Abstract
Objectives
Three groups of children from low-income, urban environments were examined to determine the effects of prenatal drug exposure (PDE) and caregiving environment on sustained visual attention (SVA) at 7 years of age.
Methods
Drug-exposed children remaining in maternal care (n = 43), drug-exposed children placed in nonmaternal care (n = 45), and community comparison (CC) children (n = 56) were administered a battery of neurocognitive tests, including the Conners’ Continuous Performance Test (CPT).
Results
PDE children remaining in maternal care displayed more omission errors than CC children. PDE children in nonmaternal care had intermediate scores that did not differ significantly from PDE children in maternal care or CC children. There were no group differences with respect to commission errors or reaction time. CPT errors of omission and commission were significantly correlated with parent-reported attention problems and academic achievement scores.
Conclusions
PDE in the context of care provided by a maternal caregiver with persistent drug use patterns may contribute to problems in children’s SVA at school-age. As parental drug abuse can interfere with the provision of early care, children raised in a drug-using context may be highly vulnerable to problems with self-regulation, including sustained attention. SVA problems may contribute to subsequent academic and behavioral problems as demands for concentration and sustained effort increase throughout childhood. Children who have been prenatally exposed to drugs or raised in a drug-using household may benefit from early intervention services to avoid problems in SVA that may interfere with subsequent neurocognitive functioning and academic performance.
Index terms: sustained visual attention, prenatal drug exposure, Conners’ CPT
Studies examining links between prenatal drug exposure (PDE) and children’s neurocognitive development have produced mixed findings. In early childhood, difficulties have been documented in language development, arousal regulation, and attentional functioning after exposure to commonly abused drugs, such as cocaine and heroin.1 By school-age, however, many of the associations between PDE and neurocognitive outcomes are attenuated when postnatal environmental factors are included in statistical models.2,3 These findings are not surprising given the critical role of caregiving in children’s cognitive and behavioral development.4 Only recently have studies begun to emphasize the importance of environmental confounds, such as poverty, prenatal exposure to tobacco and alcohol, growth indicators, and variations in caregiving when evaluating how PDE influences children’s neurocognitive functioning.5–8 Thus, PDE is a risk factor not only for neurocognitive problems, but also for environmental challenges that can adversely affect children’s development.9
There has also been a methodological shift away from a reliance on global assessments in favor of targeted neurocognitive outcomes. PDE-related differences in intelligence quotient and global development are often attenuated after accounting for environmental factors.6,7,10 The few studies that detected exposure-related differences beyond the preschool years examined specific neurocognitive domains such as language, attention, and self-regulation.11–15 Each of these domains is critical for learning and social interactions.
Among school-aged children exposed to cocaine or heroin in utero, a consistent finding is that PDE leads to suboptimal performance on tasks of sustained attention.5,13,14,16–19 Several mechanisms are thought to link deficits in attentional functioning to PDE. Cocaine and heroin cross the blood-brain barrier in the developing fetus.20 Both substances can permanently alter dopaminergic and noradrenergic pathways in the developing brain,21–23 and these pathways play a role in regulating attention.24 PDE may also impair neuronal migration and disrupt brain cell proliferation,25 which can subsequently interfere with performance on frontally mediated neurocognitive tasks.26 Distractibility and disrupted arousal regulation have been documented as early as infancy in children prenatally exposed to cocaine and heroin.21,27
Despite an accumulation of data from studies with young children indicating that PDE is associated with sustained visual attention (SVA) deficits, the precise nature of these deficits remains unclear. Several studies have found that PDE is associated with inhibitory control problems on various neurocognitive measures.7,13,14,18,28 Others have found that PDE is associated with slow and variable reaction time and an inattentive response style.5,12,19 Problems with SVA can adversely affect children’s ability to concentrate, process information efficiently, and retain information for later recall, suggesting that such deficits are clinically meaningful.
PDE may contribute to neurocognitive deficits directly through teratogenic effects, but also indirectly through environmental conditions that disrupt the development of self-regulatory skills necessary for adequate attentional functioning.21 For example, drug-using mothers are more likely to present with comorbid mental health problems, less likely to provide sensitive care or supervision to their children, less likely to provide effective discipline, and are at higher risk to lose custody of their children than non–drug-using mothers.29,30 Co-occurring risk factors of PDE such as poverty, low caregiver intellectual functioning, and ongoing maternal alcohol, tobacco, and drug use also likely contribute to neurocognitive deficits in children with a history of PDE who continue to live in parental care.6,9 Although some studies have found that out-of-home placements contribute to difficulties with inhibitory control in young children,31–33 children raised in nonparental care may experience a more sensitive and stimulating cognitive environment than children who remain in the care of a substance-abusing caregiver.
This study examines how PDE and postnatal environmental conditions are related to children’s SVA at 7 years of age. We test three hypotheses: (1) Children with a history of PDE perform more poorly than nonexposed children on SVA, controlling for relevant demographic and environmental factors. (2) Among children with a history of PDE, those who remained in maternal care perform more poorly on SVA than children placed in nonmaternal care. (3) Performance on a computerized task of SVA is associated with academic achievement and caregiver-reported attentional skills.
METHOD
Study Design and Participants
Participants were part of a longitudinal randomized, controlled trial of a home-based intervention among drug-using women and their infants approved by the University’s Institutional Review Board.34 Women were recruited from a University Hospital serving a predominately inner-city, African-American population. Women were eligible for recruitment if they or their infants had a urine toxicology screen at birth that was positive for cocaine or heroin or a self-reported history of cocaine or heroin use during pregnancy (≥2x/wk). Eligibility criteria included gestational age ≥32 weeks, birth weight ≥1,750 g, and no medical complications requiring admission to the neonatal intensive care unit.
Two-hundred and sixty-five mothers agreed to participate and kept a baseline 2-week appointment. At the baseline visit, perinatal data were collected from the infants’ medical chart and the Addiction Severity Index (ASI)35 was administered to determine the duration and frequency of drug use during pregnancy. Mothers were randomly assigned to a home intervention or control group. Families in the intervention group received developmentally oriented home visits for 1 year, based on the program used by the Infant Health and Development Program.36 Families in the control group received monthly tracking visits. All families were assessed at 6-month intervals by trained research assistants blind to participant drug-exposure or intervention status. Families were also given information on drug treatment programs and were compensated for each evaluation.
At 7 years of age, 128 child/caregiver pairs of the original 265 were available for assessment. Causes of attrition were child deaths 8 (3%), foster care placement 37 (14%), moved out of state 6 (2%), and family could not be located or withdrew from the study 87 (33%). There were no attrition differences in neonatal characteristics, maternal drug use, urine toxicology, or other demographic variables.
Among the 128 children in the prenatal drug exposure (PDE) group, 32.8% had a positive infant or mother toxicology screen for cocaine only, 14.1% were positive for heroin only, 30.5% were positive for both cocaine and heroin, 10.1% did not have a positive toxicology screen, but self-reported frequent cocaine or heroin use during pregnancy (>twice/wk), and 12.5% were excluded from analyses, because mothers reported infrequent drug use during pregnancy and did not have a positive toxicology screen for cocaine or heroin (n = 16).
Seventy participants from a non–drug-exposed community cohort (CC) group served as a community standard for comparison. They were recruited from a primary care clinic serving the University Hospital when they were 5 years old. Medical records were reviewed to identify children delivered at the University Hospital at the same time as children from the PDE group, both the mother and infant had negative toxicology screens, and there was no history of drug use in the mother’s medical records. Participants resided in the same community as participants in the PDE group and were matched for socioeconomic status, age of first pregnancy, gender, and race. At 7 years of age, 61 child/caregiver pairs from the CC group were available for assessment and all children in the CC group resided with their birth mother.
Child Measures
Conners’ Continuous Performance Test
The Conners’ Continuous Performance Test (CPT) assesses sustained visual attention (SVA) or the ability to discriminate between target and nontarget stimuli presented at variable intervals.37 The CPT was completed on an IBM-compatible desktop computer in our clinical laboratory. Standard administration of the CPT consisted of 360 letters, which appeared on the computer screen, one at a time, for approximately 250 ms. Trials were presented in 18 blocks of 20 trials each. The 18 interstimulus interval (ISI) blocks consisted of a separate block-randomized ISI (1, 2, or 4 sec). Participants were required to press the spacebar when any letter except “X” appeared on the screen. The task took approximately 14 minutes to complete. The Conners’ CPT was selected because of its potential sensitivity in detecting long-term neurobehavioral effects of PDE. Split-half reliability for all CPT-dependent variables range between 0.73 and 0.95 among healthy children. Test-retest reliabilities for a 3-month interval range between 0.55 and 0.84.
Dependent variables related to SVA included (1) number of omission errors, (2) number of commission errors, and (3) reaction time to correct responses. Omission errors occurred when subjects failed to press the space-bar on trials containing non-“X” letters. Commission errors occurred when subjects pressed the spacebar on trials when the letter “X” was presented. Reaction time to correct responses was a subject’s mean response time to stimuli across all trials recorded in milliseconds. For CPT results to be valid, children must be somewhat motivated and understand task demands. If a child responded to less than 60% of the target letters (>3 SDs below the mean), his or her CPT protocol was deemed invalid.
Stanford-Binet Intelligence Scales: Fourth Edition
The Stanford-Binet Intelligence Scales—Fourth Edition (SB-IV) is a standardized test of intellectual functioning (M = 100, SD = 16) administered when children were 6 years of age to obtain an estimate of global intellectual functioning.38 The SB-IV has excellent validity and reliability. Internal consistency coefficients for composite scores range from 0.95 to 0.99.
Wide Range Achievement Test–3
The Wide Range Achievement Test–3 (WRAT-3) was administered to children at 7 years of age and reliably measures basic skills in reading, arithmetic, and spelling.39 Raw scores are converted into standard scores (M = 100, SD = 15).
Child Behavior Checklist
The Child Behavior Checklist (CBCL) was administered to caregivers when children were 7 years of age.40 It is a 120-item caregiver-report form that assesses child behavior problems and has very good reliability and validity. In this investigation, we focused on the attention problems subscale to determine associations between SVA performance and caregiver-reported attention problems in the home environment.
Birth Weight for Gestational Age
The child’s birth weight was recorded in the medical record at the University Hospital and standardized from the infant’s gestational age and gender using Center for Disease Center norms.41 Birth weight for gestational age was used as an indicator of intrauterine physical growth and has been associated with several cognitive outcomes in childhood.42
Nonmaternal Care
Changes in primary caregiver were recorded at each evaluation and defined as residing with a nonmaternal caregiver for at least one consecutive month. Number of caregiver changes prior to 7 years of age was calculated. A dichotomous variable was also generated to indicate whether the child was in maternal or nonmaternal care at the time of each visit. On the basis of whether the child was in continuous maternal care (i.e., PDE in maternal care) or nonmaternal care (i.e., PDE in nonmaternal care) at the 7-year assessment, two subgroups were created. The majority of nonmaternal care placements (95%) were with kin caregivers (e.g., aunt, grandmother). Children who had a history of foster care but lived with a birth parent at the time of the evaluation were excluded from analyses because they did not fit criteria for either continuous maternal care or nonmaternal care (n = 10).
Caregiver Measures
Caregiver demographic data collected at the 7-year visit included caregiver age, education, marital status, relationship to the child, employment, and public cash assistance status. Additionally, the following measures of the caregiver environment were assessed.
Center for Epidemiological Studies–Depression
The Center for Epidemiological Studies–Depression (CES-D) is a valid 20-item assessment of depressive symptomatology.43 This scale addresses multiple aspects of depression and requires respondents to rate their frequency of symptoms from 0 “rarely or never” to 3 “most or all the time,” with higher summed scores indicating higher levels of depression.
Current Drug Use
Caregivers completed the ASI35 and a drug use questionnaire to assess the frequency of current substance use. A dichotomous variable was generated reflecting self-reported cocaine and/or heroin use when children were 7 years old.
Kaufman Brief Intelligence Test
The Kaufman Brief Intelligence Test (K-BIT)44 was used to measure caregiver intellectual ability. The K-BIT generates a composite score with a mean of 100 and a standard deviation of 15, comprised of verbal and non-verbal abilities. The validity and reliability of the K-BIT have been established among urban, African-American populations.45
RESULTS
Preliminary Analyses
Based on our validity criteria for continous performance test (CPT) responses (response to >60% of targets), 19 children were excluded resulting in a final sample of 144. Those with invalid CPT responses did not differ by drug exposure classification, nonmaternal care status, or other demographic variables; however, those with invalid CPT scores [mean Stanford-Binet Intelligence Scales—Fourth Edition (SB-IV) composite = 77.5] had significantly lower intelligence quotitent (IQ) scores than those with valid CPT scores (mean SB-IV composite = 82.0), t (183) = −4.61, p < .05. Difficulty in understanding task instructions or following directions may have led to invalid response patterns.
An initial comparison of children from the community cohort CC group (n = 56), the prenatal drug exposure (PDE) maternal care group (n = 43), and PDE nonmaternal care group (n = 45) revealed that both PDE groups differed from the CC group on indicators of neonatal growth and prenatal tobacco exposure (see Table 1). Caregivers of children in the CC group and PDE groups did not differ in age at first pregnancy, prenatal alcohol exposure, educational attainment, intellectual functioning, marital status, public assistance status, or depressive symptomatology at the time of the 7-year visit. Caregivers in the both PDE groups were significantly older and less likely to be employed than caregivers in the CC group. Among PDE children, those currently in nonmaternal care had caregivers who were older and less likely to be using illicit drugs than children living continuously in maternal care. As such, birth weight for gestational age, prenatal tobacco exposure, caregiver age, employment status, and current drug use were selected as covariates in primary analyses based on bivariate associations, whereas child gender, home-intervention status, prenatal alcohol exposure, and child IQ were selected as covariates based on a priori theoretical considerations.
Table 1.
Sample Demographic Characteristics by Prenatal Drug Exposure and Caregiver Status
| Community Cohort (N = 56) | PDE in Maternal Care (N = 43) | PDE in Nonmaternal Care (N = 45) | ANOVA p | |
|---|---|---|---|---|
| Baseline Assessment | ||||
| Birth weight (g) | 3340 (592)a,b | 2803 (402)a | 2732 (397)b | <.001 |
| Weight for gestational age (z-score) | −.09 (1.0)a,b | −.86 (.7)a | −.92 (.8)b | <.001 |
| Head circumference (cm) | 34.4 (1.7)a,b | 32.8 (1.3)a | 32.7 (1.5)b | <.001 |
| Birth length (cm) | 50.4 (2.5)a,b | 48.1 (2.7)a | 47.8 (2.4)b | <.001 |
| Gender (% male) | 45% | 42% | 42% | .95 |
| Intervention status (%) | 0a,b | 58a | 58b | <.001 |
| Prenatal tobacco exposure (%) | 27a,b | 86a | 89b | <.001 |
| Prenatal alcohol exposure (%) | 30 | 37 | 38 | .68 |
| Prenatal marijuana exposure (%) | 0a,b | 37a | 22b | <.001 |
| Age 7 Assessment | ||||
| Caregiver age (at 7-yr assessment) | 30.8 (5.4)a,b | 36.8 (5.7)a,c | 46.3 (10.7)b,c | <.001 |
| Caregiver K-BIT standard score | 82.0 (11.0) | 82.8 (11.0) | 79.8 (14.0) | .48 |
| Caregiver education | 11.6 (1.3) | 11.5 (1.3) | 11.3 (1.9) | .58 |
| Caregiver married (%) | 20 | 7 | 18 | .19 |
| Caregiver current drug use (%) | 2%a | 44a,c | 4c | <.001 |
| Caregiver unemployment (%) | 9a,b | 28%a | 40%b | <.001 |
| Caregiver public assistance (%) | 48 | 54 | 60 | .50 |
| Caregiver depressive symptoms | 13.4 (10.8) | 11.7 (10.1) | 9.6 (8.0) | .15 |
Note: Post-hoc Tukey tests were run to determine significant between group differences on each outcome measure.
CC group differs significantly from the PDE maternal care group.
CC group differs significantly from the PDE non-maternal care group.
PDE maternal care group differs significantly from the PDE non-maternal care group.
CC, community cohort; PDE, prenatal drug exposure; ANOVA, analysis of variance.
Primary Analyses
To test the first two hypotheses that CPT performance differs by PDE history and caregiver group, we conducted two between-subjects univariate analyses of variance. First, we assessed whether PDE children performed more poorly than CC children on three CPT outcome variables (i.e., omission errors, commission errors, and reaction time), controlling for potentially confounding variables identified in preliminary analyses. Univariate analysis of covariance (ANCOVA) indicated that PDE children had significantly more omission errors than nonexposed children, F (1,134) = 4.37, p = .04, η2 = .03. Neither errors of commission nor mean reaction time were significantly associated with PDE history.
Caregiver group differences were examined (PDE in maternal care, PDE in nonmaternal care, and CC) on the same CPT outcome variables. ANCOVA revealed that errors of omission were significantly associated with PDE history and caregiver status, F (2,133) = 3.22, p = .04, η2 = .05, controlling for potential confounding variables (see Table 2). Post-hoc Tukey tests revealed that PDE children in maternal care had significantly more omission errors than children in the CC group. PDE children in nonmaternal care had an intermediate number of omission scores that did not differ significantly from PDE children in maternal care or CC children. Neither errors of commission nor mean reaction time were significantly associated with PDE history and caregiver status, after controlling for potential confounding variables.
Table 2.
Child Cognitive and Behavioral Functioning at Age 7 years by Prenatal Drug Exposure and Caregiver Status
| Sample Characteristics | Community Cohort (N = 56) | PDE in Maternal Care (N = 43) | PDE in Nonmaternal Care (N = 45) | ANCOVA p |
|---|---|---|---|---|
| Stanford-Binet composite (IQ) | 83.9 (11.1) | 83.0 (11.5) | 79.0 (8.4) | .21 |
| WRAT-3 reading achievement | 97.9 (16.3) | 94.1 (17.3) | 94.7 (13.0) | .60 |
| WRAT-3 spelling achievement | 98.0 (18.7) | 93.5 (15.9) | 96.1 (12.0) | .51 |
| WRAT-3 arithmetic achievement | 92.6 (16.8) | 89.2 (16.2) | 90.0 (16.4) | .26 |
| CBCL attention problems t score | 48.6 (9.4) | 49.0 (9.8) | 52.2 (11.3) | .11 |
| CPT total omission errors | 34.1 (25.0)a | 49.3 (32.9)a | 37.3 (24.2) | .04 |
| CPT total commission errors | 22.1 (7.0) | 21.8 (6.3) | 23.4 (6.2) | .20 |
| CPT mean reaction time (ms) | 529 (95) | 532 (82) | 521 (105) | .42 |
Note: Group comparisons using ANCOVA were adjusted for child gender, birth weight for gestational age, prenatal tobacco exposure, prenatal alcohol exposure, intervention status, child IQ (except when IQ was the outcome), caregiver age, employment status, and caregiver current drug use. Post-hoc Tukey tests were run to determine significant between group differences on each outcome measure.
CC group differs significantly from the PDE maternal care group. CC, community cohort; PDE, prenatal drug exposure; ANCOVA, analysis of covariance; WRAT-3, Wide Range Achievement Test–3; CBCL, Child Behavior Checklist; CPT, continuous performance test.
Finally, we tested the third hypothesis that sustained visual attention performance is associated with academic achievement and caregiver-reported attention problems. Associations between CPT performance and child intellectual, academic, and behavioral functioning at 7 years of age were assessed to establish convergent validity (see Table 3). Number of CPT omission errors was negatively associated with child IQ as well as reading, spelling, and math achievement, and positively associated with caregiver-reported attention problems. Number of CPT commission errors was negatively associated with child IQ, reading achievement, spelling achievement, and marginally negatively associated with math achievement. There were no significant associations between CPT reaction time and child IQ, academic achievement, or caregiver-reported attention problems (p’s > .05). Thus, CPT performance, particularly the number of omission and commission errors, was associated with ecologically valid measures of intellectual, academic, and behavioral functioning.
Table 3.
Intercorrelations Among Child Cognitive and Behavioral Functioning Variables at Age 7 years
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | |
|---|---|---|---|---|---|---|---|
| CPT total omission errors | — | ||||||
| CPT total commission errors | −.09 | — | |||||
| CPT mean reaction time (ms) | .42* | −.39* | — | ||||
| SB-IV IQ standard score | −.16** | −.28*** | −.05 | — | |||
| WRAT reading achievement | −.25*** | −.18† | −.08 | .54* | — | ||
| WRAT spelling achievement | −.26*** | −.22*** | .01 | .53* | .87* | — | |
| WRAT math achievement | −.22*** | −.14** | −.10 | .56* | .67* | .65* | — |
| CBCL Attention problem t-score | .19† | .08 | −.01 | −.28*** | −.30* | −.29*** | −.3* |
Note: Children assessed at age 7 except for SB-IV, which was administered at age of 6 years.
p < .001;
p < .10;
p < .01;
p < .05.
CPT, continuous performance test; SB-IV IQ, Stanford-Binet Intelligence Scales—Fourth Edition; WRAT, Wide Range Achievement Test; CBCL, Child Behavior Checklist.
DISCUSSION
We view the present findings from a biopsychosocial perspective that emphasizes the reciprocal influences of biological, psychological, and environmental factors on children’s neurocognitive development.21 We found that children with a history of prenatal drug exposure (PDE) demonstrate greater difficulties with sustained visual attention (SVA) than demographically matched comparison children, even after statistically controlling for other economic, social, and environmental risk factors. This overall difference between PDE and community coheret children indicates that exposure to cocaine and/or heroin in utero is associated with attentional problems that impair children’s ability to attend to visual stimuli over time.
PDE poses the most significant risk for SVA deficits in the context of continuous maternal care, particularly in the presence of persistent drug use. In the present study, PDE children placed in nonmaternal care were typically removed from environments characterized by persistent maternal drug-use and were compared with children who remained in such an environment. Nearly half of the caregivers in the PDE maternal care group self-reported recent cocaine or heroin use. As caregivers in all groups were equivalent on most demographic, socioeconomic, and intellectual variables, the depressive symptoms that characterize drug using mothers29,30 and other aspects of a drug-using lifestyle may have interfered with the provision of sensitive and stimulating child care, thereby contributing to children’s neurocognitive difficulties. Our results are consistent with evidence suggesting that children’s neurocognitive functioning is vulnerable to non-optimal care in the first few years of life.3,4
The present study extends findings of others who have reported that children with a history of PDE demonstrate difficulties on laboratory tasks of sustained attention.6,12–14,18,19 Studies that implemented the Conners’ continous performance test (CPT) found that PDE children demonstrated more omission errors than nonexposed children at school-age.5,12,19 However, these studies did not specifically examine children’s out-of-home placements because they related to CPT performance, but rather included a variable reflecting biological relatedness as a covariate in their analyses. Results from this study indicate that simply covarying out the effects of “nonmaternal care status” to reduce error variance does not sufficiently characterize a drug-exposed sample.
Drug-exposed infants and toddlers often display arousal modulation and selective attention problems.21,46–48 This initial vulnerability may present caregiving challenges that disrupt mother-child interactions, especially when occurring in the context of drug abuse. For example, previous findings from this cohort indicate that infants who remain in the care of drug-using mothers, even after the implementation of a developmentally oriented intervention, receive less responsive care and have worse cognitive outcomes than infants raised by non–drug-using mothers.34,49 The deficits displayed by children of drug-using mothers may result from factors associated with the mother’s drug-using lifestyle such as low levels of sensitivity, structure, and limited emotional availability.34,39 Low levels of responsive care throughout early childhood can interfere with the development of basic self-regulatory skills such as sustained attention.50 Overall, these findings reflect the importance of considering how children’s caregiving context after PDE can affect the organization and efficiency of attentional networks.21
Children’s performance on the Conners’ CPT task was associated with academic achievement and caregiver-reported attention problems. CPT errors of omission and commission were predictive of low achievement and parent-reported attention problems. Although CPTs are not sufficient to diagnose ADHD, they are among the most frequently used tasks for detecting deficits underlying ADHD such as poor sustained attention and impulsivity.51,52 Children with attention problems exhibit poor performance on these measures, marked by frequent omissions of target stimuli, a highly variable and impulsive response style, or an abnormal reaction time.53 Poor performance on these measures has been attributed to deficient regulatory functioning in the frontal lobes.52 The current study suggests that drug-exposed children, particularly those remaining in the care of mothers with persistent drug use, demonstrate less efficient SVA evidenced by increased omission errors and may be at increased risk for developmental problems. However, there remains unexplained variability in our models of children’s SVA, suggesting that additional moderators likely need to be addressed in future studies.
This study suggests that children raised in low-income, drug-using environments are at risk for SVA problems. Children in the care of substance-using mothers may benefit from early intervention services that facilitate cognitive development, particularly those that focus on parent-child interactions to enhance children’s developing self-regulatory skills.54 Our results suggest that children raised by parents with a history of persistent drug use are at risk for specific neurocognitive deficits and would benefit from targeted intervention services.
The current study has several limitations. The original sample was recruited to evaluate the effectiveness of an early developmental intervention. Data related to dosage of legal and illicit drugs were not available for the majority of subjects, limiting our ability to assess dose-related effects. Despite a lack of significant differences between children who remained enrolled in the study and children lost to follow-up, the high-attrition rate could have resulted in selection bias. We did not have adequate power to examine prenatal exposure effects pertaining to specific drugs, timing, or dosage, which can have important moderating effects.55 It is difficult to determine the unique effects of specific substances on neurocognitive outcomes, because most women who use drugs during pregnancy engage in polysubstance use.56 Caregiver’s drug use at follow-up was assessed via self-report. It is likely that drug use was underreported, particularly among the biological mothers who may have been under less scrutiny from child protective services than nonmaternal caregivers. This study would have benefited from biological assays of ongoing caregiver substance use. Additionally, the inclusion of behavioral observations of caregiver-child interactions may have been useful in examining the potential mediating role of caregiver responsiveness.
The present study has several methodological strengths including the use of routine screening and enrollment of drug-exposed children at birth who were matched with a demographically similar group of comparison children. The inclusion of numerous potentially confounding variables in statistical analyses reduced the likelihood that associations between PDE and SVA could be attributed to co-occurring risk factors associated with maternal drug use. The use of academic achievement and intelligence quotient (IQ) data as well as caregiver report of attentional functioning to examine the convergent validity of computerized testing strengthen present findings. An examination of caregiving context within the group of PDE children contributed to a better understanding of the factors contributing to children’s SVA.
In sum, PDE was associated with deficits in SVA in the context of continuous maternal care. Additionally, children in all groups displayed deficits in intellectual functioning and the ability to sustain concentration and focus on task goals over time relative to the entire population. Such findings confirm that poverty-related factors have an insidious effect on children’s neurocognitive development, regardless of drug exposure.8,57 SVA deficits were correlated with problems in academic functioning and caregiver-reported attention problems suggesting that child attentional performance in a controlled testing environment is meaningfully associated with functioning in home and school environments. Although specific learning problems were not evident at the age of 7 years, poor SVA and low IQ may place children at risk for subsequent academic, behavioral, and social problems as environmental demands increase. Early intervention services, therefore, should be accessible not only to children who have been removed from parental care, but to those who have not been identified by authorities. Interventions that focus on children’s self-regulation of mood, motivation, and arousal are critical in providing a foundation for later academic success.54
Acknowledgments
This study was supported by the National Institute of Drug Abuse (R01-DA07432 and R01-DA021059).
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