National Institute of Mental Health Schizophrenia Collaborative Study

Description

In the NIMH Schizophrenia Collaborative Study, patients were randomized to receive one of four medications, either placebo or one of three different anti-psychotic drugs. The protocol indicated subjects were to then be evaluated at weeks 0, 1, 3, 6 to assess severity of illness; additionally some measurements were made at weeks 2, 4, and 5. The dataset was taken from mixor package which unfortunately is no longer on CRAN. This is a data frame with 1603 observations on the following 9 variables.

• id: a numeric vector indicating the unique patient identifier
• imps79: a numeric vector from item 79 on the Inpatient Multidimensional Psychiatric Scale indicating severity of illness. The scores were applied to be interpreted as follows: 1 = normal, not ill at all; 2 = borderline mentally ill; 3 = mildly ill; 4 = moderately ill; 5 = markedly ill; 6 = severly ill; 7 = among the most extremely ill
• imps79b: a needless binary version of imps79
• imps79o: an ordinally scaled version of imps79
• int: a numeric vector of ones; used in stand-alone package to indicate intercept
• TxDrug: a numeric vector indicating treatment with drug (1) or placebo (0)
• Week: a numeric vector indicating time, in weeks
• SqrtWeek: the square root of the Week variable
• TxSWeek: a variable representing the TxDrug x Week interaction

References

• Hedeker D. and Gibbons R.D. (1996) A computer program for mixed-effects ordinal regression analysis. Computer Methods and Programs in Biomedicine 49, 157-176.
• Hedeker D and Gibbons R.D. (2006) Longitudinal Data Analysis, Wiley, Hoboken, New Jesery.