There is evidence suggesting that drinking alcohol during adolescence and early adulthood may have harmful effects on brain development. This is an important period in brain development, when the capacity to exert control over one's behavior, make decisions flexibly, anticipate and plan for the future, and behave in an adaptive manner develop more fully, all of which help lay the foundation for being a competent adult. It is important therefore to determine the exact nature of drinking effects on the brain. Because most people moderate their drinking, however, understanding the extent to which any effects of alcohol use lessen when individuals moderate their drinking or stop altogether is arguably equally important, with equally important public health implications.
These researchers are addressing these two broad aims in a sample of young adult twins from the Minnesota Center for Twin and Family Research (MCTFR) and in the UK Biobank sample. Twins represent a "natural experiment." The researchers will use a twin-differences design to determine whether differences between twins in their drinking patterns are associated with differences between them in brain structural and functional measures. In effect, the brain of the twin who drinks less or who reduces drinking more approximates what the brain of the twin who drinks more or who continues to drink heavily would have looked like had they not continued to drink heavily. This is the best approximation to a randomized experiment. The twin-difference design will inform the researchers about whether any associations they obtain between measures of drinking and patterns of drinking during adolescence and early adulthood and MRI measures of brain structure and function indicate that drinking, or reducing one's drinking, may actually cause the association, and which are part of a pre-existing liability for drinking heavily and continuing to drink heavily in the first place. Findings consistent with a causal influence of drinking patterns will be examined in the youngest participants in the UK Biobank sample. Replicating findings in an independent sample will increase the confidence that they are real.