S1 Appendix -

Introduction

Alcohol intent (the susceptibility to initiating alcohol use) and alcohol sips (the initiation of alcohol) in youth are a multifactorial puzzle with many components. This research aims to examine the connection between genetic and environmental factors across sex, race and ethnicity.

Methods

Data was obtained from the twin hub of the Adolescent Brain Cognitive Development (ABCD) study at baseline (2016–2018). Variance component models were conducted to dissect the additive genetic (A), common (C) and unique environmental (E) effects on alcohol traits. The proportion of the total alcohol phenotypic variation attributable to additive genetic factors is reported as heritability (h²).

Results

The sample (n = 1,772) included an approximately equal male-female distribution. The 886 same-sex twin pairs were 60.4% dizygotic (DZ), 39.6% monozygotic (MZ), 65.4% non-Hispanic Whites, 13.9% non-Hispanic Blacks, 10.8% of Hispanics with a mean age of 121.2 months. Overall, genetic predisposition was moderate for alcohol intent (h² = 28%, p = .006) and low for alcohol initiation (h² = 4%, p = 0.83). Hispanics (h² = 53%, p < .0001) and Blacks (h² = 48%, p < .0001) demonstrated higher alcohol intent due to additive genetic factors than Whites (h² = 34%, p < .0001). Common environmental factors explained more variation in alcohol sips in females (c² = 63%, p = .001) than in males (c² = 55%, p = .003). Unique environmental factors largely attributed to alcohol intent, while common environmental factors explained the substantial variation in alcohol initiation.

Conclusion

Sex and racial/ethnic disparities in genetic and environmental risk factors for susceptibility to alcohol initiation can lead to significant health disparities. Certain populations may be at greater risk for alcohol use due to their genetic and ecological factors at an early age.