aUse of "any illicit drug" includes any use of marijuana, LSD, other hallucinogens, crack, other cocaine, or heroin, or any use of other narcotics, amphetamines, barbiturates, methaqualone (excluded since 1990), or tranquilizers not under a doctor's orders.
bBeginning in 1982 the question about amphetamine use was revised to get respondents to exclude the inappropriate reporting of nonprescription amphetamins. The prevalence of use rate dropped slightly as a result of this methodological change.
cData based on four of five forms in 1976-88; N is four-fifths of N indicated. Data based on five of six forms in 1989-98; N is five-sixths of N indicated. Data based on three of six forms beginning in 1999; N is one-half of N indicated.
dAdjusted for underreporting of amyl and butyl nitrites. See text for details.
eData based on one form; N is one-fifth of N indicated in 1979-88 and one-sixth of N indicated in 1989-99.
fQuestion text changed slightly in 1987.
gAdjusted for underreporting of PCP. See text for details.
hData based on one of five forms in 1986; N is one-fifth of N indicated. Data based on two forms in 1987-89; N is two-fifths of N indicated in 1987-88 and two-sixths of N indicated in 1989. Data based on six forms in 1990-99.
iData based on one form in 1987-89; N is one-fifth of N indicated in 1987-88 and one-sixth of N indicated in 1989. Data based on four of six forms in 1990-99; N is four-sixths of N indicated.
jIn 1995 the heroin question was changed in half of the questionnaire forms. Separate questions were asked for use with injection and without injection. Data presented here represent the combined data from all forms.
kOnly drug use which was not under a doctor's orders is included here.
lData based on two of six forms; N is two-sixths of N indicated. Steroid data based on one of six forms in 1989-90; N is one-sixth of N indicated in 1989-90. Steroid data based on two of six forms since 1991; N is two-sixths of N indicated since 1991.
mSedatives: Data based on five forms in 1975-88, six forms in 1989, one form in 1990 (N is one-sixth of N indicated in 1990), and six forms of data adjusted by one-form data beginning in 1991. Methaqualone: Data based on five forms in 1975-88, six forms in 1989, and one of six forms beginning in 1990 (N is one-sixth of N indicated beginning in 1990).
nData based on five forms in 1975-88 and on six forms in 1989-92. In 1993, the question text was changed slightly in three of six forms to indicate that a "drink" meant "more than a few sips." The data in the upper line for alcohol came from the three forms using the original wording (N is three-sixths of N indicated), while the data in the lower line came from the three forms containing the revised wording (N is three-sixths of N indicated). Data for 1994-99 were based on all six forms.
oThe prevalence of use of smokeless tobacco was not asked of twelfth graders in 1990 and 1991. Prior to 1990 the prevalence of use question on smokeless tobacco was located near the end of one twelfth-grade questionnaire form, whereas after 1991 the question was placed earlier and in a different form. This shift could explain the discontinuities between the corresponding data.
SOURCE: The Monitoring the Future Study, the University of Michigan.