In 1989, the question for SCHIZYR was part the mental health section of the survey. The Field Representative's Manual instructed interviewers to explain to respondents that for this series of questions, "no one else needs to be present" though it unclear if such condition was mandatory for this part of the interview. The Manual does not provide a definition for "schizophrenia " and the term is assumed to be respondent defined.

In 1994 and 1995, this variable is part of the Disability Supplement (NHIS-D) that collects information on disability. NHIS-D included two household interviews: in Phase I all members of sample families were screened for any indication of disability; in Phase II persons with any indication of disability were followed-up for additional information. Phase I includes sensory, communication, and mobility problems; health conditions; activities of daily living and independent activities of daily living; functional limitations; mental health; services and benefits; special health needs of children; early child development; education; relationship to respondent; and perceived disability. Phase II includes four Disability Followback Survey (DFS) questionnaires: one for children, one for adults, one for elderly persons (69 years of age and over) without any indication of disability (also called the Supplement on Aging or SOA; only in 1994), and one for persons with a history of polio.

For 2007, SCHIZEV identifies sample adults who were ever by a health professional that they had Schizophrenia