Subject selection for the placebo- and comparator-controlled trials of neuroleptics in schizophrenia

Pavel Mohr, Pál Czobor

Research output: Contribution to journalArticle

23 Citations (Scopus)


It has been suggested that inclusion of a placebo treatment arm in controlled clinical trials might bias the selection of study subjects. Presumably, patients in the placebo-controlled studies are more stable, but there are no data available to support such an assumption. The authors tested the hypothesis in a set of randomized trials of neuroleptics in treating schizophrenia by comparing placebo-controlled (PCTs) and comparator- controlled trials (CCTs) in terms of basic patient characteristics. The results, based on a total of 296 studies, showed that the patients in PCTs, compared with those in CCTs, were older (p < 0.002), had a longer duration of illness (p < 0.001), and a lower initial symptom severity (p < 0.02). No difference was found in the number of subjects per treatment arm or in the proportion of female subjects. However, investigation of studies which used same-gender study subjects revealed that female-only populations were more likely to be tested in PCTs (p < 0.03) than in CCTs. To investigate current trends in psychopharmacologic research, the authors tested separately a subset of trials of new atypical antipsychotics. The results indicated a significantly smaller number of females participating in the latest PCTs (p < 0.0003). Moreover, our findings suggest that the characteristics of patients in the current controlled trials are rather uniform; thus, the generalizability of new study findings for certain groups of patients with schizophrenia (e.g., with early or late onset or brief duration of illness) may be compromised.

Original languageEnglish
Pages (from-to)240-245
Number of pages6
JournalJournal of Clinical Psychopharmacology
Issue number2
Publication statusPublished - Apr 1 2000


ASJC Scopus subject areas

  • Psychiatry and Mental health
  • Pharmacology (medical)

Cite this