Health and Developmental Consequences of Youth Drug Abuse

Research Findings from September, 2004 Director's Report

This section lists selected summaries from NIDA funded research projects that investigate the developmental implications of drug use. The summaries provided were selected from recent issues of the Director's Report to the National Advisory Council on Drug Abuse. For a more comprehensive listing of NIDA funded projects see the Director's Report.

Impact of Cannabis Use on Brain Function in Adolescents

Dr. Leslie Jacobsen and colleagues reported on a pilot study to determine the potential effect of cannabis exposure in adolescents. Seven adolescent marijuana users that also used tobacco, seven tobacco users with a minimal history of cannabis use, and seven non-smokers with no history of cannabis use were compared. Participants were tested on a number of assessments of attention and working memory while fMRI was used to assess hippocampal activation patterns, since both preclinical and clinical evidence suggests that cannabis modulates hippocampal function. Cannabis users were found to have significantly more errors on a continuous performance task, which tests sustained attention, than participants that did not use tobacco and had not used cannabis. Cannabis users also had more errors than tobacco users, although the difference did not reach statistical significance. The performance of cannabis users on the most difficult working memory task used (the 2-back task) was found to differ significantly from both the tobacco-using group and those individuals that used neither tobacco nor cannabis. Analysis across all tasks showed that, overall, cannabis users performed worse than the individuals in the other two groups and also differed in their hippocampal activation pattern from non-using adolescents. Although a pilot study with relatively few participants, the data from this investigation do suggest that adolescent use of cannabis may affect memory and attention and that these effects are reflected in neurobiological alterations. Jacobsen, L.K., Mencl, E.W., Westerveld, M. and Pugh, K.R., Annals of the New York Academy of Sciences. 1021, pp. 384-390, 2004.

Developmental Trajectories of Cocaine-and-other-drug Exposed and Non-cocaine-exposed Children

Dr. Linda Mayes and colleagues at Yale University report data on the effects of prenatal cocaine exposure on the developmental trajectory of mental and motor performance, as measured by the Bayley Scales of Infant Development-II, in children assessed bi-yearly from age 3 months to age 36 months. Three groups of children in an ongoing longitudinal study were studied: those prenatally exposed to cocaine and other drugs (n= 265), those exposed to other drugs including alcohol, tobacco, and/or marijuana but not cocaine (n= 66), and those not exposed to any drugs prenatally (n= 129). All three groups are a very high-risk sample characterized by extreme poverty, adversity, and environmental instability. Dr. Mayes and her colleagues found that the Bayley motor index indicated a decline in motor performance across time in all three groups. The decline was greater in the cocaine-exposed group, though not statistically significant. The Bayley mental index also indicated a decline across age, but only to 24 months. Although the rate of mental performance decline, i.e., the trajectory, did not differ among the groups, the cocaine-exposed children had lower mental performance scores than those in the other two groups at each age level. These data indicate that impoverished cocaine- and non-cocaine-exposed children develop along the same trajectories in the mental and motor domains, but that cocaine-exposed children exhibit delays in mental development relative to the non-cocaine-exposed children. Mayes, L.C., Cicchetti, D., Acharyya, S. and Zhang, H. Developmental Trajectories of Cocaine-and-other-drug exposed and Non-cocaine-exposed Children. Journal of Developmental and Behavioral Pediatrics, 24, pp. 1-13, 2003.

Cerebral Reserve Capacity: Implications for Alcohol and Drug Abuse

This review article discusses cerebral reserve capacity (or functional reserve), which refers to the brain's ability to maintain function when confronted by degenerative processes. There is accumulating evidence that the magnitude of reserve capacity is important in determining the onset and progression of the clinical manifestations of neurodegenerative brain diseases. The concept of cerebral functional reserve has important implications for alcohol and drug abuse morbidity. First, given the high genetic contribution to substance abuse, there is an increased likelihood that the parents of substance abusers were substance abusers themselves. Substance abuse during pregnancy can inhibit brain growth, resulting in reduced brain size and reduced reserve capacity (and therefore less ability to compensate for loss of function later in life). Second, substance abuse is often coupled with poverty, and both substance abuse and poverty are associated with some of the same conditions that reduce brain growth. The authors comment on the most important public health implications of the cerebral reserve capacity model for drug and alcohol addiction. Fein, G. and Di Sclafani, V. Alcohol, 32(1), pp. 63-67, 2004.

Children's Intuitive Theories of Drug Action

In an effort to develop a method for characterizing children's intuitive theories of drug action, 217 children (53.7% girls) in grades 1 through 6 were interviewed about how alcohol and cocaine cause behavioral changes in users. Using Piagetian and intuitive theories perspectives children's responses to interview questions were classified in terms of both structure and content. With respect to structure, responses were coded for their complexity of causal reasoning, coherence, and level of construction of a casual explanatory framework with nodes, links, and causal mechanisms. In terms of content, responses were coded for relevant biological ontology, mastery of propositions in a scientifically correct theory of drug action, and reliance on alternative theoretical models. Scores on all measures of structure and content increased with age, especially between first and second grade and third and fourth grade. Growth between third/fourth and fifth/sixth grades was more evident for cocaine than for alcohol. Overall, elementary school age children appear capable of framing causal explanations of drug action and they possess relevant biological knowledge, particularly about the central role of the brain in mediating the effects of drugs on behavior. Davies, E.P., Sigelman, C.K., Bridges, L.J., Rinehart, C.S. and Sorongon, A.G. A Characterization of Children's Intuitive Theories of Drug Action. Applied Developmental Science, 8, pp. 58-74, 2004.

Chronic Marijuana Use Associated With Dropping Out of School

This paper explores the relationship between adolescent marijuana use and school attendance. Data were pooled from the 1997 and 1998 National Household Surveys on Drug Abuse to form a sample of 15,168 adolescents, aged 12Ñ18 years, who had not yet complete high school. The analysis determined the role of marijuana use in adolescent school dropout and, conditional on being enrolled, estimated the number of days truant. The potential endogeneity of marijuana use was tested in all specifications. The results indicate that any marijuana use was positively associated with school dropout and truancy in all models. However, when chronic marijuana use (weekly or more frequent) was distinguished from non-chronic marijuana use (less frequent than weekly), chronic marijuana use was found to be the dominant factor in these relationships. The results have important implications for educators, substance abuse treatment providers, and policymakers. Roebuck, M.C., French, M.T. and Dennis, M.L. Chronic Marijuana Use Associated With Dropping Out of School. Economics of Education Review, 23, pp. 133Ñ141, 2004.