Ventriculomegaly in schizophrenia: is the choice of controls important?

The issue of adequate controls for the study of ventriculomegaly in schizophrenia has been explored initially by Andreasen et al. (1982), who proposed that healthy volunteers, a group with presumably smaller ventricles than medical controls, be considered the optimal comparison group in this area of research. Recently, Smith and Iacono (1986) suggested that group differences may appear to be greater when controls who are patients are used, as a result of the systematic exclusion of medical patients with large though normal ventricles. We conducted a meta-analysis of 37 studies of lateral ventriculomegaly in schizophrenia to clarify this issue. The results indicate that the average effect size in studies with healthy controls does not differ significantly from that obtained in studies employing medical, neurological, or psychiatric (nonpsychotic) controls. Thus, any group without gross neurological damage or severe psychopathology may be used for establishing ventriculomegaly in schizophrenia.