Early marijuana or alcohol use is related to later substance use disorders, according to data from the National Survey on Drug Use and Health (NSDUH). Adults who first used marijuana at age 14 or younger were more than twice as likely to meet the criteria for past year illicit drug abuse or dependence than those who first used marijuana between the ages of 15 and 17 (12.8% vs. 5.6%) and nearly five times more likely than those who started when they were 18 or older (12.8% vs. 2.6%). Similar results were found for early alcohol use; those who first used alcohol at or before the age of 14 were nearly twice as likely to meet the criteria for past year alcohol abuse or dependence than those who started
using alcohol between the ages of 15 and 17 (16.2% vs. 9.7%) and more than four times more likely than those who started using alcohol at the age of 18 or older (16.2% vs. 3.8%). While these findings illustrate the need for early alcohol and drug prevention efforts, it is likely that early substance use is an indicator of a disposition to engage in a variety of high-risk behaviors, suggesting that prevention efforts that encompass the whole person may be more effective.