The present study used a monozygotic (MZ) cotwin-control (CTC) design to investigate associations between alcohol use and performance on the Iowa gambling task (IGT) in a sample of 96 adolescents (half female). The MZ CTC design is well suited to shed light on whether poor decision-making, as reflected on IGT performance, predisposes individuals to abuse substances or is a consequence of use. Participants completed structural MRI scans as well, from which we derived gray matter volumes for cortical and subcortical regions involved in IGT performance and reduced in adolescents with problematic alcohol use. Drinking was associated with poorer task performance and with reduced volume of the left lateral orbital-frontal cortex. CTC analyses indicated that the former was due to differences between members of twin pairs in alcohol use (suggesting a causal effect of alcohol), whereas the latter was due to factors shared by twins (consistent with a pre-existing vulnerability for use). Although these preliminary findings warrant replication, they suggest that normative levels of alcohol use may diminish the quality of adolescent decision-making and thus have potentially important public health implications.
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Acknowledgments The authors thank Chrissy Evenson for her conscientiousness, dedication, and great skill in coordinating AdBrain and Lyric Jorgenson for graciously assisting with MRI scans. This research was supported by National Institutes of Health grants R21 AA 017314, R37 DA 05147, and R01 DA036216, as well as P30 NS057091 and P30 NS076408 for ‘‘Institutional Center Cores for Advanced Neuroimaging’’ at the Center for Magnetic Resonance Research.
- Identical twins