We include all diaries from original surveys in the MTUS. While the MTUS 0-weights bad quality diaries not suitable for many forms of analysis, these diaries are in the files for users to consider during research.
If you are matching MTUS variables to original surveys, keep in mind that the MTUS stores adult diaries (aged 18+) separately from the child diaries (aged <18). You will need to merge the child files (if there are child diarists in the survey) with the adult diaries before merging with variables from the original survey.
MTUS does not include information on people who do not complete a diary but for which an original survey may have collected information.