mental health services,
substance abuse treatment,
Date of Collection:
Unit of Observation:
The civilian, noninstitutionalized population of the
United States aged 12 and older, including residents of
noninstitutional group quarters such as college dormitories, group
homes, shelters, rooming houses, and civilians dwelling on military
Data Collection Notes:
Data were collected and prepared for release by
Research Triangle Institute, Research Triangle Park, NC.
National Household Survey on Drug Abuse questionnaire and estimation
methodology changed with the implementation of the 1994-B
survey. Therefore, estimates produced from the 1998 survey are not
comparable to those produced from the 1994-A and earlier surveys.
This version of the 1998 NHSDA public release file does not contain
data collected on the Parenting Experiences answer sheet (#21) or the
questionnaire roster (QD-47) contained in the "Non-Core"
Demographics section, nor does this file include various recoded
variables that are typically created from the roster data and have
been included in past public release files. All the necessary
processing of these data and weight calculations for use of these data
had not been completed by the data producers at the time of the data
deposit. The data producers anticipate release at a later
date of an updated version of the 1998 NHSDA public use file,
containing additional questionnaire data, variables derived using
these data, and additional weights.
For selected variables,
statistical imputation was performed following logical imputation to
replace missing responses. These variables are identified in the
codebook as "...LOGICALLY IMPUTED" and "...imputed" for the
logical procedure or by the designation "IMPUTATION-REVISED" in the
variable label when the statistical procedure was also performed. The
names of statistically imputed variables begin with the letters
"IR". For each imputation-revised variable there is a corresponding
imputation indicator variable that indicates whether a case's value on
the variable resulted from an interview response or was imputed by the
hot-deck technique. Hot-deck imputation is described in the
The "basic sampling weights" are equal to the inverse
of the probabilities of selection of sample respondents. To obtain
"final NHSDA weights," the basic weights were adjusted to take into
account dwelling unit-level and individual-level nonresponse and then
further adjusted to ensure consistency with intercensal population
projections from the United States Bureau of the Census.
protect the privacy of respondents, all variables that could be used
to identify individuals have been encrypted or collapsed in the public
use file. These modifications should not affect analytic uses of the
public use file.
Users who wish to replicate results published in
the NHSDA Main Findings Report or other SAMHSA reports should use the
1998 NHSDA imputed data for prevalence estimates rather than raw data
from the questionnaire or drug answer sheets.
For some drugs that have multiple names, questions regarding the use of that drug may be asked for each distinct name. For example, even though methamphetamine, methedrine and desoxyn are the same drug, their use was measured in three separate variables.
Multistage area probability sample design involving five
selection stages: (1) primary sampling unit (PSU) areas (e.g.,
counties), (2) subareas within primary areas (e.g., blocks or block
groups), (3) listing units within subareas, (4) age domains within
sampled listing units, and (5) eligible individuals within sampled age
domains. The 1998 NHSDA used the same 115 PSUs selected for the 1995
through 1997 NHSDAs, 6 supplemental PSUs from Arizona and California,
and an additional 16 noncertainty PSUs from 13 purposely selected
states. The 115 PSUs were selected to represent the nation's total
eligible population, including areas of high Hispanic concentration.
These PSUs were defined as metropolitan areas, counties, groups of
counties, Census tracts, and independent cities. Of the 115 PSUs, 43 were selected
with certainty and 72 were randomly selected with probability
proportional to size (PPS). The national sample was supplemented by a
PPS selection of four noncertainty PSUs from Arizona plus two noncertainty
PSUs from California. The additional 16 noncertainty PSUs were added in States with a small sample size to increase the reliability of estimates. Because the national sample provided
representation for certainty PSUs in each state, no additional
certainty PSUs were added to either sample. The 1998 NHSDA used all
available segments that had adequate listing units from the 1997
NHSDA. Only 24 percent of the 1998 sample, or 640 segments, consisted
of a new segment sample selected for the 1998 NHSDA. The remaining 76
percent, or 2,030 segments, overlapped with the 1997 survey year. The
five age groups were: ages 12-17, 18-25, 26-34, 35-49, and 50 and
older. The three race/ethnic groups were: whites/others, non-Hispanic
Blacks, and Hispanics. Blacks and Hispanics were oversampled in the
115 PSUs that comprised the national study component. There was no
oversampling of Hispanics in the Arizona/California supplement because
each state's Hispanic allocation in the national study component was
large enough to satisfy state-level precision requirements.
Consequently, the three racial/ethnic groups were sampled in the
supplement so that the combined national study and supplemental
samples would result in a proportionally allocated sample.
Mode of Data Collection:
computer-assisted personal interview (CAPI),
The study yielded an 85.4 percent completion rate
for screening sample households and 93.0 percent for screening
eligible households. The interview response rates for the three
racial/ethnic groups were: 74.1 percent for whites/others, 79.7
percent for Blacks, and 80.5 percent for Hispanics. The overall unweighted
interview response rate was 77 percent. A completed interview had to
contain, at a minimum, data on the recency of use of marijuana,
cocaine, and alcohol.
Extent of Processing: ICPSR data undergo a confidentiality review and are altered when necessary to limit the risk of
disclosure. ICPSR also routinely creates ready-to-go data files along with setups in the major
statistical software formats as well as standard codebooks to accompany the data. In addition to
these procedures, ICPSR performed the following processing steps for this data collection:
Performed consistency checks.
Created online analysis version with question text.
Performed recodes and/or calculated derived variables.
Checked for undocumented or out-of-range codes.
Restrictions: Users are reminded by the United States Department of
Health and Human Services that these data are to be used solely for
statistical analysis and reporting of aggregated information and not
for the investigation of specific individuals or treatment