found in anterior and superior brain regions, including the prefrontal, cingulate, insular, amygdala, and superior parietal cortex. Furthermore, the functional modulations by in utero cocaine exposure on all of these regions except amygdala cannot be accounted for by the variation in brain anatomy.

CONCLUSIONS

In utero cocaine exposure may reduce global cerebral blood flow, and this reduction may persist into adolescence. The relative increase of cerebral blood flow in anterior and superior brain regions in cocaine-exposed adolescent participants suggests that compensatory mechanisms for reduced global cerebral blood flow may develop during neural ontogeny. Arterial spin-labeling perfusion MRI may be a valuable tool for investigating the long-term effects of in utero drug exposure.

Learning disabilities and intellectual functioning in school-aged children with prenatal cocaine exposure

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 (Wechsler, 1991) short form, and academic functioning was assessed using the Wechsler Individual Achievement Test (WIAT; Wechsler, 1993) 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 (Statacorp, 2003). 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 a LD by age 7 than non-cocaine-exposed children (95% CI = 1.05, 7.67; p = .038; IQ >/= 70 cutoff). 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.

Impact of prenatal cocaine exposure on child behavior problems through school age

OBJECTIVE

We examined the trajectory of childhood behavior problems after prenatal cocaine exposure.

METHODS

The Maternal Lifestyle Study, a longitudinal cohort study, enrolled children between 1993 and 1995 at 4 centers. Prenatal cocaine exposure was determined from mothers who admitted use and/or meconium results. Exposed children were matched with a group of nonexposed children within site and by gestational age, gender, race, and ethnicity. The study began at the 1-month corrected age with a total of 1388 children enrolled. A total of 1056 were assessed for internalizing, externalizing, and total behavior problems at ages 3, 5, and 7 years using the Child Behavior Checklist. Longitudinal hierarchical linear models were used to determine the effect of prenatal cocaine exposure on behavior problem trajectories while controlling for other prenatal exposures; time-varying covariates, including ongoing caregiver use of legal and illegal substances; demographic factors; family violence; and caregiver psychological distress.

RESULTS

High prenatal cocaine exposure was associated with the trajectory of internalizing, externalizing, and total behavior problems; these effects were independent of and less than the significant combined effect of prenatal and postnatal tobacco and alcohol exposures. Caregiver depression and family violence had independent negative influence on all behavior outcomes.

CONCLUSIONS

Prenatal cocaine exposure has a negative impact on the trajectories of childhood behavior outcomes. When they co-occur with prenatal cocaine exposure, prenatal and postnatal tobacco and alcohol exposures have added negative effects on behavior outcomes.