Substance use initiation is also known as incidence or first time use. National Survey on Drug Use and Health (NSDUH) provides a variety of estimates related to initiation of substance use among the youths aged 12 to 17 and young adults aged 18 to 25. Individuals who initiated use within the past 12 months are referred to as recent or past year initiates. This survey also includes illicit drug, cigarette, and alcohol use. Following are the results of the survey regarding the substance initiation.

In 2009, an estimated 3.1 million persons aged 12 or older used an illicit drug for the first time within the past 12 months. On an average 8,500 initiated the use of illicit drugs per day in 2009. About 56.8 initiates were younger than age 18 when they first used, and 51.8 percent of new users were female. Majority of the illicit drug initiates in 2009 said that their first drug was marijuana, nearly 28.6 percent initiated with psycho therapeutics and 9.8 percent initiated inhalants.

Psycho therapeutics include the non medical use of any prescription type pain relievers, tranquilizers, stimulants, or sedatives. In 2009, there were 2.6 million persons aged 12 or older who used psycho therapeutics non medically for the first time within the past year which averages out to around 7,000 initiates per day.

In 2009, there were 4.6 million persons aged 12 or older who had used alcohol for the first time within the past 12 months and this averages to 12,500 initiates per day. Number of persons who initiated smoking in 2009 was 2.5 million which was similar to the rates in 2008. The 2009 estimate averages out to approximately 6,900 new cigarette smokers every day. 58.8 percent of the new cigarette smokers in 2009 were under age 18 when they first smoked cigarettes.