Am J Psychiatry 1993; 150:1386-1391
Copyright © 1993 by American Psychiatric Association
The abnormality of normal comparison groups: the identification of psychosis proneness and substance abuse in putatively normal research subjects
RW Butler, MA Jenkins and DL Braff
Department of Pediatrics, Memorial Sloan-Kettering Cancer Center, New York, NY 10021.
OBJECTIVE: Careful assessment of research subjects is important because the
inclusion of subjects who manifest psychopathology and significant
substance abuse in normal comparison groups will decrease statistical and
experimental power. The current study evaluated the usefulness of an
MMPI-derived algorithm in identifying tendencies toward psychosis and
substance abuse in putatively normal research volunteers. METHOD:
Ninety-eight adults who were recruited as normal comparison research
subjects completed the MMPI, psychiatric interviews, questionnaires, and
selected neuropsychological tests. The MMPI classified 81 presumed normal
subjects into four subgroups: 1) not psychosis prone/substance abuse not
likely, 2) not psychosis prone/substance abuse likely, 3) psychosis
prone/substance abuse not likely, and 4) psychosis prone/substance abuse
likely. RESULTS: The MMPI psychosis-prone and substance abuse factors
identified significantly distressed and dysfunctional individuals with a
relatively high degree of accuracy. CONCLUSIONS: It is becoming
increasingly apparent that the cursory self- report screening of normal
subjects may result in unacceptable levels of psychopathology in comparison
groups. The current results also indicate that an adequate substance abuse
evaluation is extremely important and that brief self-report information
may be misleading. Empirically derived assessment tools, such as the MMPI,
may prove useful in allowing researchers to more accurately define control
parameters and group membership.
