Alcohol use and cognitive functioning in young adults: improving causal inference

There have been few longitudinal studies of association between alcohol use and cognitive functioning in young people. A group of researchers from Bristol University investigated whether alcohol use is a causal risk factor for deficient cognitive functioning in young adults.
The observational study included 3,155 adolescents and their parents from the Avon Longitudinal Study of Parents and Children (ALSPAC). Genetic instruments for alcohol use were based on almost 1,000,000 individuals from the GWAS & Sequencing Consortium of Alcohol and Nicotine use (GSCAN). Genome-wide association studies for cognitive outcomes were based on 2,500 individuals from ALSPAC.
Binge drinking was assessed at approximately 16, 17, 18, 21, and 23 years. Cognitive functioning comprised working memory, response inhibition, and emotion recognition assessed at 24 years of age. Ninety-nine independent genome-wide significant single nucleotide polymorphisms (SNPs) associated with ‘number of drinks per week’ were used as the genetic instrument for alcohol consumption. Potential confounders were included in the observational analyses.
Four binge drinking classes were identified: ‘low-risk’ (41%), ‘early-onset monthly’ (19%), ‘adult frequent’ (23%), and ‘early-onset frequent’ (17%). The association between early-onset frequent binge drinking and cognitive functioning: working memory, response inhibition and emotion recognition in comparison to low-risk drinkers was inconclusive as to whether a difference was present. Two-sample MR analyses similarly provided little evidence that alcohol use is associated with deficits in working memory using the inverse variance weight, response inhibition and emotion recognition.
The researchers conclude that binge drinking in adolescence and early adulthood may not be causally related to deficiencies in working memory, response inhibition, or emotion recognition in youths.
Source: Mahedy L, Suddell S, Skirrow C, et al. Alcohol use and cognitive functioning in young adults: improving causal inference [published online ahead of print, 2020 Apr 25]. Addiction. 2020;10.1111/add.15100.