Research Findings - Behavioral and Brain Development Research

Children's Cognitive Ability from 4 to 9 years old as a Function of Prenatal Cocaine Exposure, Gender, Environmental Risk, and Maternal Verbal Intelligence

This study investigated the effects of prenatal cocaine exposure on children's cognitive ability in a large sample of 231 children (91 cocaine exposed, 140 unexposed). The children were administered the Stanford-Binet IV Intelligence test at ages 4, 6, and 9 years. The sample consisted of 120 boys and 111 girls. Gender and age were used as potential moderators of the effects of cocaine exposure. An interaction was observed between gender and prenatal exposure; cocaine-exposed boys had lower composite IQ scores. This gender-specific effect on IQ remained after controlling for covariates such as prenatal exposure to other drugs, neonatal medical risk, environmental risk and maternal verbal intelligence. Age at assessment did not moderate this relationship in that the lower IQs for boys persisted across the age period. In boys exposed to cocaine, lower scores were seen in a number of domains which included the Abstract/Visual Reasoning subscale, as well as trends in lower scores for the Short-Term Memory and Verbal Reasoning subscales of the Stanford-Binet IV. Higher composite IQ scores were also predicted by a stimulating home environment and high maternal verbal IQ. It is unclear the reasons for the gender-specific effects; however, the results are consistent with prior research that show the central nervous system in male fetuses may be more susceptible to the influence of intrauterine factors. The findings of this study highlight the importance of examining gender as a potential moderator of prenatal exposure to cocaine. Bennett, D., Bendersky, M., and Lewis, M. Children's Cognitive Ability from 4 to 9 years old as a Function of Prenatal Cocaine Exposure, Environmental Risk, and Maternal Verbal Intelligence. Developmental Psychology, 44(4), pp. 919-928, 2008.

Body Size and Intelligence in 6-year-olds Exposed to Drugs of Abuse In Utero: Are Offspring of Teenage Mothers at Risk?

Prior research has indicated that the offspring born to adolescent mothers have lower birthweight and shorter gestational age. However, little is known about growth outcomes in older children and whether cognitive deficits in the offspring of adolescent mothers can be solely attributed to young maternal age. The purpose of this study was to examine differences in size and intelligence between two cohorts of offspring born to adolescent (n = 357) and adult (n = 668) mothers enrolled in prospective longitudinal studies of prenatal substance exposure and developmental outcomes. Both cohorts were of low socio-economic status and were assessed from gestation to 6 years of age. The teen cohort was evaluated in the mid-1990s and the adult cohorts were studied in the mid-1980s. After adjusting for covariates, including exposure to prenatal tobacco, alcohol, and marijuana, the results indicated that the offspring of adolescent mothers scored significantly lower on the Stanford-Binet composite score, as well as the quantitative, verbal reasoning and short-term memory scores. These children of adolescent mothers also had significantly smaller head circumference and higher weight to height ratio than the offspring of adult mothers. Further studies should follow these children to determine if additional problems are detected as the offspring of adolescent mothers mature and whether early interventions such as parenting support, nutritional information and enriched home environments may be beneficial to these children. Cornelius, M., Goldschmidt, L., Willford, J., Leech, S., Larkby, C., and Day, N. Body Size and Intelligence in 6-year-olds: Are Offspring of Teenage Mothers at Risk? Maternal and Child Health Journal, Aug 6, 2008; DOI 10.1007/s10995-008-0399-0 (Epub ahead of print).

Using Umbilical Cord Tissue to Detect Fetal Exposure to Illicit Drugs

The purpose of this study was to determine the utility of using an enzyme-linked immunosorbent assay (ELISA)-based screening test to analyze drugs in umbilical cord samples. The umbilical cord tissues were collected in a multicenter study in Utah and New Jersey when high-risk criteria were met for maternal illicit drug ingestion. The deidentified umbilical cord specimens were analyzed for five drug classes: methamphetamine, opiates, cocaine, cannabinoids and phencyclidine. A total of 498 umbilical cord samples were analyzed using the ELISA, as well a 'gold standard' test, consisting of gas or liquid chromatography tandem mass spectrometry. The mass spectrometric testing revealed that thirty two percent of the umbilical cord samples were positive for drugs. The sensitivity and specificity of the ELISA-based test for each class of drugs tested were as follows: methamphetamine 97 and 97%, opiates 90 and 98%, cocaine 90 and 100%, cannabinoids 96 and 98% and phencyclidine (only 1 of the 498 umbilical cord sample was positive for phencyclidine) 100 and 100%. These results reveal that the ELISA-based tests on umbilical cord tissue are sufficient to detect fetal exposure to illicit drugs and because of the rapid send-off time, may be more suitable than meconium or hair-based methods. Montgomery, D., Plate, C., Jones, M., Jones, J., Rios, R., Lambert, D., Schumtz, N., Wiedmeier, S., Burnett, J., Ail, S., Brandel, D., Maichuck, G., Durham, C., Henry, E., and Christensen, R. Using Umbilical Cord Tissue to Detect Fetal Exposure to Illicit Drugs: A Multicenter Study in Utah and New Jersey. Journal of Perinatology, 28(11), pp. 750-753, 2008.

Pregnancy Smoking in Context: The Influence of Multiple Levels of Stress

Although smoking has steadily declined during the past 15 years, approximately 10.2% of pregnant women smoke cigarettes during pregnancy. Smoking during pregnancy is associated with numerous adverse perinatal outcomes including low birth weight, premature delivery, infant mortality and long-term behavioral sequelae. The current study utilized data from the Family Health and Development Project which is a longitudinal study that examines the effects of maternal smoking during pregnancy on infant behavioral vulnerability. The purpose of the current project was to examine predictors of persistent smoking and smoking intensity during the third trimester in a sample of 113 pregnant women with a mean age of 29.7 years. Using a single comprehensive structural equation model, latent variables comprised of indicators of stress and resources were derived for three contextual levels: intimate social context, broader social context and socioeconomic context. The results revealed that the probability of being a persistent pregnancy smoker was positively associated with a stressful socioeconomic context (probit regression coefficient = .70, p< .05). Smoking rate was predicted by the broader social context with greater stress and fewer resources associated with a greater number of cigarettes smoked during the third trimester (standardized regression coefficient = .81, p< .05). Results suggest that pregnancy smoking may be influenced by psychosocial context at multiple levels. Elucidating the differences between pregnancy smokers and nonsmokers or quitters may inform smoking cessation and reduction interventions with this population. Weaver, K., Campbell, R., Mermelstein, R., and Wakschlag, L. Pregnancy Smoking in Context: The Influence of Multiple Levels of Stress. Nicotine & Tobacco Research, 10(6), pp. 1065-1073, 2008.

Neurodevelopmental Changes in Verbal Working Memory Load-Dependency: An fMRI Investigation

Prior behavioral research has indicated that the development of working memory (transient storage and manipulation of information) follows a protracted course of maturation reaching adult-like levels around middle adolescence. Structural changes in frontal-parietal association cortices are important for performance on working memory (WM) aptitude. Also in support of the postulated phonological loop of verbal working memory is the cerebellum whose function along with the frontal and parietal cortices, has been shown to exhibit linear WM load-dependent activation in adults. It remains unclear; however, whether WM load-dependent relationships exist for cerebro-cerebellar networks in developmental populations. The purpose of the present study was to investigate developmental changes in WM load-dependent cerebro-cerebellar activation using fMRI and a verbal Sternberg WM task. The sample consisted of 30 typically developing children, adolescents, and young adults between the ages of 7 and 28. The results demonstrated that the extent to which cerebro-cerebellar verbal working memory networks are activated in response to increasing task difficulty changes significantly between childhood and adolescence. In both adolescents and adults, increasing WM load was associated with increasing activation in frontal, parietal and cerebellar regions. In contrast, only the left ventral prefrontal cortex was recruited in response to increasing WM load in children. O'Hare, E., Lu, L., Houston, S., Bookheimer, S. and Sowell, E. Neurodevelopmental Changes in Verbal Working Memory Load-Dependency: An fMRI Investigation. Neuroimage, 42(4), pp. 1678-1685, 2008.

Environmental Stimulation, Parental Nurturance and Cognitive Development in Humans

Although animal models exist that examine the effects of environmental stimulation and parental nurturance on brain development, little is known about the relations between cognitive development and childhood experience in humans. The current project utilized a sample that consisted of 110 African American middle school-aged children (mean age 11.7 years) to identify the human counterparts of early life experience studied in animals, environmental enrichment and stress-buffering maternal behaviors. These children had been recruited at birth for a longitudinal study that examined the effects of gestational cocaine exposure utilizing ecologically valid in-home measures of childhood experience and measures of cognitive ability assessed later in the laboratory. The subjects were born of mothers receiving public assistance and were at or near term. None of the children had Fetal Alcohol Syndrome or any chromosomal disorder known to be associated with developmental delay. The analyses conducted indicated that there was a relationship between parental nurturance and memory development which is in agreement with the animal literature on maternal buffering of stress hormone effects on hippocampal development. However, language development was shown to selectively relate to environmental stimulation and not to parental nurturance. Although it is uncertain whether the results obtained with this sample would generalize to children of a different ethnicity or socioeconomic background, the findings provide a strong scientific incentive to better understand the complex relations among socioeconomic class, life experience and cognitive development. Farah, M., Betancourt L., Shera, D., Savage J., Giannetta J., Brodsky N., Malmud, E., and Hurt H. Environmental Stimulation, Parental Nurturance and Cognitive Development in Humans. Developmental Science, 11(5), pp. 793-801, 2008.

Neighborhood Disorganization, Substance Use, and Violence Among Adolescents in Puerto Rico

The current project utilized data from a larger longitudinal project which was designed to examine risk and resilience to HIV/AIDS in adolescents' ages 12 to 15 years in San Juan, Puerto Rico. The purpose of the current study was to determine how neighborhoods influence adolescent violence in poor communities. Using a cross-sectional design, the incidence of violent behaviors among participants was obtained via a self-completed questionnaire, as well as an interviewer questionnaire. Demographics, characteristics and neighborhood social disorganization using the concepts of both physical disorders (i.e. environmental deterioration of urban landscapes) and social disorders (threatening behaviors by individuals in social spaces) were utilized. The results indicated that social disorder in the neighborhood was positively associated with adolescent violence. The display of adult violence may lead adolescents to view violence as an accepted behavior. It is also possible that social support and resources are limited in socially disorganized neighborhoods which might lead to the failure to organize on their own behalf. Reyes, J., Robles, R., Colon, H., Negron, J., Matos, T., Calderon, J., and Perez, O. Neighborhood Disorganization, Substance Use, and Violence Among Adolescents in Puerto Rico. Journal of Interpersonal Violence, 23(11), pp. 1499-1512, November, 2008.

Towards an Explanation of Subjective Ketamine Experiences among Young Injection Drug Users

This study explored factors that shape or influence the reported subjective experiences of the drug ketamine which has powerful sedative and hallucinogenic properties. The data were collected as part of a study examining health risks associated with injecting ketamine. Two hundred and thirteen injection drug users between the ages of 16 and 29 years of age who had injected ketamine at least once within the past two years were recruited from New York, Los Angeles and New Orleans between 2004 and 2006. In depth interviews were conducted that focused on specific ketamine events such as first injection of ketamine, most recent injection of ketamine and most recent experience sniffing ketamine. The results of these interviews revealed that both positive and negative subjective experiences during any given ketamine event were shaped by two or more of the following six factors: polydrug use, drug using history, mode of administration, quantity and quality of ketamine, user group, and setting. Subjective ketamine experiences were also influenced by a lifestyle characterized by homelessness and traveling. Although these findings may not generalize to all ketamine users, the model used in this study may inform future studies seeking to examine the subjective experiences on ketamine or other drug use. Lankenau, S., Sanders, B., Bloom, J., and Hathazi, D. Towards an Explanation of Subjective Ketamine Experiences among Young Injection Drug Users. Addiction Research and Theory, 16(3), pp. 273-287, 2008.

The Effects of Low Literacy and Cognitive Impairment on Medication Adherence in HIV-Positive Injecting Drug Users

This study utilized two factors (low literacy and cognitive impairment) in combination to examine the effects on non-adherence to medications for HIV/AIDS. The sample included 57 HIV-positive injecting drug users who were community-recruited. Performance on a reading test and a brief neuropsychological battery classified the participants into one of four groups: high literacy/high cognition, low literacy/high cognition, high literacy/low cognition and low literacy/low cognition. The results obtained from chi-square and bivariate analyses characterized the literacy and cognitive skills of the overall sample. After controlling for recent cocaine use, the relationship of the four groups to non-adherence (<95%) was tested using a logistic regression analysis. Severe deficits were noted in psychomotor functioning and performance on measures of literacy and cognitive functioning were below average. Those individuals who were classified as low literate/low cognition were nine times more likely to be non-adherent than the referent high literate/high cognition group. The findings from this study suggest that interventions designed to improve cognitive deficits in drug users diagnosed with HIV would help to improve adherence to HIV medications. Waldrop-Valverde, D., Jones, D., Weiss, S., Kumar, M., and Metsch, L. The Effects of Low Literacy and Cognitive Impairment on Medication Adherence in HIV-Positive Injecting Drug Users. AIDS Care, 20(10), pp. 1202-1210, 2008.