Fig. 1.

Early initiation of substance use increases the risk of substance abuse or dependence. Substance abuse or dependence among persons aged 18 or older (black bars) is plotted by age at first substance use for A) nicotine, B) alcohol, and C) illicit drugs (marijuana, cocaine/crack, heroin, hallucinogens, inhalants, non-medial prescription use, and methamphetamine), based on results of the 2014 National Survey on Substance use and Health (SAMHSA, 2015a, SAMHSA, 2015b). Past year initiation of each drug (gray bars) is also shown for each age group for comparison; this data is based on the 2013 National Survey on Substance use and Health (SAMHSA, 2014). Although adolescents aged 15–17 are most likely to experiment with drugs of abuse, initiation before age 14 is associated with the highest risk of developing abuse or dependence later in life.