Examining the link between age of alcohol initiation, adolescent alcohol use and adult substance use

Abstract Background Understanding the relationship between adolescent alcohol use and adult substance use is important for prevention programmes. Existing evidence presents divergent findings and potential mechanisms are debated. Methods We estimated associations between the age of alcohol initiation and alcohol use at age 17 and substance use at age 20 in a nationally representative cohort (n = 4554). Weighted logistic regression models were fitted using Generalised Estimating Equations in multiply imputed and complete case data. Results Our analysis identified that 27% of participants reported first alcohol use at ≤ 14 years old, with 37% engaging in risky alcohol use by age 17. At age 20, 14% reported hazardous alcohol use, while 38% used tobacco, 24% cannabis, and 28% other drugs. The age at which alcohol was initiated and risky alcohol use at 17 years old were both strongly associated with alcohol, tobacco, cannabis and other illicit drug use at 20 years old. Sequential change in effect estimates coupled with non-overlapping confidence intervals suggest a dose-response relationship between age of alcohol initiation and tobacco and other drug use at age 20. Conclusions First use of alcohol at 14 or younger was common. Earlier alcohol initiation and risky alcohol use are each associated with substantially elevated risk for substance use at 20 years old even after accounting for common liability factors. Acknowledgement: Growing Up in Ireland (GUI) is funded by the Department of Children, Equality, Disability, Integration and Youth (DCEDIY). It is managed by DCEDIY in association with the Central Statistics Office (CSO). Results in this report are based on analyses of data from Research Microdata Files provided by the CSO. Neither the CSO nor DCEDIY take any responsibility for the views expressed or the outputs generated from these analyses. Key messages • Delaying alcohol initiation and preventing risky alcohol use during adolescence may reduce levels of substance use in young adults. • Self-reported early use of alcohol remains common.