This report is guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.13 The following selection criteria were applied: Studies which defined AFD as the age at which a participant had a first drink of more than a few sips of alcohol were included, while studies which assessed only age of first intoxication or the initiation of regular drinking were excluded, because these will widely occur at a later age. Only cohort studies comprising general population samples were included, with a requirement for at least 3 years follow-up between initial measurement of AFD in adolescence and the assessment of alcohol related outcomes. This interval, somewhat arbitrarily allows for the development of problems after initiation. Included studies were also required to measure alcohol related outcomes in adulthood, defined here as 18 years or over. Studies of special populations such as children of alcoholics were excluded. Relevant alcohol related outcomes were defined as: measures of consumption, including measures of the frequency and quantity of alcohol use; Diagnostic and Statistical Manual of Mental Disorders or International Classification of Diseases defined
