Published online February 1, 2007
PEDIATRICS Vol. 119 No. 2 February 2007, pp. e348-e359 (doi:10.1542/peds.2006-1404)
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ARTICLE

Impact of Prenatal Cocaine Exposure on Child Behavior Problems Through School Age

Henrietta S. Bada, MD, MPHa, Abhik Das, PhDb, Charles R. Bauer, MDc, Seetha Shankaran, MDd, Barry Lester, PhDe, Linda LaGasse, PhDe, Jane Hammond, PhDb, Linda L. Wright, MDf and Rosemary Higgins, MDf

a Department of Pediatrics, University of Kentucky College of Medicine, Lexington, Kentucky
b Research Triangle Institute International, Research Triangle Park, North Carolina
c Department of Pediatrics, University of Miami School of Medicine, Miami, Florida
d Department of Pediatrics, Wayne State University School of Medicine, Detroit, Michigan
e Department of Pediatrics, Brown University Medical School, Providence, Rhode Island
f National Institute of Child Health and Human Development, Bethesda, Maryland


   ABSTRACT
TOP
 ABSTRACT
METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
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.

Key Words: child behavior • prenatal exposure • cocaine • tobacco • alcohol

Abbreviations: PCE—prenatal cocaine exposure • MLS—Maternal Lifestyle Study • SES—socioeconomic status • HOME—Home Observation for Measurement of the Environment • BDI—Beck Depression Inventory • CBCL—Child Behavior Checklist • HLM—Hierarchical Linear Models

The "war on drugs" in the 1980s, the crack/cocaine epidemic, and the early reports on prenatal cocaine effects have created a public frenzy and a myth about the "dangerous" and "unfit to parent" women and their damaged "crack babies."1–3 States have continued the varying legal activities on policy decisions that affect women who use illegal drugs during pregnancy.4 Recent studies,3,5 however, have failed to support any association between prenatal cocaine exposure (PCE) and increased prevalence of newborn serious congenital malformations6,7 or medical complications.8,9 Therefore, studies have focused on determination of later effects of prenatal cocaine exposure on behavior and development.10,11 To date, reports on the effects of PCE on childhood behavior have shown conflicting results.12 Whereas some studies have evaluated a subpopulation from a cohort that was enrolled to determine outcomes from legal drug exposure,13,14 others have followed children with PCE but have not analyzed for multiple confounders, specifically other substances used with cocaine, life stresses, and parental health.14–17 Abnormal behavior has been associated with prenatal tobacco use,18–24 but longitudinal studies have not completely addressed the effect of antenatal tobacco in conjunction with postnatal tobacco exposure. Also, prenatal alcohol and marijuana exposures, both risk factors for childhood behavior problems,25–28 have not always been controlled for as part of the polydrug exposure that is common with cocaine use.29

PCE has been associated with abnormal neonatal neurobehavior30 by clinical assessment or by administration of neurobehavioral scales.31,32 Prenatal cocaine has been reported also to have a modest effect on IQ.10 Therefore, it is important to determine whether behavior problems among exposed children have an effect on later school achievement or when cognitive demands increase.15 The trajectory of long-term behavior problems after PCE has not been characterized. Therefore, we determined the behavior outcomes of children through school age after gestational cocaine exposure. We hypothesized that PCE is associated with long-term childhood behavior problems.


   METHODS
TOP
 ABSTRACT
 METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
The Maternal Lifestyle Study (MLS) is a longitudinal cohort study to evaluate long-term outcomes of children who are prenatally exposed to cocaine in 4 collaborating sites: Brown University (Providence, RI), University of Miami (Miami, FL), University of Tennessee (Memphis, TN), and Wayne State University (Detroit, MI). The Research Triangle Institute (Research Triangle Park, NC) and Brown University, respectively, serve as the Statistics-Data Coordinating Center and the Neurobehavioral Battery Coordinating Center. Each participating center had approval for the study from the institutional review board and had a certificate of confidentiality from the National Institute on Drug Abuse. Informed consent was obtained from all participants.

Mother–infant dyads were enrolled at each hospital within 24 hours after delivery between 1993 and 1995 (phase 1).5,33,34 Mothers were asked to consent to an interview regarding drug use during pregnancy and to a toxicologic analysis of their infant's meconium. Exposure was determined separately for cocaine and opiates on the basis of a mother's admitting cocaine/opiate use during pregnancy and/or a positive meconium assay for cocaine or opiate metabolites. Nonexposed children were those who were born to mothers who denied cocaine and opiate use, confirmed by negative meconium test results. From the exposed children in phase 1, we derived a cohort for longitudinal follow-up that was matched within site with a group of nonexposed children by gestational age categories (<32 weeks, 33–36 weeks, and >36 weeks) and child's gender, race, and ethnicity. The details of the follow-up (phase 2) selection procedure have been reported.31,35

Enrolled children were assessed at the first clinic visit at 40 to 44 weeks' postmenstrual age, and then yearly for evaluation of health, motor, mental, and behavior outcomes. At the first visit, each mother was interviewed for a detailed inventory of her legal and illegal drug use during pregnancy. Prenatal cocaine use was categorized into high, some, and none. High cocaine use referred to ≥3 times per week in the first trimester.31,36 Any other use was referred to as some cocaine use. Our previous studies31,37,38 reported on similar definitions for the levels of cocaine use. At each subsequent visit, the child's caregiver also was interviewed for ongoing use of cocaine, opiates, marijuana, tobacco, and alcohol (yes or no); experience of physical and or sexual abuse (yes or no); and child's living situation or caregiving status (child with biological mother or other caregiver). We also asked about income and occupation for each member in the household, from which we derived a measure of socioeconomic status (SES) using Hollingshead Index of Social Position.39,40 Assessment of the home was done using the Home Observation for Measurement of the Environment (HOME)41 during a home visit between 5 and 6 years of age. The Beck Depression Inventory (BDI) was administered at the 7-year visit as a proxy for caregiver psychological distress or functioning.

Behavior problem outcomes were determined from the Child Behavior Checklist (CBCL),42,43 which was administered at ages 3, 5, and 7 years. The CBCL was administered verbally by a trained research interviewer to ensure uniform administration across sites to all caregivers regardless of literacy level. From the summary scores, we derived the T scores for outcomes and internalizing, externalizing, and total behavior problems using a computer scoring system.44,45

The CBCL provides a profile of the child's social and behavioral functioning relative to children of the same age and gender. Internalizing problems include social withdrawal, somatic complaints, and anxiety/depression. Externalizing problems include delinquent and aggressive behaviors. The CBCL also includes scales for social, thought, and attention problems that are not categorized as either internalizing or externalizing problems but are included in the total behavior problems.

Statistical Methods
The t test was used to compare means for continuous variables, whereas the {chi}2 test was used to compare proportions for categorical variables. Mean behavior problem scores for each visit were compared according to levels of cocaine and other prenatal drug exposures, using analysis of variance for 3 levels of exposure and t tests for binary (yes/no) exposure. Longitudinal analyses using Hierarchical Linear Models (HLM)46 were used to determine the trajectory of behavior problems from 3 to 7 years of age across levels of cocaine exposure while controlling for confounders. The problem scores (as continuous variables) at different time points were used in the HLM approach to model the trajectory of each behavior outcome (ie, behavior problems scores) as a function of PCE and other covariates and confounders.

A priori, we always adjusted for the following covariates regardless of statistical significance: prenatal exposure to opiates (yes/no), alcohol (average of absolute alcohol per day), tobacco (average number of cigarettes per day), and marijuana (average number of joints per day), study site, and gender. We further adjusted for other covariates only when the P value overall or for any category was ≤0.1 or when the inclusion of the variable substantially changed the relationship between PCE and the outcome. These variables included race, maternal age, the HOME score,41 and caregiver depression (BDI). In addition, we adjusted for time-varying covariates that were obtained at each assessment at 3, 5, and 7 years (caregiver use of tobacco, alcohol, and marijuana; report of physical/sexual abuse as a family violence measure; and SES). Postnatal caregiver use of cocaine and opiates were too rare to include meaningfully in our analyses. There were 3.3% and 13.6% missing values for the HOME and the BDI, respectively; therefore, for these 2 covariates, we used multiple imputation, as implemented in the Sequential Regression Imputation Method of Raghunathan et al.47

Birth head circumference and child's living situation, being competing outcomes of PCE, were analyzed as mediators of the relationship between exposure and long-term behavior outcome using the methods developed by Baron and Kenny.48 Children with PCE were likely to be with a caregiver other than the biological mother, and49 from our earlier report and others,50–52 PCE was associated with a decrease in head circumference. Of the growth measurements, head circumference was chosen for its high correlation with brain growth. Also, PCE was reported to exert its effect on preschool development as mediated through head circumference.53


   RESULTS
TOP
 ABSTRACT
 METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
In phase 1 of the MLS, 11811 mothers consented to enrollment in the study. Meconium was unavailable or of insufficient quantity for analysis in 3184 infants.5,34 From the remaining 8627, we derived the population for the longitudinal study (phase 2). The characteristics of the individuals who were not selected or enrolled in phase 2 are shown in Table 1. Because of the way we derived our longitudinal cohort sample from the larger phase 1 sample (ie, those who were exposed were matched with a sample of nonexposed), most sociodemographic and other characteristics, by design, are significantly different between these 2 groups.


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  		TABLE 1 Characteristics of Phase 1 Dyads That Were Not Selected or Enrolled in Phase 2 and the Comparison of Dyads Who Had Follow-up and Those With No Follow-up in Phase 2

 
The longitudinal follow-up sample comprised 1388 children (543 PCE, 58 opiate only, 57 PCE + opiate, and 730 nonexposed). Characteristics of these groups at enrollment were published previously.31,35 The exposed group had higher proportions of mothers who were single and who were older than 25 years than the nonexposed group. More mothers who used cocaine had Medicaid insurance and had education <12 years compared with those who did not use cocaine. Of the 1388 enrolled, 1056 (76%) had CBCL administered in at least 1 visit and had known levels of PCE exposure. Table 1 compares this group with the 332 (24%) without CBCL. The proportions of cocaine and opiate exposures were higher in those with no follow-up as compared with those with follow-up assessment. However, the proportion of high PCE exposure did not differ between the 2 groups.

Prenatal Exposures (Unadjusted Analyses)
Table 2 shows the mean (SD) total, internalizing, and externalizing behavior problem scores at 3, 5, and 7 years by high, some, and no PCE and by categories of each type of prenatal drug exposure. Mean internalizing, externalizing, and total behavior problem scores increased with levels of PCE. Prenatal tobacco exposure had a significant effect on behavior outcomes at ages 5 and 7 years. Prenatal alcohol also had a negative effect on behavior outcomes; its effect became more significant at later ages. Prenatal marijuana influenced externalizing and total behavior problem scores only at 5 and 7 years. Prenatal opiate exposure affected externalizing behavior problems only at 5 years.


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  		TABLE 2 Behavior Problem T Scores at 3, 5, and 7 Years According to Prenatal Drug Exposure

 
Prenatal and Postnatal Exposures (Adjusted Longitudinal Modeling)
The results from longitudinal HLM analysis for each behavior outcome are presented in Table 3. After controlling for confounders including other drug use, we found that high PCE was associated with higher behavior problem scores compared with some or no cocaine use during pregnancy, with a significant effect persisting to 7 years. The trajectories for these behavior outcomes across different levels of PCE (adjusted for other confounders included in the model) are shown in Figure 1. Note in the figure as well that the predicted behavior problem scores for the nonexposed are higher than T score mean of 50 that was reported for the general population.54


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  		TABLE 3 Selected Results From Longitudinal Analyses Using HLM for Outcomes: Internalizing Problems, Externalizing Problems, and Total Problems T Scores

 

Figure 1
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  		FIGURE 1 Predicted scores for internalizing (A), externalizing (B), and total behavior (C) problems according to levels of PCE, obtained from the fitted longitudinal models. These fitted values are adjusted for all covariates included in these models. Note that mean scores for internalizing behavior problems show a decrease at 5 years and then increase in the subsequent years. The predicted mean scores for externalizing and total behavior do not differ over time. Note as well that the differences in mean scores between high PCE and no PCE for the behavior problem scores are of similar magnitude over time.

 
Similarly, prenatal tobacco and alcohol exposures were significantly associated with total behavior problem trajectories through 7 years of age, with a significant dosage–response relationship (ie, higher behavior problem scores were associated with greater average number of cigarettes per day and greater average volume of alcohol per day). Prenatal opiate exposure had a significant effect only on externalizing behavior at 5 years of age. Prenatal marijuana exposure no longer was significant after confounders were controlled for. Postnatal caregiver use of marijuana did not influence the behavior outcome trajectories, but ongoing tobacco and alcohol exposures significantly affected externalizing and total behavior problems.

There were no gender differences in internalizing behavior problem scores at 3 years, but boys had higher scores in later years. Gender did not have an effect on externalizing (P = .63) or total behavior problems (P = .15). Higher SES was associated with lower internalizing behavior problem scores; this effect decreased over time. Younger maternal age at child's birth was associated with higher behavior problem scores, with its effect decreasing over time for internalizing behavior. Caregiver report of physical or sexual abuse and caregiver depression were significantly associated with all behavior problems. HOME score was marginally related to externalizing behavior (P = .057). As to living situation, 16%, 23%, and 21% of children were not living with their biological mother at 3, 5, and 7 years, respectively. Mediation analysis (Fig 2A, B, and C) revealed that the child's living situation (P < .05) but not head circumference was a significant mediator for the relationship between PCE and behavior outcomes.


Figure 2
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  		FIGURE 2 A, Mediation effects of birth head circumference and child's living situation or arrangement for the relationship between PCE and CBCL internalizing scores at 3 to 7 years of age. (a) shows the direct relationship between cocaine and outcome; (b) and (c) show the relationship between cocaine and each mediator, as well as between cocaine and the outcome, adjusting for each mediator; and (d) shows the relationship between cocaine and the outcome, adjusting for both mediators simultaneously. B and C, Similar mediation effects for externalizing and total behavior problems, respectively. Numbers presented are regression coefficients/odds ratios from appropriate models (longitudinal model for exposure->outcome, adjusting for temporal effects; linear regression model for exposure->birth head circumference, and logistic regression model for exposure->living situation). Effects of high cocaine exposure are bolded. * P < .05 (overall F test P value used for 2-level cocaine effect)

 

   DISCUSSION
TOP
 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
Our findings add credence to the reported association between PCE and childhood behavior problems,13,16,17 an association that is independent of the effects of other prenatal and postnatal drug exposures and other confounders. Results of our longitudinal analysis indicate not only sustained but also greater effects with higher levels of PCE on the trajectory of childhood behavior problems. Our results further suggest a dosage–response relationship between exposure and behavior problems. Also, prenatal tobacco and alcohol exposures have significant long-term effects on behavior problems through 7 years of age; these long-term effects are compounded by continued postnatal exposure to these substances.

Interpretation of Effect Size
Our observed adjusted cocaine effects on the CBCL scores are significant in a clinical context (where remedial action usually is taken only when such scores fall within a referral or deviant behavior range). Given that the CBCL score is normed to a mean (SD) of 50 (10) for the general population and rounding our observed cocaine effect sizes to 2 points for internalizing and 3 points each for both externalizing and total behavior problem scores, we can infer the following from these results: a 2-point mean upward shift in the distribution of the CBCL internalizing score as a result of heavy PCE would result in a 31% increase (from 16% to 21%) in the prevalence of children with scores in the referral/deviant behavior range (≥60) at 3 to 7 years of age. Similar increases for the externalizing and total scores are at 50% (from 16% to 24%) each. Results from our calculation of effect size suggest that the combined effect of prenatal and postnatal tobacco and alcohol exposures on externalizing behavior (4.6 points) in fact is greater than the effect of PCE alone (3.1 points). This holds true for both internalizing and total problem scores and for all ages.

PCE and Childhood Behavior
A review on the association between PCE and early childhood behavior revealed conflicting findings.12 Few studies determined outcomes beyond 3 years of age,55,56 and none evaluated the trajectory of behavior outcomes.13,16,55,57–59 Some studies reported on outcomes on a subpopulation of a cohort that was followed longitudinally primarily for exposure to other drugs, not to cocaine.13,16,17,57 Also, methods for behavior assessment differed among studies.

Earlier studies found higher externalizing behavior scores in children with PCE than in control subjects at 3 years of age; this effect of PCE persisted even after controlling for other factors.60,61 Another study, in older children, observed that exposure to prenatal cocaine and other drugs had a direct effect on child behavior characteristics62; those who were exposed had higher behavior problems scores than those with no PCE. However, other studies noted no association between PCE and child behavior problems or between levels of PCE and behavior outcomes.59,63 The effect of PCE seemed to be moderated by gender and prenatal alcohol exposure. Sood et al64 reported an association between PCE and delinquent behavior in boys with prenatal alcohol exposure and an association between PCE and aggressive behavior in girls but only in the absence of prenatal alcohol exposure. Another study,65 using the teachers' assessment of child behavior, found that boys with PCE were twice as likely to have externalizing behavior than control subjects, but no such effect was noted in girls. We found no gender effect on externalizing behavior problems, even after controlling for other prenatal drug exposures, but we derived our results from caregiver rather than teacher report.

On the basis of teachers' assessment of behavior, PCE was a significant factor associated with manifestation of low anxiety and high externalizing behavior problem scores.13 School-aged children with PCE had more problematic behavior such as hyperactivity, distractibility, unpredictability, and attention problem compared with nonexposed children.16 Of these problems, only attention problem was noted to be statistically significant.16 Leech and colleagues,17 using a continuous performance task in 6-year-old children, noted impulsivity and inattention with PCE and further noted that first-trimester cocaine exposure predicted inattention. Another study that used a similar measure showed a stable PCE-specific effect on sustained attention processing; those with PCE had significantly increased omission scores.66 Impaired attention behavior could affect visual motor processing and procedural learning, which are required for cognitive functioning.67–70 Although inattention was not analyzed specifically in our study, attention problems were included in the total behavior problem scores, which were significantly associated with PCE.

PCE, Child Behavior, and Psychosocial Issues
Some follow-up studies on children with PCE found that child behavior problems and mental health were related to caregiver psychological mental functioning or distress, caregiver depression,55,63 interaction between caregiver and the child,71 and caregiving status.72,73 We found caregiving status or the child's living situation to be a mediator of the effect of PCE on child behavior problems. We also found behavior problems to be related to caregiver psychological distress and to family violence, on the basis of continuing caregiver report of physical or sexual abuse. These findings were in keeping with the report of Linares et al,73 who found significant correlation between family aggression and maternal distress in the path to childhood behavior problems. Other investigators also found a relationship between child behavior problems and community violence, as well as mother's and child's witnessing of violence.73–75

Chronic poverty and highly disadvantaged neighborhoods have been reported to have significant effects on children's mental health.76,77 Lower SES as a time-varying covariate in our study was associated with higher internalizing behavior problem scores. Lower SES and HOME scores, together with PCE, possibly reflected less availability of family or home resources and the quality thereof.

The lack of significant effect of PCE on head circumference possibly could be explained by our use of gestational age as a matching criterion for deriving the phase 2 longitudinal sample from the larger baseline phase 1 sample. Because gestational age is highly correlated with birth growth measurements, its balanced distribution across exposure groups may have precluded our ability to observe a significant PCE effect on head circumference. Other investigators, however, found head circumference to be a significant mediator of the effects of PCE on cognitive functioning.53,60

Effects of Prenatal Opiate and Marijuana
We found a prenatal opiate exposure effect on externalizing behavior problems only at 5 years; the number of opiate-exposed children in our study may have been too small to detect sustained significant effects. After controlling for other factors, we found no significant effects from prenatal marijuana. However, other investigators reported significant association between prenatal marijuana and hyperactivity, impulsivity, inattention, delinquency, and externalizing behavior.26,78 With continuing follow-up, we may detect the effects of marijuana at a later age.

Effects of Prenatal and Postnatal Alcohol Exposures
Our finding of a dosage–response effect of prenatal alcohol exposure on externalizing and total behavior problems is consistent with the report of others.28 A concern is our finding of an additional effect of the caregiver's continuing alcohol use. Although direct toxic effect is unlikely with postnatal alcohol exposure, continuing caregiver use may represent a marker for an environment with caregiver psychological distress, household chaos, and victimization79; alcohol abuse is a major problem in families who are investigated for child maltreatment.80

Effects of Prenatal and Postnatal Tobacco Exposures
Smoking during pregnancy was associated with toddler negativity,81 externalizing behavior problems, internalizing behavior,24 aggression, conduct disorder,21 oppositional defiant behavior, criminal behavior, psychiatric morbidity,20 and attention-deficit/hyperactivity disorder.18,23,81 However, these findings were drawn from case-control82 and cohort studies20,24 that determined outcomes from cross-sectional analysis and not from repeated evaluations, which are necessary to characterize the trajectory of behavior problems. Also in our study, the effect of prenatal tobacco on behavior problem trajectory suggested a dosage–response relationship.

Few reports suggested an association between behavior abnormalities and postnatal tobacco exposure.19,83 Among 10-year-old children who were assessed for impulsivity, current tobacco use was a more significant factor than prenatal exposure.23 One study reported a higher rate of externalizing behavior problems in 5-year-old children with both prenatal and postnatal tobacco exposures than with prenatal exposure only.20 From our results, postnatal tobacco exposure had a negative impact on child behavior independent of the effect of prenatal exposure. Continuing caregiver use of tobacco likely could expose the child's developing brain to the effects of nicotine and other toxins through passive inhalation; exposure to environmental smoke may affect cognitive outcomes in children.83,84

Study Strengths and Limitations
The relatively large sample size of the MLS with individuals who were recruited from a diverse population combined with our high retention rate enabled us to control for multiple confounders, including other prenatal and postnatal drug exposures, caregiver depression, and other family and environmental factors. With repeated outcomes determined through 7 years of age, we found a significant and sustained effect of PCE on the trajectory of childhood behavior problems and noted a suggestion of a dosage–response relationship. To our knowledge, this is first report of the effect of PCE on the trajectory of child behavior problems through school age. Although our analysis is an important step in examining the relationship between PCE and behavior outcomes, causality is far from being established. It is hoped that our study results would guide scientists in continuing to explore the underlying mechanisms of the effects of cocaine on the developing brain to explain these associated behavioral alterations.85–87 Animal studies will need to consider principles that are pertinent to evaluation of cause-and-effect relationship such as the timing of exposure, the appropriate time in development when outcomes are noted, and conditions that may alter effects or outcomes after prenatal cocaine exposure.87

We recruited our subjects from hospitals in the inner city and high-poverty neighborhoods; this limits the generalizability of our findings. Consistent with this is our finding that nonexposed children had higher mean problem scores than the general population.54,88 Although we used biological measures for classification of cocaine exposure, we relied on self-report for categorization of levels of prenatal exposure to cocaine, tobacco, and alcohol and for determination of postnatal drug exposures. Therefore, our findings may represent either underestimation or overestimation of drug exposure effects. We were unable to determine the effects of postnatal cocaine because of the rare postnatal use of cocaine in our study; a number of children with PCE had primary caregivers other than their cocaine-using mothers. Although we included the BDI in our analysis, we had only a proxy measure for caregiver's mental health. Furthermore, we did not evaluate the buffering effects of maternal–child relationship as a mediator on the influence of violence on child behavior outcomes.75 We also did not control for other potential confounders, such as genetic predisposition, interaction between genes and environment, heritable tendency to mental illness,89–91 maternal comorbidities, language delay or impairment,92,93 and community violence; these factors may be associated with child behavior outcomes. Because we continue to follow our cohort, we will be able to address additional measures in the home and environment that may affect child behavior. We also will be evaluating child behavior from the teachers' perspective and therefore we will be able to compare our findings with those of investigators who evaluated child behavior from teachers' report.

Practice, Public Health, and Policy Implications
Prenatal and postnatal exposures to tobacco and alcohol are of significant public health concern. Their combined effect on child behavior is greater than what can be attributed to cocaine. Therefore, our findings highlight not only a need for continued prevention and treatment programs that are directed toward illegal drug use but also a call for increased effort toward prevention of tobacco and alcohol use, which is a more prevalent problem and has as great an impact on childhood behavior problems as PCE. Furthermore, in the evaluation of a child with behavior problems, in addition to information on prenatal and postnatal drug exposures, the possible influences on behavior of caregiver mental health and adverse factors in the home or environment must be examined because these risks add to the effects of drug exposures.


   ACKNOWLEDGMENTS
 
This study was conducted with support from the National Institutes of Health National Institute of Child Health and Human Development through cooperative agreements and interagency agreement with the National Institute on Drug Abuse; Administration on Children, Youth and Families; and Center for Substance Abuse Treatment. Participating institutions, grant awards, investigators, and key research personnel include the following: Brown University, U10 HD 27904, N01-HD-2-3159 (Barry M. Lester, PhD, Cindy Loncar, PhD, Linda LaGasse, PhD, and Jean Twomey, PhD); University of Miami, U10 HD 21397 (Charles R. Bauer, MD, Wendy Griffin, RN, and Elizabeth Jacque, RN); University of Tennessee, U10 HD 21415 (Henrietta S. Bada, MD, Charlotte Bursi, MSSW, Marilyn Williams, MSW, Deloris Lee, MSW, Lillie Hughey, MSW, and Kimberly Yolton, PhD), Wayne State University, U10 HD 21385 (Seetha Shankaran, MD, Eunice Woldt, MSN, and Jay Ann Nelson, BSN); RTI, International, U01 HD 36790 (W. Kenneth Poole, PhD, Abhik Das, PhD, and Jane Hammond, PhD); and National Institute of Child Health and Human Development (Linda L. Wright, MD, Rosemary Higgins, MD); and National Institute on Drug Abuse (Vincent L. Smeriglio, PhD).


   FOOTNOTES
 
Accepted Aug 21, 2006.

Address correspondence to Henrietta S. Bada, MD, MPH, University of Kentucky Chandler Medical Center, 800 Rose St, Room MS 477, Lexington, KY 40536. E-mail: hbada2{at}uky.edu

The authors have indicated they have no financial relationships relevant to this article to disclose.


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 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
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