school performance of children with gestational cocaine exposure

www.elsevier.com/locate/neutera

Neurotoxicology and Teratol

School performance of children with gestational cocaine exposure

Hallam Hurta,*, Nancy L. Brodskya, Hallam Rothb, Elsa Malmuda, Joan M. Giannettaa

aNeonatology, Department of Pediatrics, University of Pennsylvania School of Medicine, The Children’s Hospital of Philadelphia,

Philadelphia, PA, United StatesbUniversity of Virginia, Charlottesville, VA, United States

Received 23 January 2004; received in revised form 23 September 2004; accepted 21 October 2004

Available online 26 November 2004

Abstract

Objective: To document school performance (pass/fail, grade point average, reading level, standardized test scores, absences) of cocaine-

exposed and control children.

Design: A total of 135 children (62 with gestational cocaine exposure and 73 without), who were enrolled at birth, followed prospectively

and have completed the fourth grade, were evaluated using report card data, standardized test results, teacher and parent report, and natal and

early childhood data. Successful grade progression was defined as completing grades 1 through 4 without being retained.

Results: Cocaine-exposed (cocaine-exposed presented first) and control children were similar in school performance: successful grade

progression (71% vs. 84%), Grade Point Average (2.4F0.8 vs. 2.6F0.7), reading below grade level (30% vs. 28%) and standardized test

scores below average (reading [32% vs. 35%], math [57% vs. 44%], science [39% vs. 36%]); all pz0.10. Children with successful

progression, regardless of cocaine exposure, had higher Full Scale Intelligence Quotient and better home environments.

Conclusion: In this inner-city cohort, cocaine-exposed and control children had similar poor school performance. Better home environment

and higher Intelligence Quotient conferred an advantage for successful grade progression, regardless of gestational cocaine exposure.

D 2004 Elsevier Inc. All rights reserved.

Keywords: Gestational cocaine exposure; Grade point average; School performance; Cocaine-exposed children; Inner-city

1. Introduction

Children with gestational cocaine exposure are at

increased risk for adverse neurodevelopmental outcome

[46,66]. Preclinical data from animal models demonstrate

cocaine effects on the fetus that range from marked

reduction in uterine blood flow [48] and fetal hypoxemia

[69], to effects on neuronal proliferation and connectivity

[50–52] to reduction in D1 receptor G protein coupling

[20,42]. Such cocaine-mediated effects on developing

dopaminergic circuitry, generally regarded as critical to

0892-0362/$ - see front matter D 2004 Elsevier Inc. All rights reserved.

doi:10.1016/j.ntt.2004.10.006

* Corresponding author. Hospital of the University of Pennsylvania,

Department of Neonatology-Ravdin 8th Floor, 34th and Civic Center Blvd.,

Philadelphia, PA 19104, United States. Tel.: +1 267 426 65110 or 215 662

4465; fax: +1 267 426 5201.

E-mail address: [email protected] (H. Hurt).

arousal regulation and attentional reactivity, are suggested

to impair attentional processes in exposed animals

[21,22,25,43,47,58] as well as humans [41,46]. These

effects, taken together, provide ample reason for concern

regarding exposed children’s neurodevelopmental and

cognitive outcomes. In particular, since the bepidemicQ ofcocaine use by pregnant women in the late 1980s, there has

been considerable national concern regarding anticipated

behavioral problems and poor academic performance by

children with gestational cocaine exposure [53,54,63]. With

concerns that all children with gestational cocaine exposure

would be pervasively developmentally delayed [54], there

were fears that such exposed children would be so delayed

or disruptive that traditional classrooms would be an

untenable situation for teaching [1]. More than a decade

later, there is a growing database regarding attentional and

behavioral outcomes in exposed children at school age

[3,56]; Richardson, in an assessment of children at age 6

ogy 27 (2005) 203–211

H. Hurt et al. / Neurotoxicology and Teratology 27 (2005) 203–211204

years who were born to women who reported only light to

moderate cocaine use during pregnancy, found no signifi-

cant effects of prenatal cocaine exposure on growth,

intellectual ability, academic achievement or teacher-rated

classroom behavior. She did find, however, that the

children exposed to cocaine exhibited deficits in ability to

sustain attention on a computerized vigilance task [56]. In a

report of school age behavior in children exposed

prenatally to cocaine, Delaney-Black found gender specific

behavioral effects related to prenatal exposure status, with

boys more likely to score in the clinically significant range

on the Achenbach’s Teacher Report Form (TRF). A number

of postnatal exposures, to include current drug use in the

home, exposure to violence and change in child’s custody

status were also associated with Teacher Report Form

scores [16]. More recently, Bandstra has reported severity

of prenatal cocaine exposure and language functioning

through age 7 years. She reports a cocaine-associated

deficit in aptitude for language performance but no

relationship between the severity of prenatal exposure and

the time-varying trajectory of language development [4]. So

far, however, few data [37] are available regarding the

school performance of exposed children. In a cohort of

inner-city children followed since birth, half with gesta-

tional cocaine exposure and half without, we report such

data for 135 children who have completed the fourth grade.

2. Methods

Participants are subjects enrolled in a prospective

longitudinal study of the effects of gestational cocaine

exposure. The children were enrolled at birth, half had

gestational cocaine exposure (COC) and half did not

(CON). Evaluations occurred semi-annually. In infancy

and early childhood, data were collected on the cohort’s

growth, development, language, behavior and cognition

[9,26–28,30–35]. When they reached school age, children

were also assessed for exposure to violence [36], school

performance [37], risk behaviors [38] and neurocognitive

status [29].

Mothers and newborn infants were recruited from a

single inner-city hospital over a three-year period from 1989

to 1991. At the time of enrollment, all mothers were of low

socioeconomic status, as defined by their receipt of medical

assistance. Mothers were ineligible for enrollment if they

did not speak English, had a major psychiatric disorder,

used drugs other than cigarettes, marijuana or alcohol, or if

they used cocaine in one trimester only. To separate the

effects of in utero cocaine exposure from that of prematurity

or birth asphyxia, infants were ineligible if they were less

than or equal to 34 weeks gestational age, or had a 5-min

Apgar of 5 or less. Infants were also excluded if they had a

syndrome known to be associated with adverse neuro-

developmental outcome such as Fetal Alcohol or Down

Syndrome. After chart review and structured interview,

mothers with a positive history for cocaine use were

classified as cocaine-using (COC). Mothers and infants

were classified as controls (CON) if mother had a negative

history for cocaine use, and urine samples from both mother

and infant were negative for cocaine metabolites on an

enzyme-linked immunoassay (Silva, San Jose, CA). The

status of participants was and has remained confidential,

known only to research coordinators; all examiners in this

study were masked to child exposure status. At the time of

enrollment, maternal consent was obtained; since child age

9 years, assent has been obtained from the children. The

Institutional Review Boards of Albert Einstein Medical

Center and The Children’s Hospital of Philadelphia

approved this study. All subjects were seen in a study

center in an inner-city hospital.

Two hundred twenty-four (105 COC and 119 CON)

subjects were enrolled at birth. During the ensuing years,

five subjects died (one CON and four COC), with an

additional attrition of approximately 39% of CON and 38%

of COC. The median days of in utero cocaine exposure for

cocaine-exposed children lost to follow-up was 64 days

compared with 99 days for children still active in the study

( p=0.20). Further, there were no differences in natal

characteristics between the 135 children with school data

reported on here (62% of the original cohort) and the 84

lost to follow up, except that more girls (68% of the

original 111 girls) than boys (53% of the original 113 boys)

have school data ( p=0.030). Cohort number, however, has

been stable now for the past 5 years, with 135 children (62

COC and 73 CON) comprising the sample for the current

report of school performance through the fourth grade.

Participants for this report are defined as those children for

whom we have data regarding pass/fail for grades 1–4. For

most children, we have additional school performance data

and, for the majority, we have additional data that has been

collected at visits conducted throughout middle childhood

and early adolescence, to include teacher and caregiver

appraisals, postnatal evaluations and assessment of the

home environment. Although some data for all these

variables are missing and some data were collected at

ages after completion of fourth grade, we elected to present

available data as they provide a more complete picture of

factors potentially associated with school outcome of

subjects. Because not every subject has had every

evaluation, the sample size for each evaluation is noted

below.

2.1. School measures

Data were obtained through cooperation with the

School District of Philadelphia. For those children who

are no longer in the district or who are not in public

school, we obtained grade progression data by caregiver

report. Grade status was defined as: (1) bpassQ, with the

child progressing to the next grade; (2) bretainedQ, with the

H. Hurt et al. / Neurotoxicology and Teratology 27 (2005) 203–211 205

child being required by school authorities to repeat the

grade; (3) bungradedQ, with the child being placed, by

school authorities, in special classes for social–emotional

disturbance or learning differences. Successful progression

was defined as child having passed grades 1 through 4

without being retained or placed in an ungraded class.

Grades, performance on fourth grade, school-administered,

Stanford-9 Standardized Achievement Test (SAT-9), school

absences and reading level were obtained from the child’s

school record. Grades were available for 108 children (51

COC and 57 CON), reading level for 104 (47 COC and 57

CON), days absent for 110 (51 COC and 59 CON) and

SAT-9 scores for 64 (28 COC and 36 CON). Grade point

average was calculated from the following schema: A=4,

C=2, F=0. TRF of the Achenbach System of Empirically

Based Assessment (ASEBA) [2] were requested annually

from each child’s teacher. The most recent form available

for each child (39 COC and 47 CON), from either grade 3

(n=10), grade 4 (n=61) or grade 5 (n=15), was used for

this report.

2.2. Child measures

Additional child measures included: (1) The Wechsler

Preschool and Primary Scale of Intelligence-Revised

(WPPSI-R) [67], administered at mean child age 6.1 years

(range 6.0–6.8) (103 children: 49 COC and 54 CON); (2)

Things I Have Seen and Heard (TISH) [45,57], an

interview for young children regarding exposure to

violence, administered at child age 7.5 years (7.2–8.1)

(60 children: 36 COC and 24 CON); (3) Culture-Free Self-

Esteem Inventories, Second Edition (CFSEI-2) [6] admin-

istered at age 7.1 years (6.9–8.3) (94 children: 42 COC and

52 CON); (4) Children’s Depression Inventory (CDI) [40],

administered at child age 10.9 (8.9–12.6) years (85

children: 39 COC and 46 CON); (5) Gordon Diagnostic

System (GDS) [23] a visual computerized test used to

measure impulsivity and sustained attention through three

tasks that posed conditions of increasing arousal/stress,

administered at age 10.3 years (9.8–13.0) (74 children: 39

COC and 35 CON). The GDS Delay Task’s Total Effi-

ciency Ratio assessed impulsivity (normal score z0.79).

The GDS Vigilance Task’s Total Correct (normal score

z42) and Total Commissions (normal score V4) scores

measured sustained attention and impulsivity, respectively.

The Distractibility Task’s Total Correct (normal score z32)

and Total Commissions (normal score V6) scores measured

sustained attention and impulsivity during distraction. The

Distractibility data for one cocaine-exposed child (reported

to have interrupted testing by moving about the room) was

removed as an outlier; (6) Trail Making Tests A and B

(Trails) [55], measuring visual attention and cerebral

efficiency, administered at child age 10.3 years (9.8–13.0)

(74 children: 39 COC and 35 CON); a normal score for

Trail A is V18 s, for Trail B V37 s.

2.3. Caregiver/environment measures

Measures focusing on the caregiver and home environ-

ment included: (1) The Child Behavior Checklist for Ages

4–18 of the ASEBA School Age Forms and Profiles [2] was

completed by the caregivers of 78 children (39 COC and 39

CON) at mean child age of 6.1 years (6.0–7.0); (2) the

Elementary School Version of Home Observation for

Measurement of the Environment (HOME) [15] was

administered in 91 homes (46 COC and 45 CON) at child

age 8.3 years (7.9–10.1); (3) caregiver urine specimens were

collected from 108 caregivers (49 COC and 59 CON) on

one or more occasions during child grades 1–4. A caregiver

was categorized as a current cocaine user if any of the

following criteria were met: (a) a positive screen at the time

the child was in grade 4; (b) the majority of screens over

time were positive; or (c) a current history of use by

caregiver report; (4) primary caregiver was defined at each

visit; because of complexities of multiple changes in

caregivers for some subjects, we analyzed caregiver data

for two groups: children always with their biologic mother

and children who were in foster care (kinship or other) at

any time (data available for all 135 children).

3. Results

Sixty-two COC and 73 CON have completed the fourth

grade at a mean age of 11.4 years (range 9.5–12.9). COC

had mothers who were older and had less prenatal care than

CON. At birth, COC were more likely to have been a

younger gestational age, exposed to cigarettes, alcohol and

marijuana, be admitted to the neonatal intensive care unit

and be discharged to foster care (Table 1). During the early

school years (Table 2), COC and CON were similar for most

outcomes. On the GDS, however, CON had a lower Delay

Efficiency Ratio than COC, although means for both COC

and CON groups were within the normal range. On the GDS

Distractibility Task, COC had higher Total Commissions,

suggesting a higher level of impulsivity than CON. Means

for both groups, however, placed them in the abnormal and

borderline ranges, respectively.

To determine whether any of the other in utero exposures

might be associated with differences in Distractibility, we

performed linear regression with backwards selection,

entering exposures to cocaine, cigarettes, alcohol and

marijuana. Only cocaine exposure predicted Distractibility

Commissions ( p=0.007). In addition, when Full Scale IQ

was also entered, the two significant predictors of Distract-

ibility were cocaine exposure ( p=0.033) and IQ ( p=0.009).

Caregivers of COC and CON reported similar child

behavior as measured by the CBCL. Girls and boys had

similar ratings, and there were no interactions between

exposure group and sex on any score in ANOVA analysis

(data not shown). Teachers, too, reported on the TRF that

COC and CON were similar in all aspects of behavior. In

Table 1

Maternal and natal characteristics of COC and CON at study entry

Characteristics COC, n=62 CON, n=73 p-value

Maternal

Age, years 27.1F4.8a 21.9F5.0 b0.001

African American, % 95 97 0.66

Education, years 11.3F1.5 11.7F1.2 0.12

Poor/no prenatal care, % 76 22 b0.001

Cocaine use in pregnancy, days 99b – –

Cigarette use in pregnancy, % 92 16 b0.001

Alcohol use in pregnancy, % 59 7 b0.001

Marijuana use in pregnancy, % 44 3 b0.001

Natal

Sex: female, % 48 62 0.16

Gestational age (GA), weeks 37.6F2.2 39.1F2.0 b0.001

Birth weight b10th %ile

for GA, %

8 3 0.25

Head circumference

b10th %ile for GA, %

16 11 0.45

Apgar score at 5 min 9b 9 0.66

Admitted to neonatal ICU, % 47 19 0.001

Abnormal cranial ultrasound

findings, %

3 6 0.68

Discharged to biologic

mother, %

87 100 0.002

a MeanFstandard deviation.b Median.

Table 2

Characteristics of COC and CON during early school years

Characteristicsa COC CON p-value

Wechsler Preschool and Primary Scale of Intelligence-Revised

Full Scale IQ 82.6F13.1b 84.2F12.9 0.55

Gordon Diagnostic System

Delay Efficiency Ratio 0.89F.11 0.80F.16 0.007

Vigilance—Total Commissions 10.1F11.5 8.4F11.4 0.53

Vigilance—Total Correct 38.0F7.5 36.5F10.2 0.50

Distractibility—Total Commissions 29.5F42.8 8.8F13.8 0.007

Distractibility—Total Correct 28.5F13.7 33.1F13.0 0.14

Trails

A—time (s) 32.4F11.2 29.6F13.6 0.33

B—time (s) 54.5F20.0 54.1F25.0 0.94

ASEBA-CBCL (parent)

Total Competence 42.0F9.8 42.1F9.2 0.96

Internalizing 42.5F8.8 44.7F10.2 0.30

Externalizing 44.8F10.6 45.0F11.7 0.94

Total Problems 41.6F11.1 42.6F11.6 0.70

ASEBA-TRF (teacher)

Total Adaptive 43.6F8.9 45.0F9.0 0.48




Any foster care, % 40 10 b0.001

HOME Total Score 44.1F5.7 47.5F3.9 0.001

Caregiver—current

cocaine use, %

45 7 b0.001

a Please see Section 2 for n for each evaluation.

Table 3

School performance of COC and CON

Characteristicsa COC CON p-value

Successful progression

grades 1–4

44/62 [71%] 61/73 [84%] 0.098

Grade 4 performance

Grade point averageb 2.4F0.8c 2.6F0.7 0.14

Reading below grade level

(%)

30 28 1.0

Stanford-9 Achievement Testd

Reading 41.6F16.7 41.7F16.5 0.99

Below Average, % 32 35 1.0

Math 34.2F16.6 39.4F17.5 0.23


Science 38.3F13.2 42.7F16.4 0.25


Days absent 13.5F10.7 13.8F11.5 0.89

a Please see Section 2 for n for each evaluation.b A=4, C=2, F=0.c MeanFstandard deviation.d Average range 34.4–64.9.


two-way ANOVA, however, boys, regardless of exposure

group, had higher Total Problem, Internalizing and External-

izing scores than girls (data not shown). There were no

interactions between sex and exposure group in any

comparison. COC and CON were similar on indices of

depression and self-esteem (data not shown). In regard to

environment, COC and CON were similar in exposure to

violence (data not shown) but COC were more likely to

have been in foster care, have lower HOME scores and have

caregivers currently using cocaine. Four CON caregivers,

who previously had had numerous negative urine screens,

had at least one positive urine screen during grades 1–4 of

their child’s schooling. Placing these children’s results in the

COC group did not alter the conclusions of any of the

analyses.

All measured aspects of school performance by COC and

CON were similar (Table 3). Although only 71% of COC

experienced successful grade progression, versus 84% of

CON, this did not reach statistical significance. Of children

with unsuccessful grade progression, three COC and no

CON were retained two or more times, and the number of

children placed in ungraded classes was similar in both

groups (data not shown). In addition, with COC and CON

taken together, 29% of children were reading below grade

level and one-third to one-half scored Below Average on

SAT-9 testing.

To better understand factors associated with poor school

performance, we compared characteristics of the 105

children with successful grade progression and the 30 with

unsuccessful progression, regardless of gestational cocaine

exposure (Table 4). Of the prenatal exposures, marijuana

was associated with unsuccessful progression. As expected,

WPPSI-R Full Scale IQ was higher in those children with

Table 5

Binary logistic regression model with successful school progression as

outcome

Variable B p Odds ratio (95% CI)

In utero cocaine exposurea �1.1 0.25 0.34 (0.06–2.15)

In utero marijuana exposurea 1.1 0.30 3.13 (0.36–27.2)

Any foster carea �0.55 0.56 0.58 (0.09–3.69)

Current caregiver cocaine usea �0.13 0.90 0.88 (0.11–6.78)

Total HOME score 0.17 0.026 1.19 (1.02–1.38)

Full Scale IQ 0.16 0.004 1.17 (1.05–1.30)

a Coding is yes=1, no=0.


successful progression. Better performance on the GDS

Vigilance and Distractibility Tasks and Trail B also was

associated with successful grade progression. Because

distractibility was associated with both school progression

and cocaine exposure, we sought to determine whether an

effect of cocaine on progression might be mediated through

its effect on distractibility. When distractibility was added to

the regression of cocaine exposure predicting progression,

there was only a small reduction in the coefficient for

cocaine; therefore, distractibility did not appear to be a

mediator. The high association between cocaine and

Table 4

Characteristics of children with and without successful progression in

grades 1–4

Characteristics Successful

progression,

n=105

Unsuccessful

progression,

n=30

p-value

Sex: female n=62 (59%)a n=13 (43%) 0.15

Prenatal exposures

Cocaine 61/105 (58%) 12/30 (40%) 0.098

Cigarettes 34/104 (33%) 7/29 (24%) 0.50

Alcohol 49/105 (47%) 20/30 (67 %) 0.064

Marijuana 17/104 (16%) 12/29 (41%) 0.009

Wechsler Preschool and Primary Scale of Intelligence-Revised

Full Scale IQ n=80 (76%)

86.8F10.9bn=23 (77%)

71.8F13.0

b0.001

Gordon Diagnostic System n=54 (51%) n=20 (67%)

Delay Efficiency Ratio 0.85F0.14 0.83F0.16 0.60

Vigilance—Total Commissions 7.7F7.2 13.6F18.1 0.047

Vigilance—Total Correct 38.6F8.4 33.8F9.2 0.038

Distractibility—Total Commissions 14.0F31.2 34.4F36.7 0.020

Distractibility—Total Correct 34.2F11.7 21.3F13.5 b0.001

Trails n=54 (51%) n=20 (67%)

A—time (s) 29.7F12.6 34.7F11.4 0.12

B—time (s) 49.8F23.7 66.5F11.9 0.004

ASEBA-CBCL (parent) n=61 (58%) n=17 (57%)

Total Competence 43.5F9.4 36.9F7.9 0.010




ASEBA-TRF (teacher) n=65 (62%) n=19 (63%)

Total Adaptive 45.9F9.1 39.4F6.1 0.001




HOME Total Score n=73 (70%)

47.0F4.1

n=18 (60%)

41.0F6.3

0.001

Any foster care n=20 (19%) n=12 (40%) 0.027

Current caregiver cocaine use 16/83 (19%)c 10/25 (40%) 0.059

a n and percent with characteristic or evaluation.b MeanFstandard deviation.c # and percent with z1 positive urine screen.

distractibility made testing of an interaction between the

two, and hence a moderating effect, unreliable.

On the ASEBA-CBCL, caregivers identified children

with successful progression (both boys and girls) as more

competent (Total Competence) than those with unsuccessful

progression (ANOVA, data for gender not shown). On the

ASEBA-TRF, teachers identified children (both boys and

girls) with successful progression as displaying more

constructive and prosocial behavior as measured by the

Total Adaptive score. Boys, however, exhibited more

internalizing behavior than girls, regardless of school

success (ANOVA, data not shown). As reported by teachers,

boys and unsuccessful students had higher Total Problem

scores, with no interaction exhibited. Children with suc-

cessful progression had higher Total Self-Esteem than those

with unsuccessful progression ( p=0.01) but were similar to

children with unsuccessful progression in indices of

depression and exposure to violence (data not shown).

The one environmental factor associated with successful

progression was higher Total HOME score.

To examine the simultaneous effects of environmental

factors and IQ on successful progression, we performed

logistic regression analyses with successful progression as

outcome. When exposure to cocaine and marijuana as well

as IQ, HOME score, any foster care experience and current

caregiver cocaine use was entered, only IQ ( p=0.004) and

HOME score ( p=0.026) were associated with successful

progression (Table 5). There was no evidence for either a

cocaine or marijuana effect. The odds of successful

progression were increased 2.2-fold (95% CI, 1.3–3.7) for

each 5 IQ points and 2.4-fold (95% CI, 1.1–5.0) for each 5

points of HOME score.

4. Discussion

In this inner-city cohort, children with gestational cocaine

exposure were less likely to have successful grade pro-

gression in grades 1–4 (71%) than were controls (84%);

however, this difference did not reach statistical significance.

Both groups, in fact, performed poorly, with 22% of the total

cohort experiencing grade retention once or more during the

first 4 years of school. Children with better home environ-

ments and higher IQs were more likely to have successful

grade progression regardless of gestational cocaine exposure.


The finding of similar school performance by COC and

CON was unexpected as the children with gestational

cocaine exposure in this cohort had not only risks suggested

by hemodynamic and cellular alterations noted in preclinical

models, but also risks attendant to mild prematurity, higher

incidence of admission to NICU, and in utero exposure to

poly-substance use by their mothers. Moreover, during the

early school years, the exposed children were also more

likely to be living in foster care, have a less positive home

environment and have caregivers currently using cocaine.

Because we found the groups similar in school performance,

we examined our study design for confounding factors that

may have masked significant differences between exposed

and unexposed children.

We considered the possibility that, at study entry, some

women who used cocaine were misclassified as controls.

This is possible; however, as we had negative history and

negative urine screens on both mother and baby, it seems

unlikely. Further, maternal profiles of the two groups were

quite different. Nevertheless, we cannot entirely exclude the

possibility that some women were misclassified. We also

considered that we might have enrolled women who were

not bheavyQ cocaine users. We doubt this as 88% of our

cocaine-using mothers had urines positive for cocaine

metabolites at delivery (data not shown) [28], a marker

suggested by Zuckerman et al. [70] to identify frequent

users. Further, we enrolled only women who used in two or

more trimesters of pregnancy, with 99% of our mothers

using in all three trimesters; the top quartile of self-reported

days of use in pregnancy in our cohort was 195 days or

more. Another potential etiology for the similarities between

groups could be attrition of more heavily exposed children.

In this regard, cocaine-exposed children lost to follow-up

were actually less heavily exposed than those children

retained (median days of exposure, 64 vs. 99, respectively).

An additional issue is sample size. Given the 13%

difference in grade retention rates shown here between COC

and CON, corresponding to a small to medium effect size,

and given the sample size available, the power to detect a

difference was only 41%. With the 13% observed difference

in retention rates between COC and CON, 161 children

would be needed in each group to reach statistical

significance. On the other hand, with the sample size we

have, COC retention rate would have to be 37% (a 21%

difference from CON retention of 16%), closer to a medium

effect size to reach statistical significance. It may well be

that results from a larger cohort or from a future meta-

analysis will show a significant difference. However, even if

statistically significant differences are found with a larger

sample, multivariate analyses will continue to be important

in assessing the additional influences of IQ and home

environment.

Finally, two additional issues merit consideration: first, it

may be that poverty, long linked with poor achievement

[7,12,39,49,59], obscured any group differences. In this

regard, we, as other investigators following similar cohorts,

have found low Full Scale IQ scores in both exposed and

unexposed children [8,32,35] and, second, measures of

school achievement, to include grade retention, simply may

be too general to show subtle effects of gestational cocaine

exposure.

Regardless, the overall poor school performance by both

groups taken together is concerning: by the fourth grade,

22% of the cohort experienced grade retention, 29% were

reading below grade level, and SAT-9 scores were below

average for 34% in reading, 50% in math and 38% in

science. While the racial composition and socioeconomic

status of our cohort limits generalizability of our results, we

have attempted to compare our cohort retention rates with

national data. These comparisons have proved somewhat

difficult as U.S. Census data are reported for students

babove age for gradeQ [62] and state practices vary. Some

data are available, however, from the National Household

Education Survey which reported 18% of Black, non-

Hispanic students repeated a grade in grades K through 12

[65], and The Chicago Longitudinal Study [62], which

reported retention rates of 28% between Kindergarten and

eighth grade for 1200, primarily African–American youth,

in an ongoing investigation of adjustment of low income

children. In neither case did we find data parsing retention

rates of urban, suburban and rural areas, or public and

private schools. Thus, while school performance of our

cohort is concerning, it seems similar to other inner-city

populations. Regardless, the high retention rate bodes

poorly for high school completion as The Chicago

Longitudinal Study reported a strong association between

grade retention and lack of completion of high school: one-

third of retained students completed high school compared

to 60% of students who were never retained. Further, with

repeated retentions, children overage for grade may become

disengaged from the school process, exhibit depressed

motivation and achievement and become more vulnerable

to risk behaviors. The impact of being overage for grade has

been described as being especially difficult for African–

American students [61].

As COC and CON had similar, poor, school perform-

ance, we elected to define characteristics that differentiated

those children with successful progression through grade 4

from those with poor progression. Because school age

outcomes are complicated by postnatal experiences [17],

both child and environmental factors were included in our

analyses. In univariate analysis, marijuana exposure was

associated with unsuccessful progression; however, this

effect was no longer present in multivariable analysis.

Analyses also showed the anticipated difference in

WPPSI-R Full Scale IQ, with higher IQ conferring an

advantage for successful progression. On tests of attention,

shown to be only moderately correlated with intelligence

[23], children with unsuccessful progression were more

impulsive, less attentive and less flexible, findings similar

to those reported in ADHD children [5]. Interestingly, in

our cohort, COC were also more distractible than CON,


raising the question of whether an effect of cocaine on

progression might be mediated through its effect on

distractibility. As stated in Section 3, however, the high

association between cocaine and distractibility made testing

of an interaction between the two unreliable in our cohort.

Regardless, this is an interesting area for future investiga-

tion. Children with poor progression also were more likely

to be perceived by teachers as having less constructive and

prosocial behavior than those children with successful

progression. We found it particularly interesting that

teachers identified increased problems in children with

unsuccessful vs. successful progression and, after stratifica-

tion for gender, in boys versus girls, but not in COC vs.

CON. This latter finding is in contrast to one report, in

which teachers did identify more problems in boys with

COC exposure [18].

In regard to caregiver ratings, caregivers of cohort

children reported similar behavior in children with success-

ful vs. unsuccessful progression, with the exception of lower

Competency in children with poor progression. Thus,

caregivers appear insightful regarding their children, but

we have no data regarding whether caregivers sought, or

were offered, interventions for their children.

Finally, while we did not examine teacher–child relation-

ships in this study, other investigators’ evaluation of

children from kindergarten through eighth grade have

reported that early positive teacher–child relationships were

important determinants of school success [24]. It follows

that children in our cohort with poor progression and

behavioral issues might also have had difficulty establishing

positive relationships in the classroom. Such a paucity of

positive relationships, in turn, could have affected develop-

ment of bschool connectednessQ[44], a factor considered

important for success in learning environments [71].

In both univariate and multivariate analyses, one

environmental factor, Total HOME score, was associated

with successful grade progression. A better home environ-

ment has long been correlated with higher intelligence test

scores, with measures as simple as providing cognitively

stimulating materials and experiences reported to confer an

advantage [10–14]. Improving the home environment as a

measure to raise IQ is receiving increasing support, with

data from adoption studies suggesting a strong influence of

home and socioeconomic status on IQ scores [10,19,60,68].

Recent work by Turkheimer et al. [64] is particularly

provocative. Using twin adoption studies, these investiga-

tors report that, while genes explain the majority of IQ

differences in children in wealthier families, environmental

factors explain differences in poor minorities: the impor-

tance of environmental influences on IQ was four times

stronger in poorer families than in families of higher

socioeconomic status. This discrepancy suggests a venue

to improve IQ and academic performance in children from

impoverished urban families.

Interventions to improve the home environment may

seem daunting. However, in an era replete with sophisti-

cated technology, costly treatments and genetic engineering,

offering developmentally stimulating materials and experi-

ences seems startlingly simple. Nevertheless, to improve the

outcome of inner-city children even the simplest interven-

tions require assumption of responsibility, focus and

commitment at a national level.

Acknowledgement

Supported by a grant from National Institute on Drug

Abuse #RO1-DA14129.

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