The NESARC data were collected to obtain a representative national sample of US adults. In wave 1 (2001–2002), face-to-face interviews were completed with 43 093 persons aged 18 years or older. The overall response rate was 81.0%. The wave 1 sample was reinterviewed in wave 2 (2004–2005) 3 years later (mean interval =36.6 months, SE=2.62), with a response rate of 80.4% (N=34 653) based on the wave 1 sample. The NESARC sample size was chosen to be sufficiently large to produce nationally representative proportions for the study of substance abuse and dependence and mental disorders by demographic group with CIs equal to or smaller than extant studies. Following NESARC guidelines,24 25 the original NESARC data set was transformed to account for survey design effects and sampling weights upon responses in order to adjust for sample selection procedures, non-response from selected households or individuals, oversampling (of young adults, blacks and Hispanics) and non-response at the wave 2 time point. Those weights and survey design effects, employed in other studies based on NESARC data, as well as other methodological details of waves 1 and 2 are described in published NESARC Source and Accuracy Statements.24 25
