"Among 12th graders, the highest noncontinuation rate is observed for inhalants (64%), followed by crystal methamphetamine (ice) (50%) and narcotics other than heroin (49%). Many inhalants are used primarily at a younger age, and use is often not continued into 12th grade. The rank ordering for noncontinuation of other drugs is as follows: tranquilizers, cigarettes, methamphetamine, cocaine other than crack, amphetamines, cocaine, sedatives (barbiturates), heroin, MDMA (ecstasy, Molly), hallucinogens, and steroids (all between 34% and 45%).

"• The drugs most likely to be continued include alcohol use to the point of being drunk (only a 20% noncontinuation rate), marijuana (18%), nicotine vaping (13%), marijuana vaping (12%), and any alcohol use (11%). It is important to recognize that substantial proportions of students who try the various illicit drugs do not continue use, even into later adolescence. (Note: Use of heroin with and without a needle is not included due to very low case counts.

"• The noncontinuation rate of 12% for marijuana vaping is the second lowest of all substances assessed, with alcohol lower (at 11%). This low level of noncontinuation stems in part from the record high levels of past 12-month incidence in 2019, which was the second highest increase ever recorded by MTF in its history. Any past-year use lowers noncontinuation, by definition, and all incidence is past-year use. Should the level of incidence recede in the coming years, then noncontinuation will subsequently increase. Nevertheless, the noncontinuation rate of marijuana vaping will likely continue to rank as one of the lowest, even with future increases, as long as 12th graders perceive vaping as a form of drug use with relatively little risk of physical harm (discussed in Chapter 8).

"• The noncontinuation rate of 13% for nicotine vaping is the third lowest of all substances assessed (only marijuana vaping and alcohol are lower at 12% and 11%, respectively). Part of the reason for its low level of noncontinuation in 2019 is its very high level of incidence, which by definition lowers noncontinuation (discussed in more detail immediately above for marijuana vaping). Also likely contributing to the low noncontinuation level is the very low level of perceived risk for nicotine vaping (discussed in Chapter 8). Nevertheless, even with a rate higher than its current level we expect in future years that nicotine vaping will continue to have one of the lowest of all noncontinuation rates, given that nicotine is a highly addictive substance.

"• It is noteworthy that, of all the 12th graders who have ever used crack (1.7%), only about one third (0.7%) report current use and 0.2% of the total sample report current daily use. While there is no question that crack is highly addictive, evidence from MTF has suggested consistently that it is not addictive on the first use, contrary to what was often alleged in the past.

"• In contrast to illicit drugs, noncontinuation rates for licit drugs are extremely low. Among 12th grade students alcohol has a lifetime prevalence of 59% and an annual prevalence of 52%, yielding a noncontinuation rate of only 11% (52%/59%).

"• Noncontinuation had to be defined differently for cigarettes because respondents are not asked to report on their cigarette use in the past year. The noncontinuation rate is thus defined as the percentage of those who say they had ever smoked who also reported not smoking at all during the past 30 days rather than the past year. Of the 12th graders who said they were ever regular smokers, 74% have ceased active use.

"• Noncontinuation is defined for smokeless tobacco much the same way as for cigarettes. In 2019, 65% of lifetime regular users did not use in the past 30 days.

"• In addition to providing 12th grade data, Figure 4-3 presents comparable data on noncontinuation rates based on responses of 8th and 10th graders. As mentioned above, the drugs have been left in the same order as the rank-ordered drugs in 12th grade to facilitate comparison across grades.

"• The noncontinuation rates for inhalants are very high and rise with grade level (51%, 59%, and 64% in grades 8, 10, and 12)."